CN106018620A - Method for quickly and accurately detecting formaldehyde content and methanol content in cosmetics - Google Patents

Abstract

The invention discloses a method for quickly and accurately detecting the content of formaldehyde and methanol in cosmetics; utilizing the characteristic that formaldehyde can react with sodium borohydride to form methanol under alkaline conditions, a method is established by detecting the content of methanol in the gas phase under equilibrium conditions. A detection technology for simultaneous detection of formaldehyde and methanol content in cosmetics. And by adding internal standard substance to eliminate the error introduced in the detection process, the sensitivity of detection is improved, and the accurate and rapid detection of formaldehyde and methanol is realized. The method is rapid, objective and accurate, and easy to operate, and is suitable for online control of formaldehyde and methanol in cosmetics and detection of formaldehyde and methanol in commercially available cosmetics. It effectively overcomes the disadvantages of the current detection methods for methanol and formaldehyde in cosmetics.

Description

A method for fast and accurate detection of formaldehyde and methanol content in cosmetics

technical field

The invention relates to the technical field of cosmetic detection, in particular to a method for rapidly and accurately detecting the content of formaldehyde and methanol in cosmetics.

Background technique

Formaldehyde and methanol are commonly used additives in the cosmetics industry, and are widely used in skin care products, nail polish, soap, shampoo, body wash and other products. Formaldehyde is often used as a preservative for cosmetics because of its good hydrophilicity, high sterilization rate, low price, and not being affected by the pH in the system. Methanol in cosmetics is mainly used as a solvent. However, because formaldehyde is a volatile organic compound, it is toxic to the eyes, respiratory, nervous and endocrine systems, and has carcinogenic and mutagenic genetic effects. Methanol has an obvious accumulation effect on the human body. Methanol and its metabolites formaldehyde and formic acid can damage the central nervous system of the human body. In extreme cases, it can cause insomnia, coma or even death. Long-term exposure to trace amounts of methanol will cause great harm to the human body. The content of formaldehyde and methanol in cosmetics has been strictly limited by many countries and institutions. For example, the 2007 edition of my country's "Hygienic Standards for Cosmetics" stipulates that formaldehyde is a restricted substance, and the mass ratio content in oral hygiene products must not exceed 1g/kg, and the mass ratio content in other products must not exceed 2g/kg (calculated as free formaldehyde). It shall not be detected in cosmetics. In cosmetics containing formaldehyde or formaldehyde-releasing agents, when the mass ratio of formaldehyde exceeds 500 μg/g (calculated as free formaldehyde), the product label must be marked "contains formaldehyde". Moreover, it is stipulated that the methanol content shall not exceed 0.2% (2000mg/kg). Therefore, the ability to quickly and accurately detect the content of formaldehyde and methanol in cosmetics plays an important role in the online monitoring of the quality of cosmetic products and the safety of marketed products, especially for the quality and safety of cosmetics that are directly in contact with children.

Formaldehyde is unstable in air and other gas-phase substrates at a temperature of 150°C. It will quickly self-polymerize into dimers, trimers, or combine with moisture in the air to form methylene glycol; but these reactions occur randomly and do not react Completely, so it is not feasible to establish a quantitative detection method for formaldehyde by detecting formaldehyde dimers, trimers or methylene glycol and other substances. In view of this, most of the detection methods of formaldehyde adopt derivatization reaction. At present, the commonly used formaldehyde detection method in the cosmetics industry is to use formaldehyde, acetylacetone and ammonium to form a yellow compound diacetyl dihydrolutidine, and then perform spectrophotometric determination. The biggest problem with this method is that samples containing color (such as nail polish) cannot be deducted by a simple blank sample, so it is not suitable for detecting cosmetics containing color. Therefore, most of the detection methods for formaldehyde use high performance liquid chromatography and gas chromatography based on derivatization reactions.

At present, the methods for the determination of methanol in cosmetics have been reported at home and abroad mainly include gas chromatography, high performance liquid chromatography, colorimetry and gas phase-Fourier transform infrared spectroscopy. Due to the complex composition of samples in cosmetics, only separation-based high-performance liquid chromatography and gas chromatography can accurately detect the methanol content in cosmetics. Like the detection of formaldehyde in cosmetics, methanol detection must also undergo sample pretreatment, such as filtration, extraction or derivatization. Obviously, these sample pretreatment procedures are complicated and time-consuming when detecting the content of formaldehyde and methanol in cosmetics, making these methods not only inefficient but also introducing large experimental errors.

At present, a method for detecting formaldehyde in paper products by headspace gas chromatography has been developed. This method is based on the fact that formaldehyde can react with sodium borohydride to generate methanol under alkaline conditions, and by analyzing the methanol content in the gas phase under equilibrium conditions Detection To establish an indirect detection technology for formaldehyde content in paper products. However, because the content of methanol in cosmetics is too high, it will cause great interference to the detection of methanol generated by the conversion of formaldehyde, so the formaldehyde content in cosmetics cannot be accurately detected. Therefore, it is very important to be able to establish a new method for quickly and accurately detecting the content of formaldehyde and methanol in cosmetics.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art, and provide a method for quickly and accurately detecting the content of formaldehyde and methanol in cosmetics; it has the advantages of fast detection speed, accurate results, and easy operation. The disadvantages of the current methods for detecting the content of formaldehyde and methanol in cosmetics are overcome.

The present invention realizes through following technical scheme:

A method for quickly and accurately detecting the content of formaldehyde and methanol in cosmetics, using the characteristics that formaldehyde can react with sodium borohydride to form methanol under alkaline conditions, and establishing a simultaneous detection method by detecting the content of methanol in the gas phase under equilibrium conditions Determination method of formaldehyde and methanol content in cosmetics. And by adding internal standard substance to eliminate the error introduced in the detection process, the accurate and rapid detection of formaldehyde and methanol is realized.

Including the following steps:

Step (1) Make-up sample preparation process:

Add the sample to potassium carbonate solution, then shake and extract in a constant temperature water bath;

Step (2) sample detection:

Get the sample extract after step (1) processing in different headspace vials, then after adding the internal standard solution and sodium borohydride-internal standard solution of the same concentration volume in the headspace vials, the gland is sealed; After equilibrating in the headspace sampler, it is detected by gas chromatography, and the gas phase signal values of methanol and internal standard are recorded;

Step (3) methanol standard curve:

Prepare methanol solutions with different concentrations, add them to different headspace bottles in turn, add volatile internal standard substance and potassium carbonate solution at the same time, and then press the cap to seal; , draw the relationship between the gas phase signal ratio and the concentration of methanol and the internal standard;

Step (4) result analysis:

The content of formaldehyde and methanol in cosmetics is obtained by the following formula:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 800</span>}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 750</span>}<span\; class="notranslate">\; \&times;</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

w: mass of sample added, g;

R ₀ : add methanol and internal standard signal ratio in the sample headspace bottle of volatile internal standard solution;

R ₁ : methanol and internal standard signal ratio detected in the sample headspace vial of sodium borohydride-volatile internal standard solution;

s: the gas phase signal ratio of methanol and the internal standard and the slope of the concentration standard curve;

a: The gas phase signal ratio of methanol and the internal standard and the intercept of the concentration standard curve;

In the above step (1), the shaking temperature of the constant temperature water bath is 40° C., and the extraction time is greater than 60 minutes.

In the above step (2), the internal standard is a volatile substance, and the internal standard and sodium borohydride-internal standard are dissolved in potassium carbonate solution.

The potassium carbonate solution concentration of dissolving internal standard substance and sodium borohydride in the above-mentioned step (2) is identical with the potassium carbonate concentration in the step (1).

In the above step (2), the headspace equilibrium temperature is 105°C, the equilibrium time is 45 minutes, the vibration condition is set to strong oscillation, the pressurization time of the headspace bottle is 10s, the filling time of the quantitative loop is 15s, and the transfer time to the GC is 20s;

The operating conditions for gas chromatography detection are: hydrogen ion flame detector, carrier gas is nitrogen, flow rate 3.8mL/min, pressure 30psi, inlet temperature 250°C, capillary column temperature 80°C, splitless, detection time 2min.

In above-mentioned step (3), add potassium carbonate concentration and volume and step (2) potassium carbonate volume and concentration are identical in the headspace bottle.

The concentration and volume of the internal standard substance added in the above step (3) are the same as the internal standard substance added in the step (2).

Compared with the prior art, the present invention has the following advantages and effects:

The invention utilizes that formaldehyde can react with sodium borohydride to generate methanol under alkaline conditions and adds an internal standard substance, and effectively improves detection accuracy by optimizing extraction conditions and reaction conditions.

The detection method of the invention is easy to operate and has high precision, and is suitable for on-line control of formaldehyde and methanol in cosmetics and detection of formaldehyde and methanol in commercially available cosmetics.

The method not only has simple and convenient technical means, but also overcomes the common disadvantages of the current methods for detecting formaldehyde and methanol in cosmetics.

Description of drawings

Figure 1 is the influence of potassium carbonate concentration on the detection of methanol

Fig. 2 is the sample chromatogram of adding internal standard isopropanol

Figure 3 is the error comparison between the internal standard method and the traditional method for detecting formaldehyde content

detailed description

The present invention will be further specifically described in detail below with reference to FIGS. 1 to 3 in conjunction with specific embodiments.

Instruments and equipment used in the present invention: HP-7694 type automatic headspace sampler, Agilent A7890 type gas chromatograph (hydrogen ion flame detector, DB-5 type capillary chromatographic column), headspace bottle (21.6ml), white special Teflon/white silicone septa (with iron cap).

Reagents used in the present invention: methanol (analytically pure), isopropanol (analytical pure), formaldehyde (analytical pure), sodium borohydride, potassium carbonate.

Example 1

Determination of the concentration of the extract of the present invention

1. Sample preparation

Accurately weigh 0.3g of cosmetic samples (emulsion) into conical flasks, then add 25mL of potassium carbonate solutions of different concentrations (concentration ranges from 100g/L to 824g/L), and then shake and extract in a water bath at 40°C for 60min.

Pipette 5mL of the above extracts into different headspace vials, and then use a capper to seal the caps, and detect and analyze them in headspace gas chromatography.

2. Detection method

Headspace sampler conditions: equilibration temperature is 105°C, equilibration time is 45min, vibration condition is set to strong oscillation, sample vial pressurization time is 10s, quantitative loop filling time is 15s, transfer to GC time is 20s.

Gas chromatography operating conditions: hydrogen ion flame detector (FID), carrier gas is nitrogen, flow rate 3.8mL/min, pressure 30psi, inlet temperature 250°C, capillary column temperature 80°C, splitless, detection time 2min.

In the 2007 edition of my country's "Hygienic Standards for Cosmetics", the formaldehyde extract is a 125g/L sodium sulfate solution. The present invention selects potassium carbonate solution as the extract of formaldehyde in cosmetics, because the potassium carbonate solution not only provides an alkaline environment for the formaldehyde reaction, but also greatly improves the detection sensitivity due to the salting-out effect. It can be seen from Figure 1 that the signal value of methanol increases exponentially with the increase of potassium carbonate concentration. However, considering that a high concentration of potassium carbonate solution will reduce the extraction efficiency of formaldehyde and methanol hydrophilic substances in cosmetics, and the pH of 600g/L potassium carbonate solution ≈ 12.4 is enough to provide an alkaline environment for formaldehyde reaction. Therefore, the concentration of the cosmetic extract is selected as 600g/L potassium carbonate solution.

Example 2

Choice of internal standard

Sample preparation and testing

Accurately weigh 0.3g of the sample (nail polish) into a conical flask, then add 25mL of 600g/L potassium carbonate solution, and then shake and extract in a water bath at 40°C for 60min.

Pipette 5 mL of the above extract into a headspace bottle, and add 0.1 mL of isopropanol-potassium carbonate solution (concentration of isopropanol: 100 mg/L, concentration of potassium carbonate: 600 g/L). Then use a capper to seal the cap, and perform detection and analysis in the headspace gas chromatography according to the detection method of Implementation 1, and obtain the sample detection chromatogram in Fig. 2 . According to Figure 2, we can see that methanol and isopropanol signals can be well separated, which provides sufficient and necessary conditions for the establishment of the internal standard method.

Example 3

Effect of adding internal standard on detection sensitivity

1. Sample preparation

Accurately weigh 0.3g of the sample (nail polish) into a conical flask, then add 25mL of 600g/L potassium carbonate solution, and then shake and extract in a water bath at 40°C for 60min. Do four parallel samples at the same time.

Pipette 5mL of the above sample extracts into different headspace vials, add 0.1mL of isopropanol-potassium carbonate solution (propanol concentration: 100mg/L, potassium carbonate concentration: 600g/L) and hydroboration Sodium-isopropanol-potassium carbonate solution (sodium borohydride concentration: 5g/L, propanol concentration: 100mg/L, potassium carbonate concentration: 600g/L). Then use a capper to seal the cap, and perform detection and analysis in headspace gas chromatography according to the detection method in Implementation 1. The error comparison analysis of the two detection methods in Table 1 is obtained. From Table 1, we can see that the detection error (RSD) obtained by the traditional method for detecting this sample (formaldehyde content=45mg/kg) is very large ~ 27%. The addition of internal standard can significantly reduce the detection error by the internal standard method, and the RSD is reduced to 3.6%. Therefore, the method of the present invention can effectively reduce detection errors and improve detection sensitivity by adding an internal standard.

Table 1 Error comparison of two detection methods

A ₁ : signal of methanol before reaction; A _s1 : signal of isopropanol added before reaction;

A ₂ : signal of methanol after reaction; A _s2 : signal of isopropanol added after reaction;

R ₂ : methanol and internal standard signal ratio before reaction; R ₁ : reaction methanol and internal standard signal ratio;

Example 4

method accuracy

The accuracy of the method of the present invention is verified by the recovery rate. Accurately weigh 0.3g of the cleansing oil sample into a conical flask, add 50μL of methanol and formaldehyde solutions of different concentrations, then add 25mL of 600g/L potassium carbonate solution, and shake and extract in a water bath at 40°C for 60min.

Pipette 5mL of the above sample extracts into different headspace vials, add 0.1mL of isopropanol-potassium carbonate solution (propanol concentration: 100mg/L, potassium carbonate concentration: 600g/L) and hydroboration Sodium-isopropanol-potassium carbonate solution (sodium borohydride concentration: 5g/L, propanol concentration: 100mg/L, potassium carbonate concentration: 600g/L). Then use a capper to seal the cap, and perform detection and analysis in headspace gas chromatography according to the detection method in Implementation 1. According to the formula (1) and (2), the content of methanol and formaldehyde detected is calculated, and the recoveries of methanol and formaldehyde are obtained respectively, which are tables (2) and (3). According to table (2) and (3) methanol-formaldehyde recovery table can find out, the methanol-formaldehyde recovery rate is 94-103%, illustrates that this invention is applicable to the detection of methanol and formaldehyde in cosmetics.

Table 2 methanol recovery rate

Table 3 formaldehyde recovery rate

As mentioned above, the present invention utilizes the feature that formaldehyde can react with sodium borohydride to generate methanol under alkaline conditions, and establishes a detection technology for simultaneously detecting the content of formaldehyde and methanol in cosmetics by detecting the content of methanol in the gas phase under equilibrium conditions. And by adding internal standard substance to eliminate the error introduced in the detection process, the sensitivity of detection is improved, and the accurate and rapid detection of formaldehyde and methanol is realized. The method is rapid, objective and accurate, and easy to operate, and is suitable for online control of formaldehyde and methanol in cosmetics and detection of formaldehyde and methanol in commercially available cosmetics. It effectively overcomes the disadvantages of the current detection methods for methanol and formaldehyde in cosmetics.

The implementation of the present invention is not limited by the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods, and are all included in within the protection scope of the present invention.

Claims (7)

1. one kind is quick and precisely detected the formaldehyde in cosmetics and the method for methanol content, it is characterised in that comprise the steps:

Step (1) cosmetic Sample Preparation Procedure:

Sample is added solution of potassium carbonate, then water bath with thermostatic control concussion extraction；

Step (2) sample detection:

Step of learning from else's experience (1) process after sample extraction liquid in different top empty bottle, be then separately added into identical dense in ml headspace bottle After the internal standard substance solution of degree volume and sodium borohydride-internal standard substance solution, gland seals；In head-space sampler after overbalance, By gas chromatographic detection, record methanol and the gas-phase signal value of internal standard substance；

Step (3) methanol standard curve:

Prepare the methanol solution of variable concentrations, be sequentially added in different ml headspace bottle, be simultaneously introduced volatile internal standard substance and carbon Acid potassium solution, then gland seals；In head-space sampler after overbalance, by gas chromatographic detection, draw methanol and interior The gas-phase signal ratio of mark thing and the relation of concentration；

Step (4) interpretation of result:

Formaldehyde In Cosmetics and methanol content is obtained by below equation:

$C_M=800\&times;\frac{R_0-a}{sw}---\left(1\right)$

$C_F=750\&times;\frac{(R_1-R_0)-a}{sw}---\left(2\right)$

W: add the quality of sample, g；

R₀: add in the sample headspace bottle of volatile internal standard substance solution and methanol and internal standard substance signal ratio detected；

R₁: add the methanol and internal standard substance signal ratio detected in the sample headspace bottle of sodium borohydride-volatile internal standard substance solution Value；

The gas-phase signal ratio of s: methanol and internal standard substance and the slope of concentration standard curve；

The gas-phase signal ratio of a: methanol and internal standard substance and the intercept of concentration standard curve.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that In step (1), water bath with thermostatic control concussion temperature is 40 DEG C, and extraction time is more than 60min.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that In step (2), internal standard substance is volatile material, and internal standard substance and sodium borohydride-internal standard substance are dissolved in solution of potassium carbonate.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that Step (2) is dissolved internal standard substance identical with concentration of potassium carbonate in step (1) with the solution of potassium carbonate concentration of sodium borohydride.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that Step (2) head space equilibrium temperature is 105 DEG C, equilibration time 45min, and vibration condition is set to intense oscillations, ml headspace bottle pressing time 10s, quantitative loop filling time 15s, transmit to GC time 20s；

Operating condition during gas chromatographic detection is: hydrion flame detector, and carrier gas is nitrogen, flow velocity 3.8mL/min, pressure 30psi, injector temperature 250 DEG C, capillary column temperature 80 DEG C, do not shunt, detect time 2min.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that Step (3) adds concentration of potassium carbonate identical with potassium carbonate volume in step (2) ml headspace bottle and concentration with volume.

The most quick and precisely formaldehyde in detection cosmetics and the method for methanol content, it is characterised in that The internal standard substance concentration added in step (3) is identical with the internal standard substance added in step (2) with volume.