BR102012012197A2 - SCHIFF REAGENT STABILIZATION METHOD IN VARIOUS VEHICLES, SCHIFF REAGENT IMMOBILIZED IN SOLID MATRIXES, PROCESS OF IMPREGNATION OF THIS REAGENT, FOR METHODS OF METHODIZATION OF THE SPECIFIED BASE METHODS COMMERCIAL PRODUCTS AND THEIR APPLICATIONS - Google Patents

Abstract

METHOD OF STABILIZING THE SCHIFF REAGENT IN VARIOUS VEHICLES, SCHIFF REAGENT IMMOBILIZED IN SOLID MATRICES, IMPREGNATION PROCESS OF THIS REAGENT, ANALYTICAL DETERMINATION METHOD OF DETERMINING METHOD OF DETERMINATION COMMERCIAL PRODUCTS AND THEIR APPLICATIONS. The present invention relates to a method of stabilizing the Schiff Reagent in several vehicles (liquid or solid), useful in the colorimetric determination of the presence or absence of specific compounds in a sample, especially aldehydes and alcohols. Obtaining this stabilized reagent, especially those immobilized in solid matrices, such as metal and non-metal oxides, cellulosic materials and polymers, allow the analysis to be carried out in the field or in places of interest, in addition to facilitating the analysis by ordinary users or in methodologies. that already use this reagent prepared in a conventional way. Another aspect addresses the development of a qualitative and semi-quantitative colorimetric analysis method for these compounds, and a kit for analytical determination in the field, especially methanol and / or formaldehyde, in commercial products such as fuels, liquid solvents and alcoholic beverages, as well as the analysis of formaldehyde in cleaning, cosmetics and personal hygiene and sanitizing products, as well as its applications.

Description

SCHIFF REAGENT STABILIZATION METHOD IN DIFFERENT VEHICLES, SCHIFF REAGENT IMMOBILIZED IN SOLID MATRIXES, PROCESS OF IMPREGNATION OF THIS REAGENT, METHOD OF DETERMINING ANALYTICS DETERMINED BASE METHODS DETERMINED IN COMMERCIAL PRODUCTS AND THEIR APPLICATIONS

FIELD OF INVENTION

The present invention relates to a method of stabilizing the 10 Schiff Reagent in various vehicles while preserving its characteristics used in analytical determination techniques, especially in colorimetric determination of the presence or absence of specific compounds in a given sample, especially aldehydes and alcohols. . Obtaining such a stabilized analytical reagent in liquid or solid form allows for field analysis, besides operationally facilitating the analyzes already using this conventionally prepared reagent, being objects of the present invention the stabilized Schiff Reagent, mainly immobilized in solid matrices and their impregnation process on different substrates, for example metal and non-metal oxides, cellulosic materials, polymers, among others.

Another aspect of the invention involves the development of a method of analytical determination of samples based on the use of at least one proposed Schiff's Reagent, particularly in the determination of alcohols and aldehydes.

In one of its embodiments, the present invention provides for the elaboration of a portable kit containing reagents and materials capable of colorimetrically determining, by instructions, the presence and / or viability of quantifying aldehydes and alcohols, especially methanol in commercial products such as as liquid fuels and alcoholic beverages, as well as formaldehyde in products such as cosmetics, cleaning products and personal hygiene. The application of the kit allows analysis in the field or in places of interest, such as gas stations, or qualitative and / or semi-quantitative analyzes of samples of these commercial products suspected of contamination of methanol and / or formaldehyde. point of sale or analysis prior to consumption or quality control mainly in the distribution of liquid and combustible solvents. One of the objectives of the present invention is to quickly and easily indicate in the field whether or not methanol and / or formaldehyde is present in commercially distributed products, avoiding the cost of specialized, time consuming and expensive analyzes, which are performed only in laboratories, also facilitating how to analyze samples so as to dispense with skilled labor.

Although Schiff's Reagent is known for qualitative detection of aldehydes and selective detection of methanol in ethanol by prior oxidation, the developed analytical methodology is applicable for a wide range of samples. These samples consist of commercial products, mainly 10 where methanol or formaldehyde are considered to be adulterating or contaminating ingredients, harmful to consumers' health, and specific detection methods developed using solution-supported or solid-material Schiff Reagent are aimed at facilitate its handling and improve its stability. In addition, these analysis methods, including the Kit and the use of at least one of the proposed Schiff Reagents, allow the identification of the presence or absence of specific ingredients for the purpose of verifying the framing of the analyzed product against legal particulars ( specifications) and service / product control practices in the supply and / or distribution and / or purchase / sale of the commercial product of interest, and further extending to use in conventional analysis practices where this reagent is already used, as for example in organic analytical tests and application as a dye or color change agent in biological systems.

TECHNICAL STATE

Liquid fuels used in internal combustion engines such as hydrous alcohol and gasoline are likely to be tampered with methanol. The first is entirely 96% ethanol and the second has between 20 and 25% anhydrous ethanol in its composition. Due to the lower market price of methanol relative to ethanol and the physicochemical similarities between them, adulteration has been practiced alarmingly, for example up to 30 100% for hydrated alcohol. The National Petroleum Agency (ANP), according to ANP Resolution No. 7 of February 9, 2011 (DOU February 10, 2011 - and rectified by DOU April 14, 2011), defines as a limit amount of methanol. present in anhydrous or hydrous ethanol at a rate of 1%, the only analysis being regulated by gas chromatography, which is an impractical technique to perform when receiving the fuel charge at the stations. As the ANP considers ethanol to be a regulated fuel for use, it adopts the addition of anhydrous ethanol to gasoline, but methanol additions to gasoline may also occur, promoting adulteration, which removes this fuel from the required specification, which is a problem. already experienced at gas stations. In addition to not being standardized by the ANP as a fuel, methanol is toxic to human health and can cause various ills ranging from liver and vision problems, even causing death. Therefore, methanol-containing alcoholic beverages 10 are highly toxic and monitoring is required for the presence of methanol in beverages.

Formaldehyde has always been used in various commercial personal care and cleaning products for the purpose of preservative and disinfectant. In addition to being used in cosmetics and beauty salons, mainly for 15 hair straightening purposes. The National Health Surveillance Agency (ANVISA) has recently banned its use in sanitizers in accordance with RDC Resolution No. 35, published on June 3, 2008, as well as restricted its marketing in accordance with RDC Resolution No. 36. , published June 17, 2009. ANVISA also banned and made reservations about the use of formaldehyde 20 in beautification treatments in view of presenting various side effects, such as physical damage and malaise of users. Additionally, it is well known that formaldehyde has a proven carcinogenic effect, which is why the changes in legislation regarding its use in different commercial products were based.

Due to the similarity of properties between methyl and ethyl alcohols,

The use of spectroscopic or chromatographic techniques is necessary to identify both in a sample. One widely used technique is high performance liquid chromatography (HPLC). An example application of this methodology has been described for detecting and quantifying 30 methanol in a system containing ethanol and water (Chen, S.H., et al. J. Chromatogr: A., 1998, 799, 93). Recently, a method for quantifying methanol in mixtures containing ethanol and water using the Infrared technique has been reported (Carneiro, H. S. P., et al. Energy & Fuels, 2008, 22, 2767). Both methodologies are accurate for the detection and determination of the ethanol / methanol mixture, but they require specific equipment, and the chromatography device in particular is expensive to maintain and both need skilled technicians for its operation. These techniques are performed in laboratories 5 with specialized infrastructure, and their application in the field is not advantageous, that is, in places without the proper laboratory infrastructure, such as those found in those where these products are sold, such as gas stations, fuel dispensers. carbonated or non-carbonated alcoholic beverages, loading / unloading points, beauty salons or other places of interest. There are currently small equipment for spectroscopic and chromatographic analysis in the field, such as small infrared equipment. However, they require specialized technicians for their operation, as well as high maintenance and upkeep costs, which is why they are not widespread.

In order to overcome these difficulties, it is necessary to employ a

simpler technique, without the use of sophisticated equipment (spectroscopic or chromatographic) and which generates results quickly and with simple interpretation, with reproducibility and efficiency, such as colorimetric methods, being one of the objects of the present invention.

Benchtop techniques for methanol analysis in ethanol directed to

Alcoholic beverages were developed in the early twentieth century. Previously, several methods were performed, however, they were poorly selective methods and very susceptible to false positives, besides using complex methodologies and restricted reagents, such as alkaloids. The methodology employing the modified 25 Schiff Reagent, later enhanced by RM Chapin, was at the time the most robust and selective interfering technique for both qualitative and quantitative detection of methanol in ethanol (Deniges, G., Compt (1910, 150, 832; Chapin, RM, J. Ind. Eng. Chem., 1921, 13, 543).

Appropriate methods for methanol analysis in ethanol were discussed and use the modified Chapin RM method for methanol detection, but restricting his field of research to alcoholic beverages, which he listed a number of interferers in the procedure (Georgia, FR, et al. Ind. Eng. Chem., 1926,

18, 304). Subsequently, the ISO 1388 / 8-1981 (E) standard was published using a simplification of the method modified by R. M. Chapin for the determination of methanol in ethanol for industrial use using colorimetric analysis. However, the standard does not expand to other sample types, such as fuels and beverages, and its detection range is limited to 5 contaminations of 0.10 to 1.50% methanol in the sample. The standard also uses too many dilutions in sample preparation and does not alert you to possible problems caused by how the Schiff Reagent should be stored. Thus, the aforementioned bench methods are very technical, so they need at least one skilled technician for the application of the technique, as well as a suitable laboratory infrastructure for its implementation.

Several papers have been published using the Schiff Reagent methodology for the detection of methanol (MeOH) in beverages, such as the colorimetric method described for the determination of MeOH in alcoholic beverages and vodka based on the oxidation of methanol to formaldehyde with potassium permanganate (KMnO4) in the presence of sulfuric acid (HaSO4); the excess added permanganate is then bleached with oxalic acid (HOOCCOOH), and the formaldehyde (CH2O) formed is treated with Schiff's Reagent to give a blue-gray complex, which is quantified by photoelectrochorimetry at 582 nm. The method is accurate, reliable and requires 1 mL of beverages (Filatova, T. et al. Fermentnaya i Spirtovaya Promyshlennost, 1982, 7, 13). In another study, related to the determination of methanol in beverages, the method of indirect identification of methanol via prior formaldehyde oxidation was employed, the analysis was performed using chromotropic acid (Skapska, S. et al. Przemysl Fermentacyjny 25 i Owocowo-Warzywny , 1998, 42, 41). In the same vein as the aforementioned articles, a very comprehensive work has been carried out for the determination of methanol in musts, wines, distillates and fruits employing four different procedures. This work brings a wide critical evaluation of methods for detecting MeOH by colorimetry with Schiff's reagent, chromotropic acid colorimetry and polarography (Tuszynski, T., Bromatologia / Chemia Toksykologiczna, 1989, 22, 110). It is important to note that the literature does not specifically refer to rum and beer analysis, noting that the analytical sample determination method based on the use of at least one proposed Schiff Reagent (stabilized reagent) and the kit for the determination of alcohols, mainly methanol, proposed in the present invention, when applied to these products, showed very promising results in terms of reliability.

Regarding patent processes related to the use of

Schiff Stably or in their use in making kits for analysis of alcohols and aldehydes, the examples to be cited are:

US20030220191 discloses a modified Schiff Reagent that is stable at room temperature for aldehyde determination in biological samples. The reagent comprises potassium metabisulphite, p-rosaniline acetate and hydrochloric acid (HCl). Potassium metabisulphite and p-rosaniline acetate are present in the reagent in equal amounts, with reagent pH ranging from about 1.2 to about 2.7. The stability of the described Schiff Regent is different from that presented in the present invention.

US200607360 describes a kit consisting primarily of

Schiff for detecting aldehydes in biological samples such as urine and blood.

It should be noted that there is no record of portable kits for methanol analysis in general commercial products, especially fuels and beverages, as well as for the analysis of the presence of formaldehyde in commercial products, including cosmetics, cleaning and personal care products and sanitizing products.

Currently, the use of Schiff Reagent is focused on organic analytical tests for aldehyde detection and application as a dye in biological systems. Recently, Schiff's Reagent was impregnated with porous glass and this material was used to detect the presence of aldehydes in the atmosphere. In the reviewed literature, no material has been impregnated to detect the presence of aldehydes in commercial products (Maruo, Y. Y., et al. In Sensors and Actuators B, 2008, 129, 544) as proposed in the present invention.

Although the literature brings together a range of spectroscopic or chromatographic techniques for the identification of methanol and formaldehyde in different samples, it is believed that they do not apply for field analysis as they require expensive equipment and are performed only in laboratories, with the need for skilled labor, demanding time to obtain results, even if only qualitative. Thus, the present invention is directed to a method which makes it possible, quickly and easily, to indicate especially the presence or absence of methanol and / or formaldehyde in commercial products meeting required specifications or in stage 5 service / product control practices. supply and / or distribution and / or purchase / sale, avoiding the cost associated with performing specialized analyzes.

It is believed that the lack or non-diffusion of colorimetric analysis practices of alcohols and aldehydes, specifically methanol and formaldehyde, based on the use of Schiff's Reagent and for field implementation, as well as a wide range of application (products). in general) is mainly due to the stability of this reagent. It is well known in the art that this reagent is unstable over time due to evaporative loss of SO2. The stability of the Schiff Reagent variants is known to be directly affected by its loss of SO2. When this loss is large and at a rapid rate, the reagent stability decreases until it deteriorates, losing its reactive property of analytical interest, limiting the accuracy, reliability or reproducibility factors of its use, especially in the manufacture of analysis kits or portable alcohol and aldehyde analysis kits. Accordingly, various methods have been used to prevent SO2 loss and increase the stability of this reagent over time. Some examples are: methods involving storing the reagent in a stoppered vial at a low temperature; or involve minimizing evaporation of SO2 by covering the reagent surface, such as with xylene or mineral oil.

To avoid these problems and the use of other supplies for storage of this reagent (increased cost and possibility of contamination) a widely used laboratory practice is the periodic preparation of the Schiff Reagent solution, which is kept refrigerated for relatively long periods. short (a few days). However, this practice has technical operational limitations, mainly related to the necessary equipment and requiring 30 qualified manpower, since it depends on the decision on the viability of the stored reagent and its preparation in a proper way to perform the intended analytical test.

All of these methods have contributed to the control of SO2 loss. However, there is still a need to maintain the level of SO2 in the Schiff Reagent and thus the stability or reaction properties of that reagent for a considerable period of time.

The present invention satisfies this need and solves the aforementioned problems by providing a sensitive reagent which is stable over a substantial period of time for accurate and reliable analysis where its durability is greatly increased.

In the present invention an improvement in the storage form of the Schiff Reagent was made, avoiding the loss of SO2, being stabilized in several vehicles in liquid form (as in aqueous solution, properly packed in vacant or vacant containers) or solid (such as impregnated with solid matrices that allow its activity (color indicative for the presence of alcohols or aldehydes, mainly methanol or formaldehyde), exemplified by cellulosic material (eg paper), glass, organic polymers (eg a polysaccharide such as starch) and metal and non-metal oxides (eg aluminum oxide (AI2O3) or simply alumina; silicon oxide or silica). In these cases studies also show that as an additional caution It is recommended to avoid exposure of Iuz to prevent decomposition reactions in order to maintain reagent activity. proposed Schiff Reagent for more than 2 months. In general, the form of production and storage of such reagents is of greater relevance in this regard and should be packed (solid) or filled (liquid) in closed containers without vacant space. In the case of solutions of these reagents, there is the possibility of single dose use, further contributing to the question of operational practicality applicable to any user.

The elimination of vacancy spaces extends to the proposed methodologies based on the use of at least one of the stabilized Schiff Reagents and their applications. It is also considered as a final step in the method of impregnating this reagent in solid matrices, including simple practices such as packaging of solid reagent strips or plates in plastic films.

Thus, the main advantages of the objects of the present invention include: - Reliable qualitative test for the detection of aldehydes and alcohols, mainly formaldehyde and methanol, in a considerable range of commercial products, especially liquid fuels and solvents, carbonated or non-carbonated alcoholic beverages. , cosmetics, personal cleaning and sanitizing products;

- possibility of accurately detecting methanol in samples

with quantity variations from 0 to 100%, mainly for liquid samples;

- Reliable semi-quantitative test for detection as presented for the qualitative test using known techniques and instrumentation using

comparison with known standard solutions and according to the ingredient to be tested;

- Provision of different presentations of solid phase stabilized Schiff Reagent: paper tapes, powder, gel, among others;

- possibility of using Schiff Reagent in solution and impregnated in solid matrices without the need for storage under refrigeration;

- applicable to a wide range of commercial products, where mainly methanol and / or formaldehyde are considered to be adulterating or contaminating or harmful to consumers' health;

- field detection products and methodologies, enabling stable use of Schiff Reagent over considerable periods of time (over 2

months);

- Systematic and reliable dissemination of qualitative and / or semi-quantitative field analysis in a practical way by any user, using methodologies based on the use of Schiff's Reagent already established by the technique, especially those that

involve dilution of the sample in water (product to be analyzed;

- Possibility of refilling and / or refilling the analytical reagents that make up the portable kit, especially in the case of solution stabilized Schiff Reagent;

- possibility of using proposed solid phase Schiff Reagents without contaminating the sample during detection analysis, providing the same

for later use or other tests to be performed, especially in the case of tapes of cellulosic material or paper with this impregnated reagent;

- possibility of using immobilized silica gel Schiff Reagent, which has the same functionality as glass, but is a more economical option;

- Possibility of using the proposed Schiff Reagents, especially the

impregnated in solid matrices, in conventional analysis practices where this reagent is already used, such as organic analytical tests, verification of contaminants in the atmosphere and use as a dye or color change agent in biological systems.

BRIEF DESCRIPTION OF THE FIGURES

The invention may be better understood from Figures 1 to 8, the description of which follows below:

Figure 1: Example of the kit of the present invention in front perspective view in: (a) schematic representation and (b) photograph, where: (A) lid (s), (A.1) 15 being a foldable lid disposed on the side superior to the case and (A.2) on the front side to it; (B) the space to accommodate the vials containing the solutions for analysis which are coupled to a dispenser represented by (J); (C) represents the space to fit the element (D); (D) is a removable drawer with compartments (E and F); (E) space to fit the element (G); (F) space to accommodate the vials containing the liquid or solid stabilized Schiff Reagent of the present invention; (G) rack for test tubes; (H) space to accommodate the pipettor; (I) space to accommodate the kit manual (s) and pipettor tips; and (J) a dispenser coupled bottle.

Figure 2: Representation of the qualitative test for methanol in 95% commercial ethyl alcohol using 0, 10, 25, 50, 75 and 100% contamination, respectively from left to right, along with increased bluish-violet coloration.

Figure 3: Representation of the qualitative test for methanol in hydrated gas station alcohol using 0, 10, 25, 50, 75 and 100% contamination respectively from left to right, along with increased bluish-violet coloration. Figure 4: Representation of the qualitative test for methanol in commercial gasoline, using 0 and 50% contamination respectively represented from left to right, along with increased bluish-violet coloration.

Figure 5: Representation of the qualitative test for methanol in commercial cachaça, using 0, 1, 5, 15 and 30% contamination respectively from left to right, together with the increase in bluish-violet coloration.

Figure 6: Representation of the qualitative test for methanol in commercial beer, using 0, 1, 2 and 5% contamination respectively from left to right, together with increased bluish-violet coloration.

Figure 7: Representation of the qualitative test for formaldehyde in commercial hair shampoo using 0, 1, 2 and 5% contamination respectively from left to right, together with increased violet coloration.

Figure 8: Representation of the qualitative test for formaldehyde in commercial general cleaning detergent using 0, 1, 2 and 5% contamination respectively from left to right, along with increased violet coloration.

DESCRIPTION OF THE INVENTION

The present invention is related to the development of a method of stabilizing the Sdiiff Reagent in various vehicles to obtain this stabilized reagent in liquid or solid phase, maintaining its color changing agent characteristics, when in the presence of specific compounds, which are present in the present invention. They are used for analytical assays for colorimetric detection of aldehydes and alcohols in different sample types.

The formation of Schiff's Reagent results from the reaction of a specific dye.

with sulfite in acidic medium. The precursor of Schiff's Reagent is a dye belonging to the basic fuchsin class called p-rosaniline. Hydrochloric p-rosaniline in aqueous and acidic state generates a central tertiary carbocation, stabilized by a chloride ion, conjugating the aromatic systems bound to 30 and generating visible absorption around 539 nm, and thus providing a rosy tone. the solution (Gibson, LT, et al., Analytica Chimica Acta, 623, 2008, 110). For the formation of Schiff's Reagent p-rosaniline reacts with sulfite in acidic medium. Protons fall into the amino groups and sulfite binds to the central carbon. The effective bonding of carbocation center with sulfite promotes the breakdown of the system conjugation, so that the reagent no longer absorbs in the visible, becoming colorless.

When Schiff's Reagent reacts with the aldehyde present in solution, the

Sulfite bound to the central carbon returns to solution regenerating the central carbocation, re-establishing the system conjugation and concomitant absorption in the visible. However, due to the presence of aminosulfonic groups formed in the reactant amino groups during the reaction, the wavelength at which it is absorbed shifts 10 to approximately 588 nm, generating a new color in the purple-tone solution related to the presence of aldehyde. in the sample.

Oxidation to identify methanol in ethanol is performed in two steps. First the sample amount is adjusted to 5% by diluting with water in view of the allowable ideal of alcohol in the analysis (Chapin, R. M., J. Ind. Eng. 15 Chem., 1921, 13, 543). The first step consists in the oxidation of the present alcohols to aldehydes using potassium permanganate (KMnO4). In this step, in addition to aldehydes, manganese oxide (MnO2) 1 is formed, a brown solid that is suspended in solution. In the second step, a solution of oxalic acid (H00CC00H) and sulfuric acid (H2SO4) 1 is used to increase the acidity of the medium and to transform the MnO2 into the colorless Mn2 + ion in solution. Finally, add Schiff's Reagent and check the color formed.

In both cases (determination of aldehydes and alcohols) excess acid in the sample impairs the formation of the colored adduct with the aldehyde. Lack and excess sulfite in solution also interfere with adduct formation. Parallel reactions of sulfite addition to the aldehydes present in solution also influence the process. The system does not stabilize due to parallel reactions, constant loss of generally volatile aldehyde, and volatilization of SO2 so that temperature greatly influences the system.

In the present invention, due to the loss of SO2, the Schiff Reagent should preferably be kept cool and in a closed container with no vacant space. Also, as an additional caution, it is recommended to avoid exposure of Iuz to prevent decomposition reactions in order to maintain the activity of this reagent.

In general, the Schiff Reagent stabilization method in various liquid or solid vehicles comprises the steps of:

(a) Prepare a homogeneous solution of Schiff's Reagent by mixing by mass its constituents represented by: a basic fuchsin

(range from about 0.02 to about 0.9%), a source of sulfite (range from about 0.05 to about 1.8%) and an acid;

b) Pack the solution in appropriate packaging or containers, without vacancy spaces; or

c) Place the solution obtained in step a in contact with dies or

solid substrates for a period and then dry them.

The preparation of Schiff's Reagent solution (step a) is made according to established techniques by mixing the respective solutions of their precursor components. The components of the Schiff Reagent used were: a basic fuchsin, preferably p-rosaline; - a source of sulphite selected from sodium metabisulphite, sulfur dioxide, sulphorous acid, among others, with sodium metabisulphite being preferred; and a mineral acid selected from sulfuric acid, hydrochloric acid, among others, with sulfuric acid being preferred.

In liquid phase, for example, aqueous solution, the reagent is stabilized by steps a and b, resulting in ready-to-use products.

In solid phase, the obtained products (immobilized Schiff Reagent) result from the application of steps a and c. Impregnation (step c) depends on factors linked to the type of matrix or solid substrate used to obtain tapes, plates, powders, gels, among others. The solid matrices used should have the desirable characteristics of: not reacting with Schrff's Reagent, supporting it on its surface without changing its reactivity and not presenting colors that interfere with the colorimetric analysis, before and after the addition of Schiff's Reagent. Examples of solid matrices are: - metal and non-metal oxides (silica, alumina, etc.), - cellulosic materials (paper and its derivatives, among others), - polymers (plastics, among others).

In this case, the drying is performed by techniques already established, being

Temperature control (preferably below 20 ° C) is required for reagent stability reasons, especially to avoid SO2 losses. The choice of drying process also depends on the type of solid matrix obtained and its presentation (tape, plate, powder, gel, etc.).

Still for the solid phase, reagent stabilization is complemented by the use of packages without vacancy spaces.

This stabilization method is also considered to be a Schiff Reagent preparation method in which specific restriction storage steps are included and any type of packaging or flasks is used, provided it is inert to the reagent and allows for structural shape modeling. not to have vacant spaces with the contents inside, ie, free or empty spaces between the reagent solution (or reagent immobilized in solid matrices) and the container (or packaging) after preparation.

This way of obtaining this analytical reagent allows the availability of different products considered as Schiff's Reagent with different presentation forms (eg solution, tape, plate, powder and gel) with extended analytical durability, allowing for field analysis. as well as operationally facilitating on-site analysis or analyzes already using this conventionally prepared reagent (colorimetric analysis techniques for detecting aldehydes or dyes in biological systems), extending the range of 20 applications. These characteristics also allow the manufacture of aldehyde and alcohol determination kits, mainly formaldehyde and methanol, with the possibility of using this liquid reagent in refill or refillable presentation forms for single dose use.

In the Examples, the stabilized Schiff's Reagent as proposed in the present invention, such as paper strips, powders and silica gels had durability times greater than 2 months. Complementary storage procedures such as refrigeration and light protection aim to further extend the shelf life of this reagent.

Another aspect of the present invention relates to the stabilized Schiff Reagent obtained as described above, especially those immobilized on solid matrices and their impregnation process. These immobilized reagents refer to tapes, plates, rods or any suitable solid substrate containing homogeneously distributed Schiff's Reagent, which changes color in the presence of aldehydes or alcohols, mainly formalin and methanol (violet color). The powders and gels also have such a detection property and are used in this way or adhered to other substrates to facilitate handling.

When used for analysis, impregnated reagents interact with the analysis either on the surface of the material or migrating to the sample if submerged in the analyte, generating color (eg, violet for presence and red or pink for methanol). or formaldehyde). Also considering the impregnated reagent, in the absence of the analyte no color is generated from the Schiff Reagent, except in the presence of reagent dilution in which red or rosacea are formed.

The use of the proposed solid phase Schiff Reagents of the present invention still has the advantage that it does not contaminate the sample during detection analysis, making it available for later use or other testing, which is very important for available samples. in restricted quantity. This is the case for tapes of cellulosic material, eg paper, where detection can also be performed by dripping the sample onto it and observing the change in its color.

Schifff's Reagent is stably impregnated on paper and silica gel. The cooled materials remained colorless and active for detecting aldehydes for up to three months after preparation, when properly stored. Their use also generates positive tests for the detection of formaldehyde in real samples used in the example analysis kit shown in Figures 1a and 1b.

In general, the process of impregnating this reagent in matrices or solid substrates depends on the intrinsic properties of the materials used, resulting in immobilized Scniff Reagent-based analytical detection products, represented by tapes, plates, powders, gels, among others. The desirable characteristics of these matrices or substrates were previously described in the proposed stabilization method for this reagent (steps a and c). The contact of the homogeneous reagent solution 30 with the solid matrix used favors the physical and / or chemical adsorption processes on its surface, emphasizing that drying is preferably done at temperatures below 20 ° C, due to the stability of the Schiff's reagent. In the case of cellulosic material, especially paper, the Schiff Reagent impregnation process comprises the steps of:

A) Fully immerse appropriately sized cellulosic material into a homogeneous Schiff Reagent solution prepared by mixing a fuchsin

(around 0.02 to about 0.9%), a source of sulfite (around 0.05 to about 1.8%) and a mineral acid (around 0.07 about 2.2%);

B) Remove the cellulosic material from the previous system and promote its drying.

C) Store it properly after drying.

The components of the Schiff Reagent used were: a basic fuchsin,

preferably p-rosaline; - a source of sulphite selected from sodium metabisulphite, sulfur dioxide, sulphorous acid, among others, with sodium metabisulphite being preferred; and a mineral acid selected from sulfuric acid, hydrochloric acid, among others, with sulfuric acid being preferred. The above mentioned cellulosic material 15 refers to any substrate consisting of cellulose or a derivative, which may be new or recycled paper, manufactured or waste products such as chips generated in general industrial processes.

In the Example, the cellulosic material used was a 5 cm by 5 cm plain filter paper sheet. Drying was performed in a local atmosphere, keeping this material at rest on a surface covered with polyethylene film at temperatures not exceeding 20 ° C.

In the case of obtaining solid matrix powder and gel represented by metal and non-metal oxides, especially silica and alumina, and also from organic materials such as starch, the Schiff Reagent impregnation process comprises the steps of:

(a) Controlled dripping or wettability of the solid matrix by the homogeneous Schiff Reagent solution prepared by mixing a basic fuchsin (range around 0.02 to about 0.9%), a source of sulfite (range around 0.05 to about 1.8%) and a mineral acid (range about 0.07 to about 2.2%);

(b) Mixing the above system to a gel;

(c) Optionally to obtain dust, dry the material obtained in step b.

The components of the Schiff Reagent used were: a basic fuchsin, preferably p-rosaline; - a source of sulphite selected from sodium metabisulphite, sulfur dioxide, sulphorous acid, among others, with sodium metabisulphite being preferred; and a mineral acid selected from sulfuric acid, hydrochloric acid, among others, with sulfuric acid being preferred.

The term "wettability" presented in step (a) refers to the quality or state of being humidifiable, or the degree to which something can be moistened. Also the ability of any solid surface to get wet when in contact with

a liquid whose surface tension has been reduced so that the liquid spreads over the surface of the solid. Controlled drip refers to the addition of a volume sufficient for the solid matrix to be completely moistened without excess, allowing the formation of a kind of "gel", as well as facilitating the drying process.

In step (a) the preferred solid matrix is the sylic due to the results

promising use for detecting aldehydes and alcohols in both gel and powder form in different samples. This material also stands out due to Schiff Reagent stabilization and economy issues, presenting the same functionality as glass but being a more convenient option.

cockroach.

The reagents immobilized on solid matrices (tapes, powders, gels, etc.) thus obtained allow the colorimetric detection of aldehydes, applicable for the detection of alcohols, where previous oxidation to aldehydes is necessary by the addition of potassium permanganate solution. of oxalate solution to the sample.

In the Examples the starch and alumina immobilized Schiff Reagent is not

presented good results, as presented for the other solid matrices. It is believed that this process does not work well for these substrates, requiring adjustments. This reinforces the concept that the impregnation process is dependent on the type of solid matrix used.

Another aspect of the present invention relates to a method of

Analytical determination of samples based on the use of Schiff's Reagent prepared as mentioned in the method of stabilizing this reagent in various vehicles (liquids or solids) or obtaining this immobilized reagent in solid matrices described above.

In general, it is a qualitative colorimetric method for detection of alcohols and aldehydes. For alcohols, the method consists of diluting the sample and oxidizing the alcohols present in two steps using the first oxidizing agent, potassium permanganate (KMn04) in the presence of phosphoric acid (H3PO4), and the second stage an acidifying agent, oxalic acid (HOOCCOOH) in the presence of sulfuric acid (H2SO4). Aldehydes generated by the oxidation of alcohols are detected by the addition of Schiff's Reagent as a selective indicator for these 10 compounds, generating purple color when there is methanol present in the sample and remaining colorless in its absence. In the case of aldehydes, a prior dilution of the sample is performed and detection is performed directly by the addition of Schiff's Reagent, without prior oxidation, and a change in color to purple in the presence of aldehydes. In their absence there is no color change in the first few minutes, and then a rosette color is formed relative to the fuchsin used, especially p-rosaniline due to the decomposition of the Schiff Reagent upon dilution. The intensity of the purple color formed is proportional to the amount of aldehyde or alcohol, especially methanol present in the sample. In the dilution used in the samples it is possible to detect 20 concentrations from 0.01%. Using a controlled medium, the reagents used and the acid concentration in the sample, the method also allows to selectively detect the presence of methanol that is mixed with ethanol in liquid fuels and alcoholic beverages.

In one of its embodiments, the present invention relates to the application of the method to real samples, and it is possible to observe concentration ranges, according to the standards used, from 0 to 100% of methanol present in the sample, such as in ethyl alcohol pa, fuel alcohol, gasoline, beer and cachaça. Additionally, the method has also been applied to the detection of formaldehyde in commercial products such as detergent and shampoo.

It is noteworthy that the method of determination of aldehydes and / or alcohols

based on the use of stabilized Schiff's Reagent, as well as the elaboration and use of kits for this determination proposed here, are applied to any type of sample. Preferred samples for the intended application are those coming from commercial products, simply referred to by commercial samples, such as: - liquid fuels (gasoline, alcohol or ethanol obtained from different sources, dieseí and bicdiesel obtained from different sources) ; organic solvents; - carbonated or non-aerated alcoholic beverages obtained by fermentation or distillation processes 5 (cachaça, beer, wine, among others) and including energy drinks; - cosmetic and personal cleansing products, including hair care and cleaning products (shampoos, conditioners, etc.) and other perfumery, and - general and sanitizing cleaners. Sanitizing product means substances or preparations intended for sanitation, disinfection or household disinfection, in collective and / or public environments, in places of common use and in water treatment (http://www.anvisa.gov.br). / sanitizing, visited April 2012). Examples of sanitizing products include: detergents; bleaches; fabric softeners; antirust products; waxes; acid and alkaline descalers; clean furniture, plastics, 15 tires, glass; shoe or metal surface polishers; removers; soaps; saponaceous and others; disinfectants, such as general purpose, food industry, swimming pool, lactary, hospital (for fixed surfaces and semi-critical articles); water disinfectant for human consumption; deodorants, such as environmental deodorant, for sanitary appliances and others; sterilizers; algaecides and fungicides for swimming pools; insecticides; raticides; garden products; repellents among others.

In one of its embodiments, the present invention provides a kit for colorimetric determination of aldehydes and / or alcohols in different samples, comprising at least one stable solid or liquid Schiff Reagent of the present invention. For the determination of alcohols, especially methanol, this kit is also comprised of components selected from: an oxidizing agent, a reducing agent and an acidifying agent. As the preferred oxidizing agent is a sodium permanganate solution in the presence of phosphoric acid, the reducing agent is an oxalic acid solution and the acidifying agent is sulfuric acid. For simplicity, these components are referred to herein as “sample oxidation elements” and are necessary to promote prior oxidation of the sample alcohols to detectable aldehydes by interaction with the Schiff Reagent and to discover the solution, facilitating the visualization of the formed colors. by the addition of Schiff's Reagent, related to color change (violet for presence).

This determination kit is also characterized by further comprising:

(i) One or more complementary detection components, selected from: distilled or deionized water, known standard solutions of

according to the intended analysis, oxidation elements of the sample, in addition to Schiff Reagent in one of its forms proposed in the present invention;

(ii) One or more materials for sample preparation and analysis selected from: specific graduated container for conditioning the sample to be analyzed, volumetric collection devices and their accessories, test tubes or

suitable containers to perform the desired analyzes.

Standard solutions depend on the type of analysis desired, exemplified by mixtures of previously known proportions, such as ethanol / methanol / water, formaldehyde / water standards, among others, with concentrations ranging from 100 to 0% of the compound of interest ( methanol or formaldehyde). The exemplary volumetric collecting devices and their accessories refer to an automatic pipettor for collecting the sample and tips for the pipettor.

This analytical determination kit is also characterized by being supplemented with at least one of the following items:

(iii) safety features, such as gloves for handling reagents;

(iv) instruction and procedure manual;

(v) Portable case.

In any of the possible embodiments of the proposed kit, the liquid or solid phase stabilized Schiff Reagent of the present invention and the complementary components for detection (preferably distilled or deionized water, one or more standard solutions, oxidizing elements). (for the purpose of alcohol analysis), among others) are packaged in suitable containers or flasks, which are made of suitable structural materials, especially of polymeric or plastic materials, which do not interact with the liquid reagents and solutions used in the analysis. can be made available in presentations or models that make it easy to remove their contents in a controlled manner, for example: fixed or pre-set dispensing or dispensing bottles (manual or semi-automatic), with possibilities for refilling or use of refill. This dispenser dispenses the volume equivalent to that required for an analysis. In the case of water, preferably distilled or deionized, a fixed volume vial is used and adjusted to the required number of analyzes with its respective doser. For the cases of stabilized Schiff Reagent proposed here, it is further necessary that the used containers or vials (liquid reagent) or used packaging (solid reagent) allow the absence of free spaces or vacancy 10 as described above. Stabilized reagent solutions also have the possibility of being available for single dose use, with fixed or pre-established volumes according to the type of analysis to be performed. This controls the evolution of SO2 as well as reagent integrity and facilitates the operational steps of analysis by any user.

Still for single dosages, the vials or packages used

present possibilities of other variations of its constitution, which are allowed by the use of combinations of different materials already established by the technique for its preparation, for example, plasticized papers and metallized paper to obtain containers or boxes of different formats, 20 sachets, among others, aiming at economy and ease of use, disposal and final disposal after consumption of these packages in analysis methods.

The manual contains instructions on reagent use and specific information on reagent toxicity, handling precautions for reagents and materials, detailed steps for performing the analyzes, specimen specificities that must be taken into account for the applicability of the reagent methodology. analysis (for example, for carbonated beverages, sample degassing, etc.), ways to use stabilized Schiff's Reagent in various vehicles (liquids and solids), how to interpret results and how to discard waste analyze.

Also for any of the kit's constitution possibilities

proposed, the case is made of synthetic or natural material or combinations thereof, including plywood sheets. Examples of synthetic materials include rigid or soft polymers or plastics in general and combinations thereof, including metallic materials such as aluminum, stainless steel, alloys in general and combinations thereof. Natural materials are vegetable fibers, wood and its derivatives, such as paper among others, and combinations thereof.

The shape of the case allows variations such as square, rounded,

oval, oval, etc., or combinations thereof, provided that it allows adequate packaging of permanent or consumable items of the kit, for ease of handling and transportation. Thus, the kit has one or more doors, structural parts that fit, including drawers, forming a single set, with 10 one or more handles on the outside. The strap (s) have the characteristics of being: rigid, semi-rigid or flexible, movable or fixed and ergonomically shaped (provides the user with a more comfortable grip) or not arranged on the top and / or sides of the case.

Another aspect of the present invention is related to the development of a portable field analysis kit with all reagents and materials necessary for colorimetric determination of aldehydes and / or alcohols, especially methanol in commercial products (especially liquid fuels and alcoholic beverages). as well as formaldehyde analysis in cleaning and personal care products.The kit consists of the standards required for analysis according to the desired determination 20 (aldehydes and / or alcohols, mainly formaldehyde and methanol) and reagents with specific or at specific doses, including a liquid or solid stabilized Schiff Reagent of the present invention, so as to mix them only upon prior instructions, facilitating the manipulation of the reagents to analyze a particular sample.

In Example 5, a portable kit model was presented (Figures 1.a and 1.b),

applied to the analytical sample determination method based on the use of the stabilized Schiff Reagent of the present invention, especially applied to the methanol and formaldehyde determination of commercial samples mentioned above. This model is characterized in that it comprises the following parts: one or more covers (A), at least one of which is upper, for example a folding (A. 1) and / or front side (A.2), with lockable parts or with space for accommodation of the analytical components (B), selected from the complementary reagents and standards, which are attached to the dispensers or other element that facilitates the exit of the vial contents in a controlled manner, with the stabilized Schiff Reagent and tube rack or suitable containers for analysis (D) housed in fitting parts or in drawer (C) with separate spaces, while other miscellaneous compartments are for placing the other 5 constituent items, represented by a compartment for placing the pipettor (E), a compartment to accommodate one or more manuals (F), where (D) fits (C) and (C) fits through opening (A), forming a single piece or case containing at least one walking strap. In this example, the material used for making the case was plywood sheets.

The tests performed for the detection used aqueous solution of

Schiff Another method for detecting aldehydes and oxidized alcohols for aldehydes in the exemplified kit is impregnated materials, and any material impregnated by Schiff's Reagent may be used, by adapting the technique, such as paper. Using the paper, the automatic pipettor is used to collect the sample and then this volume is added to the paper, the color formed should be compared to the colorimetric pattern present in the instructions.

Analysis methods for the determination of aldehydes and / or alcohols presented for field analysis (any place of interest) of samples and employed in the kit are applied at temperatures in the range of about 15 to about 35 ° C, with preference being given to this. temperature range to avoid decomposition of reagents.

The analytical method for detecting methanol contamination comprises the following steps:

The. Dilute sample to be analyzed in water in the analysis vial;

B. Add to analysis vial oxidizing agent solution in medium

aqueous, with subsequent rest;

ç. Add to the test flask the aqueous solution of stirring acidifying agent and reducing agent until the obtained solution is discolored;

d. Add to the test flask the aqueous solution of the Schiff Reagent, with subsequent rest;

and. Compare staining obtained in solution with staining of known concentration solution analyzed by the methods described in steps (a) to (d).

In step a. Sample dilution is required only for methanol detection (eg reaching a concentration between 1 and 10% v / v, preferably around 5%. For aldehydes dilution is indicated but not it's essential.

In step b addition of oxidizing agent solution (one of the components of the sample oxidizing elements) is allowed at any concentration, for example 30 g / l where the oxidizing agent solution: sample solution ratio is preferably around 1: 2.5. In some cases the appropriate rest time should not be less than 10 minutes.

In step c the addition of acidifying agent and reducing agent solution (other components of the oxidizing elements of the sample) is allowed at any concentration, for example 50 g / l. The acidifying agent and reducing agent solution is preferably prepared by diluting oxalic acid in dilute sulfuric acid solution in water in any proportion, preferably using 50% each v / v ratio. In this case, the preferred ratio of acidifying agent and reducing agent: solution obtained from step b is around 1: 3.5.

In the examples, the Schiff Reagent solution used was prepared by diluting 3 reagents: p-rosaniline in water with concentrations of 0.02 - 0.9%, with about 0.29% w / w being preferred. , sodium bisulfite, with concentrations of 0.05 - 1.8%, being preferred around 0.61% w / w, and sulfuric acid, with concentrations of 0.07 - 2.2%, being preferred in around

0.78%.

In step d for the case of using the aqueous Schiff Reagent solution,

their addition is allowed at any ratio to the solution obtained in step c, preferably at a ratio of about 2.5: 4.5 for the exemplified cases. The immobilized reagents proposed in the present invention are also used.

The preparation of standard solutions containing ethanol and methanol allows

concentrations ranging from 100 to 0% methanol in ethanol and further dilution with water in any proportion, preferably reaching a 5% proportion of alcohols.

In the step and the qualitative determination of the presence or absence of the contaminant of the sample is completed, by observing the resultant staining, being a bluish-violet staining in the case of positive results in relation to the 5 samples contaminated by methanol and no color for the exempt samples. of methanol. Comparing the staining of the resulting sample solution with the staining of the standards gives approximate values for the contaminant concentration (quantitative determination - Example 6).

This analytical method was applied to real samples, mainly for gasoline, ethanol fuel, distilled / fermented beverages or carbonated alcoholic beverages, discussed below.

For gasoline analysis, a prior aqueous phase extraction procedure is required by adding water and further diluting the organic phase:

(a) place, for example, 20 ml of petrol in the graduated sample container;

b) Adjust the dispenser of the dilution solution bottle to 5mL and dispense this volume into the sample container containing the gasoline;

(c) Shake the mixture vigorously to ensure that the aqueous phase is extracted from the petrol and leave the flask to stand until the phases are separated;

d) Adjust the dispenser of the bottle containing the dilution solution to

4.5 mL and dispense this volume into a test tube;

e) Collect with a micropipette two aliquots of the aqueous phase (lower phase) extracted from the gasoline to be analyzed (0.50 mL) and add to the tube with the dilution solution, shaking to even the sample;

f) Follow the standard for methanol analysis.

For analysis of alcoholic beverages the same procedure as for rank alcohol described above is followed. Carbonated drinks should be degassed prior to performing step a preferably.

For aldehyde analysis, the methodology used is similar to that of methanol detection, except that sample dilution is optional and does not require the addition of oxidation elements. In a standard procedure, the following steps must be performed:

The. Dilute the sample to be analyzed in water if necessary;

B. Add to the solution obtained in step a, a stabilized Schiff Reagent as proposed in the present invention;

ç. Compare staining obtained in solution with staining of the standard solution used of known concentration subjected to steps a - b.

As an example, formalin analyzes were performed from the exemplified kit according to the following procedure:

(a) choose an appropriate environment for the procedure, with

temperature in the range 15 to 35 0C.

(b) Collect the volume of dilution solution dispensed into a test tube.

c) Collect with an micropipette an aliquot of the sample to be analyzed and add to the tube with the dilution solution, shaking to even the sample.

(d) Add one dose of Schiff's reagent to the sample and shake if aqueous reagent is used. The immobilized reagents proposed in the present invention are also used;

e) Observe the coloration formed and if necessary compare with a colorimetric pattern.

Aldehyde-containing standard solutions are prepared with concentrations ranging from 100 to 0% and further dilution with water, preferably reaching a concentration of 5% (aldehyde / water solutions).

If the sample is a partially hydrophobic emulsion, the hydrophilic components must be extracted in advance with water and then diluted to a concentration of 5%.

The aqueous Schiff Reagent solution is added in any amount, with a ratio of about 1: 1 (Schiff reagent solution: sample) being preferred.

The resulting stain for the test is bluish violet in case of positive results for aldehyde contaminated samples and no color for aldehyde free samples. Comparison of the resulting staining of the sample solution with the staining of the standards tested under the same conditions is used to quantify this contaminant.

Thus, the present invention further reports, for comparative purposes, the

quantitative analyzes of commercial products. For this, a UV-VIS spectrophotometer was used, providing the maximum absorbed wavelength, which is generally in the range of 586 to 592 nm. Analysis should be performed 45 minutes after the addition of Schiff Reagent within 55 minutes of the addition of Schiff Reagent. If the signal obtained is very strong, which varies according to Schiff Reagent activity, the samples should be diluted. The samples to be analyzed must undergo previous treatment, similar to that stipulated in the qualitative methods.

The experimental procedures involved are detailed in each of the following Examples, and it is important to note that the invention is not limited to the examples cited, but may be used in all described applications or in any other equivalent variations.

EXAMPLES: EXAMPLE 1: Preparation of Standards and Samples for Qualitative Analysis

The technique can accurately detect 0.01% interval variations

by volume of methanol up to approximately 2%. The amount of methanol in a sample can be observed from 0 to 100% by volume. To prepare the standards, methanol is mixed with methanol-free ethanol in determined volumes. From this solution is removed 5 mL and diluted to 100 mL with distilled water. To prepare a sample for analysis from an unknown sample, 5 mL of the sample to be analyzed is removed and diluted to 100 mL with distilled water. Solutions with larger or smaller volumes can be prepared by respecting the relationship between water and reagent volumes.

EXAMPLE 2: Qualitative Colorimetric Test for Methanol Analysis

A methanol-free blank was chosen. With this were prepared

standard solutions within a range of interest with defined concentrations. During the analysis a set temperature was maintained within a range of 15 to 35 ° C. Then 2.5 mL of each standard sample was measured and transferred to separate test tubes in increasing order of methanol volume. In parallel to this procedure, it was dispensed in a separate 5 2.5mL tube of the sample to be analyzed. In all samples 1 mL of potassium permanganate solution was added to each tube, and the contents of the tubes were stirred for 10 min. Then 1 mL of the oxalic acid solution was added to each tube, stirring until the solution was translucent. Then 2.5 ml of Schiff's Reagent was added to each tube, they were then shaken. The comparison between the sample and the standards should be made when the color in the samples is stable and accentuated, then determining the range in which the sample is located.

Depending on the amount of methanol in the samples the appearance of a blue-violet hue may be immediate after the addition of Schiff's Reagent, however 15 minutes should be allowed up to 10 min for a safe analysis. The maximum staining is observed in approximately 30 min, but the comparison between the sample and the standards can be done in a shorter time. The stronger the color shade, the greater the methanol concentration in the sample.

The pattern containing 0% methanol shall not be colored. It may show color in the first few minutes, but it should disappear during the analysis. If the pattern containing 0% methanol is colored, it may be that there is interference in the chosen white, methanol contamination or the reagents used are not in proper condition.

Five qualitative tests involving commercial samples were performed as an example. The first test was performed using 95% ethyl alcohol as white. Alcohol patterns were made using contaminations of 10, 25, 50, 75 and 100% methanol in ethyl alcohol, as observed in Figure 2.

The same procedure was performed for commercial samples, namely: Hydrated alcohol (standby alcohol), gasoline, beer and cachaça. The methanol-free samples were contaminated with methanol in different proportions and subjected to the qualitative test, as illustrated in Figures 3, 4, 5 and 6, respectively for hydrated alcohol, gasoline, beer and cachaça samples. The beer was previously degassed before sample preparation. The aqueous phase of gasoline was extracted with distilled water by a simple extraction process.

EXAMPLE 3: Qualitative colorimetric test for formaldehyde analysis

To assess the amount of formaldehyde in a commercial product simply dilute the sample by at least 5% with distilled water and 2 mL of this solution drip 2 mL of Schiff's Reagent. If the test is positive, a purple color should be observed in the solution after reagent addition. If the test is not positive, no purple color will be observed after the reagent has been added, but the colorless solution may turn rosy from p-rosaniline, although it may take some time to appear rosy.

The procedure was performed using commercially available real samples, such as shampoo and detergent. Both were free of formaldehyde and both were formaldehyde contaminated to evaluate the methodology. The result was positive and can be seen in Figures 7 and 8, respectively for shampoo and detergent samples.

EXAMPLE 4: Impregnation of Materials

Schiff reagent was used to impregnate solid materials in order to maintain its activity. Several solid materials were tested, including paper, silica gel, starch and alumina. These materials stabilize the reagent and maintain its activity for aldehyde detection.

EXAMPLE 4.1: Impregnating Paper with Schiff Reagent

The sheet of paper should be completely immersed in a solution of Schiff's Reagent. The entire area of the paper must come in contact with the reagent simultaneously, otherwise the reagent migrates through the non-immersed paper to decompose to p-rosaniline. To dry the paper, leave it on a surface covered with polyethylene film at temperatures not exceeding 20 ° C. Once dry, the paper has the same initial appearance, without the presence of color or stains, and should be stored between cooling polyethylene films in a closed container. Paper, if exposed to temperatures above 20 ° C, may have a slightly pink hue, which does not impair its ability to detect aldehydes. If exposed to high temperatures the paper darkens, losing its activity. If not kept cool, the paper darkens to a dark tinge, losing its activity. To improve the performance of analysis using paper, it can be stored under surfaces so as not to leave vacant space avoiding paper SO2 loss. For example, one can use contact paper to store paper between them and thus maintain their activity.

Impregnated paper can detect aldehydes in concentrations below 1% by only adding a drop of the analyte to its surface. Aldehydes generate a violet color on the paper. In paper the color intensity is also proportional to the aldehyde concentration in the sample. Addition of alcohol or water does not generate color and degradation of the reagent to p-rosaniline may occur, in which case a pink coloration is observed, quite different from the violet tone generated by the Schiff Reagent.

Impregnated paper is used to detect alcohols. To do this, simply perform the previous oxidation to aldehydes with the potassium permanganate solution for 10 min, followed by the addition of the oxalate solution as described above. Then, after the solution turns colorless, it drips onto the paper. In case of contamination with methanol there will be a violet tone generated by the Schiff Reagent.

EXAMPLE 4.2: Impregnation of Silica with Schiff Reagent

Silica stabilizes Schiff's Reagent, which remains colorless and active against aldehydes. Through impregnation, two different forms of the impregnated silica can be obtained. First spread the silica on an inert surface and uniformly add the Schiff Reagent onto the silica. To obtain a gel, add the still damp silica, placing it in a closed container and keeping it cool. To obtain a powder, after dripping Schiff's Reagent onto the silica, it is spread over the surface and allowed to dry at temperatures close to 20 ° C. Silica can also be stored under surfaces to minimize vacant space, avoiding loss of SO2 as described for paper.

The test using silica is based on the dispersion of the powder or gel in the solution containing the analyte. In solution, the silica releases the reagent generating purple color in the presence of aldehyde, or red or pink color in solution without aldehyde. Impregnated silica can be used to detect alcohols by prior oxidation to aldehydes as described for paper.

EXAMPLE 4.3: Impregnation of Alumina with Schiff Reagent

Schiff's reagent was immobilized on alumina according to

procedure described for silica (Example 4.2).

EXAMPLE 4.4: Starch Impregnation with Schiff Reagent

Schiff's reagent was immobilized on starch according to the procedure described for silica (Example 4.2).

EXAMPLE 5: Kit for field analysis using methods for the determination especially of methanol and formaldehyde in commercial products.

The exemplary kit model (Figures 1.a and 1.b) for the determination especially of methanol and formaldehyde in commercial samples consists of four main parts:

(i) Detection reagents stored in flasks containing

dosers and in adjusted doses;

(ii) Materials for sample preparation;

(ii) Instruction manual and procedures;

(iv) Drawer and compartments for conditioning items.

The kit is made according to the amount of analysis in demand, keeping

standard materials and solutions included.

This exemplified kit contains:

(a) A fixed-volume vial containing potassium permanganate solution, with volume and concentration adjusted for the number of analyzes.

defendants and their respective doser;

(b) a fixed-volume vial containing the oxalic acid solution, with volume and concentration adjusted for the required number of analyzes, and their respective dispenser;

(c) One or more fixed volume vials containing the standard solution for comparative analysis. In the case of methanol, with volume adjusted to the required number of analyzes and desired concentration, being suggested 1%, with its respective doser;

(d) A fixed volume vial containing dilution water adjusted to the number of analyzes required with its respective dispenser;

(e) Vials containing fixed volumes of the Schiff Reagent solution (stabilized in aqueous solution), the number being determined by the amount of analysis required and the volume and concentration equivalent to that required for one analysis (single dose). This reagent immobilized on different

Solid matrices (eg tapes of cellulosic or paper material, metal oxides and polymers in gel or powder form - silica, alumina and starch).

The materials included in the kit are:

(a) safety equipment, eg gloves for handling reagents;

(b) test tubes to perform the analyzes;

(c) support for test tubes;

(d) automatic pipettor to collect the sample;

(e) pipettor tips;

(f) 50 mL graduated container specific for conditioning the sample;

(g) operating manual of the kit for analysis;

(h) Impregnated materials may also be included in the kit as desired.

This kit is divided into permanent parts and consumable parts. The dosers, the pipettor, the test tubes, the test tube holder and the

Sample containers are permanent, so they are included in the main kit only. Reagents, standard and dilution solutions as well as gloves and tips are considered consumable, and are also included in the main kit as well as may be ordered on demand (replacement items).

Another way for detecting aldehydes and oxidized alcohols for aldehydes in

exemplified kit, are the impregnated materials, and any material impregnated by the Schiff Reagent may be used, by adapting the technique, such as paper. Using the paper, the automatic pipettor is used to collect the sample and then this volume is added to the paper, the color formed should be compared to the colorimetric pattern present in the instructions.

EXAMPLE 6: Colorimetric quantitative test for methanol analysis

A fifteen point curve was constructed, with methanol concentration ranging from 0.01 to 0.2%. The linear fit for the obtained curve provided the value of r2 = 0.9681. The calibration curve can be used, but with a considerable error associated. This analysis is limited by the analysis time relative to the adduct stability time, which revolves around a 10 min range, so that it is not possible to plot many points to construct a line without having an error associated with concentration. The release of gases also greatly influences the analysis, so sample to cuvette transfers should be done smoothly. The calibration curve must be made for each sample and analysis. The matrix in which the analyte is located may change and interfere with absorbance. Depending on its storage time, Schiff's Reagent may vary the concentrations of some of its components, so that its reactivity with the formaldehyde formed from methanol may also change, in which case the absorbance values will be different, so would need a prior calibration curve each time this analysis is performed.

The standard addition method was also applied for ethanol, ethanol, gasoline, beer and cachaça samples, so that five standard samples were made for ethanol, alcohol and cachaça samples and four standard samples for samples. of gasoline and beer. The r2 obtained for the 25 samples of ethanol, ethanol, gasoline, beer and cachaça were 0.98625, 0.95842 respectively. 0.909038, 0.98961 and 0.98103. Thus, it was observed that good results can be obtained, as in the case of gasoline, but the excess of steps, the volatility of the reagents, the sensitivity of the reagents, the presence of parallel reactions and the formation of more than one species. the system reaches a steady state. Thus, the system only allows reliable results if it is always done by comparing the sample results with the result of a known standard solution.

Claims (58)

1. Method of stabilizing the Schiff reagent in various liquid or solid vehicles, comprising the steps of: (a) preparing a homogeneous solution of Schiff's reagent by mass mixing of its constituents represented by: a basic fuchsin (range) about 0.02 to about 0.9%), a source of sulfite (range from about 0.05 to about 1.8%) and a mineral acid (range from about 0.07 to about 2.2%); b) Pack the solution in appropriate packaging or containers, without vacancy spaces; or c) Putting the solution obtained in step a in contact with matrices or solid substrates for a period and then drying them. SCHIFF REAGENT STABILIZATION METHOD according to claim 1, characterized in that the basic fuchsin is preferably rosaline. SCHIFF REAGENT STABILIZATION METHOD according to claim 1, characterized in that the sulfite source is selected from sodium metabisulphite, sulfur dioxide, sulphorous acid and other sulfur compounds. SCHIFF REAGENT STABILIZATION METHOD according to claim 1 or 3, characterized in that the source of sulfite is preferably sodium metabisulfite. SCHIFF REAGENT STABILIZATION METHOD according to claim 1, characterized in that the mineral acid is selected from sulfuric acid, hydrochloric acid and other mineral acids. SCHIFF REAGENT STABILIZATION METHOD according to claim 1 or 5, characterized in that the mineral acid is preferably sulfuric acid. SCHIFF REAGENT STABILIZATION METHOD according to claim 1, characterized in that the liquid phase stabilized reagent comprises an aqueous solution. SCHIFF REAGENT STABILIZATION METHOD according to claim 1 or 7, characterized in that the Schiff Reagent solution is filled into containers or vials with fixed or pre-filled dispensers or dispensers (manual or semi-automatic or automatic). -stablished, allowing direct or refill or refill use, including for single dose use. SCHIFF REAGENT STABILIZATION METHOD according to claim 1, characterized in that the solid matrices used are selected from cellulosic material or paper, metal and non-metal oxides, polymers or any other solid substrate that can support the Schiff Reagent. without breaking it down. SCHIFF REAGENT STABILIZATION METHOD according to claim 1 (step c) or 9, characterized in that drying is carried out at temperatures preferably below 20 ° C. SCHIFF REAGENT STABILIZATION METHOD according to claim 1 (steps aec), 9 or 10, characterized in that the obtained solid matrix impregnated Schiff reagent is packaged so as not to have vacancy spaces between the package and its packaging. content. SOLID MATERIALS IMMOBILIZED SCHIFF REAGENT characterized in that it comprises the Schiff Reagent prepared according to claims 1 (steps a and c), 9 or 10. IMMOBILIZED SCHIFF REAGENT according to claim 12, characterized in that the solid phase stabilized reagent comprises different presentations, selected from: tapes, plates, gels, powders or other forms resulting from impregnation in solid matrices or substrates. IMMOBILIZED SCHIFF REAGENT according to claim 12 or 13, characterized in that the reagent provided in the form of tapes is of cellulosic material or paper. IMMOBILIZED SCHIFF REAGENT according to claim 12 or 13, characterized in that the reagent provided in the form of gels and powders is silica or silicon oxide, to be used pure or immobilized on solid substrates. 16. Schiff reagent impregnation process in cellulosic material comprising the steps of: A) Fully immersing the appropriately sized cellulosic material in a homogeneous solution of the Schiff Reagent prepared by mixing: - a basic fucine in a band around 0.02 to about 0.9% as defined in claim 2; a source of sulphite in a range around 0.05 to about 1.8% as defined in claim 3 or 4; and a mineral acid in a range from about 0.07 to about 2.2% as defined in claim 5 or 6; B) Remove the cellulosic material from the previous system and promote its drying. SCHIFF REAGENT IMPREGNATION PROCESS according to claim 16, characterized in that the cellulosic material is paper or any of its variations containing cellulose obtained from different plant sources, including industrial waste or scrap. 18. SCHIFF REAGENT IMPREGNATION PROCESS in solid matrices, comprising the steps of: (a) Controlled dripping or wettability of the solid matrix by the homogeneous solution of Schiff Reagent, prepared by mixing: - a basic fuchsin in a strip in about 0.02 to about 0.9% as defined in claim 2; a source of sulphite in a range around 0.05 to about 1.8% as defined in claim 3 or 4; and a mineral acid in a range from about 0.07 to about 2.2% as defined in claim 5 or 6; (b) Vigorously mixing the anterior system to a gel; (c) Optionally to obtain dust, dry the material obtained in step b. SCHIFF REAGENT IMPREGNATION PROCESS according to claim 18, characterized in that the solid matrices used are selected from silica, alumina and starch. SCHIFF REAGENT IMPREGNATION PROCESS according to one of Claims 16 to 19, characterized in that the drying is carried out at temperatures preferably below 20 ° C. A method for the determination of aldehydes and / or alcohols by at least one of the stabilized Schiff Reagents prepared according to any one of claims 1 to 20 and different types of samples. DETERMINATION METHOD according to claim 21, characterized in that the samples are samples of commercial products. DETERMINATION METHOD according to claim 21 or 22, characterized in that the samples are selected from: - liquid fuels, - organic solvents, - carbonated or non-carbonated alcoholic beverages, - cosmetic and personal care products, including cleaning and cleaning agents. hair care, - general cleaning and sanitizing products. DETERMINATION METHOD according to claim 23, characterized in that the liquid fuel samples are selected from gasoline, alcohol or ethanol obtained from different sources and diesei or biodiesel obtained from different sources. DETERMINATION METHOD according to Claim 23, characterized in that samples of carbonated or non-carbonated alcoholic beverages are selected from cachaça, beer and other distilled or fermented beverages, and energy drinks. DETERMINATION METHOD according to Claim 23, characterized in that the samples of cosmetic and personal care products are selected from shampoos, conditioners, deodorants and other perfumery products. DETERMINATION METHOD according to Claim 23, characterized in that the samples of general and sanitizing cleaners are selected from the group of detergents, bleaches, fabric softeners, antifrust products, waxes, acid and alkaline descalers, mobile cleaners, plastic cleaners, tire cleaners, window cleaners, shoe or metal surface polishers, removers, soaps, soaps and derivatives, general purpose disinfectants, water disinfectant, deodorants, sterilizers, algaecides and pool fungicides, insecticides, pesticides, garden products and repellents. Method of determining according to one of Claims 21 to 27, characterized in that it is carried out in the field or at the place of interest. DETERMINATION METHOD according to claim 28, characterized in that the field embodiment comprises temperatures in the range from 15 to 35 ° C. DETERMINATION METHOD according to claim 28 or 29, characterized in that it uses standard solutions selected from: - methanol / ethanol / water, with concentrations ranging from 100% to 0% methanol in ethanol and further dilution with water. (methanol detection), - formaldehyde / water, with concentrations ranging from 100 to 0% formaldehyde in water (formaldehyde detection), or other standard solutions according to the desired analysis. DETERMINATION METHOD according to one of Claims 28 to 30, characterized in that it is used for the qualitative and quantitative colorimetric determination of aldehydes or alcohols, especially formaldehyde and methanol, by comparing the color results presented by the solutions. standards used with the same treatment as the samples analyzed. DETERMINATION METHOD according to one of Claims 28 to 31, characterized in that the detection of oxidized aldehydes and alcohols to aldehydes is carried out by prior oxidation of the alcohols present in the sample to aldehydes by the addition of oxidizing elements of sample, comprising the addition of an oxidizing agent, a reducing agent and an acidifying agent. DETERMINATION METHOD according to claim 32, characterized in that the oxidizing agent is a solution of sodium permanganate in the presence of phosphoric acid. DETERMINATION METHOD according to claim 32, characterized in that the reducing agent is an oxalic acid solution. DETERMINATION METHOD according to claim 32, characterized in that the acidifying agent is sulfuric acid. DETERMINATION METHOD according to one of Claims 21, 24, 28 to 35, characterized by the prior extraction of water-soluble constituents when the selected sample is gasoline. DETERMINATION METHOD according to one of Claims 21, 25, 28 to 35, characterized by prior degassing of the sample when the selected sample is a carbonated alcoholic beverage. DETERMINATION METHOD according to claim 21, characterized in that it detects methanol contamination, comprising the following steps: a. Dilute sample to be analyzed in water; B. Add to the diluted solution one volume of oxidizing agent solution in aqueous medium with subsequent rest; ç. Add to the solution obtained in step b. a volume of stirring and reducing agent until the solution obtained is discolored; d. Add to the solution obtained in step c. a stabilized Schiff Reagent according to any one of claims 1 to 20; and. Compare staining obtained in solution with the staining of the standard solution used of known concentration subjected to steps a - d. DETERMINATION METHOD according to claim 38, characterized in that it detects methanol contamination in product samples as defined in one of claims 22 to 27. DETERMINATION METHOD according to claim 21, characterized in that it detects contamination by aldehydes, comprising the following steps: a. Dilute the sample to be analyzed in water if necessary; B. Add to the solution obtained in step a. a stabilized Schiff Reagent according to any one of claims 1 to 20, with subsequent rest; ç. Compare staining obtained in solution with the staining of the standard solution used of known concentration subjected to steps a - b. DETERMINATION METHOD according to claim 40, characterized in that it detects formaldehyde contamination in product samples as defined in one of claims 22 to 27. DETERMINATION METHOD according to claim 40 or 41, characterized in that it pre-extracts the hydrophilic components in water in case the sample is a partially hydrophobic emulsion. KIT FOR COLORIMETRIC DETERMINATION OF ALCOHOLS AND / OR ALDEIDS IN DIFFERENT SAMPLES based on the use of the Schiff Reagent characterized in that it comprises the use of at least one stable liquid or solid Schiff Reagent prepared according to one of claims 1 to 20. . DETERMINATION KIT according to claim 43, further comprising: (i) One or more complementary detection components, selected from: distilled or deionized water, known standard solutions according to the desired analysis, sample oxidation in case of determination of alcohols; (ii) One or more materials for sample preparation and analysis selected from: specific graduated container for conditioning the sample to be analyzed, volumetric collection devices and their accessories, test tubes or containers suitable for performing the intended analysis. DETERMINATION KIT according to claim 43 or 44, further comprising at least one of the following: (i) safety equipment; (ii) Instruction manual and procedures; (iii) portable case. DETERMINATION KIT according to claim 44, characterized in that the oxidizing elements of the sample comprise an oxidizing agent, a reducing agent and an acidifying agent. DETERMINATION KIT according to claim 46, characterized in that the oxidizing agent is a solution of sodium permanganate in the presence of phosphoric acid. DETERMINATION KIT according to claim 46, characterized in that the reducing agent is an oxalic acid solution. DETERMINATION KIT according to claim 46, characterized in that the acidifying agent is sulfuric acid. DETERMINATION KIT according to claim 44, characterized in that the standard solutions are selected from: - methanol / ethanol / water, with concentrations ranging from 100% to 0% methanol in ethanol and further dilution with water (detection - formaldehyde / water, with concentrations ranging from 100% to 0% formaldehyde in water (formaldehyde detection), or other standard solutions according to the desired analysis. 51. The method for determining according to claim 44, characterized in that the volumetric collecting devices and their accessories are an automatic pipettor for collecting the sample and tips for the pipettor. DETERMINATION KIT according to claim 45, characterized in that the case has: - variations in the materials for its manufacture and shape, aiming at the proper packaging of the permanent or consumable items of the kit and ease of handling and transportation, - and / or have one or more doors, and / or engaging structural parts, including drawers, forming a single assembly with one or more handles on its exterior. DETERMINATION KIT according to one of Claims 43 to 52, characterized in that the liquid phase Schiff Reagent and the complementary detection components (water, standard solutions and oxidizing elements of the sample) are comprised of: containers or packaging or bottles with presentation forms or models which allow the ease of withdrawal in a controlled manner, selected from: bottles with dispensers or dispensers (manual or semi-automatic or automatic) of fixed or pre-established volumes, with possibilities of refill or refill use. DETERMINATION KIT according to claim 53, characterized in that the Schiff's Reagent used in the liquid phase or aqueous solution is comprised of single dose presentation containers or packaging. DETERMINATION KIT according to one of Claims 43 to 54, characterized in that it comprises the following parts: one or more covers (A), at least one of which is upper, for example a folding (A.1) and / or front sides (A.2), with seatable parts or with space for the accommodation of the analytical components (B), selected from the complementary reagents and standards, which are attached to the dispensers or other element that facilitates the exit of the contents of the Controlled vial, with stabilized Schiff Reagent and tube rack or suitable test containers (D) housed in lockable parts or drawer (C) with separate spaces, while other miscellaneous compartments are for holding the vials. other constituent items, represented by a compartment for placing the pipettor (E), a compartment to accommodate one or more manuals (F), where (D) The strap at (C) and (C) fits into opening (A), forming a single piece or case, containing at least one locomotion strap. Use of the stabilized Schiff Reagent prepared according to one of Claims 1 to 20, characterized in that it is used in a colorimetric determination method for aldehydes and alcohols or in a determination kit for such compounds. Use of Schiff Reagent according to Claim 56, characterized in that it is used in a method or kit for the determination of formaldehyde and methanol in samples of commercial products in the field or at the place of interest. Use of the stabilized Schiff Reagent prepared according to any one of claims 1 to 20, characterized in that it is used in a method of aldehyde colorimetric determination or as dyes in biological systems or in the verification of contaminants in the atmosphere.