ES2555161B1 - Procedure for measuring the concentration of chemical species - Google Patents

Abstract

Procedure for measuring the concentration of chemical species of industrial, environmental or biomedical interest through the processing of the RGB values of a digital photograph taken together with a colorimetric sensor and a system of reference standards. It is possible for a user without specialization with a device with any type of camera, with data processing capacity, to carry out the analysis of any chemical species of interest, for example iron in blood. The elimination of ambient noise is possible, allowing the correct analysis from the chemical point of view from a photograph taken under any light condition and with any type of camera. Equally relevant is that the device used is commercial and does not require any adaptation, only of the algorithm that executes the procedure in its part of extracting the data from the photograph and subsequent analysis.

Description

Procedure for measuring the concentration of chemical species

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Object of the invention

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The present invention relates to a method for measuring concentrations of chemical species by means of a chemical analysis to verify and control the concentration of chemical species of industrial, environmental or biomedical interest through the processing of RGB values of a digital photograph taken on sensors calorimetrics that have been contacted with solutions with a known concentration of a certain chemical species (a reference system of standard solutions) and with solutions with an unknown concentration (problem solutions), which you want to measure, of the same chemical species.

Chemical colorimetric sensors, either as solid materials or in solution, have the characteristic of changing color in the presence of chemical species of interest.

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Said solid colorimetric sensors can be contacted with the solution containing the chemical species, either by immersion of the colorimetric sensor in the solution, or by deposition of a sample of the solution on the solid calorimetric sensor. In the case of solution colorimetric sensors, a sample of the solution containing the chemical species to be analyzed is introduced into a vial or cuvette containing the calorimetric sensor solution.

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The automatic digital processing of the photograph taken on the calorimetric sensors that have been in contact with the standard solutions and with the problem solutions, offers as an output the concentration of the species of interest in the unit that the user defines, for example parts by million or molarity, as well as information on the limits in which the concentration is, whether legal or advisable, that is, if it is between, above or below these

limits. Likewise, the present invention has provided for storing a record of the analyzes carried out for the subsequent study of the results or for their re-evaluation, together with the latitude and altitude coordinates that identify the physical place in which the analysis was performed.

The photograph is taken directly, without specific lighting conditions or precautions, so that any user can carry it out, and is independent of the type of digital camera used. This is because the calorimetric sensor that has been in contact with the sample of the solution solution and the colorimetric sensors that have been in contact with the samples of standard solutions are photographed at the same time, carrying out a calibration with each photograph.

Also, the data processing is automatic, so no analytical experience or data processing is required. The digital processing recognizes the shape of the samples of standard solutions and problem solution in each calorimetric sensor, assigning the reference concentration to the first ones, to carry out a calibration using principal components of the RGB values of each standard solution; the three RGB variables of the color shown by each sample of standard solution in contact with calorimetric sensor material are transformed into a main component, as a way of agglutinating the RGB information into a single variable for each sample of standard solution, also reducing noise.

The measuring system is thus calibrated by means of the corresponding adjustment of curves and subsequently the concentration of the chemical species to be analyzed in the problem solution is calculated, by extrapolation of the curve previously adjusted to the main component of the RGB values corresponding to the sample of problem dissolution. Alternatively, the calibration and extrapolation of the measurement can be carried out taking into account only one or two of the RGB parameters, or a mathematical combination of some or all of them.

Technical problem to be solved and Background of the invention

The use of chemical sensors or chemosensors in the determination of chemical species of interest is a mature technology for the assessment and quantification of chemical species in a laboratory of rapid technological evolution (José M. García,

Félix C. Garcia, Felipe Serna, José L. de la Peña, "Fluorogenic and Chromogenic

Polymer Chemosensors ", Polymer Reviews 2011, 51, 341-390; R. Martinez-Máñez, F.

Sancenón, "Fluorogenic and chromogenic chemosensors and reagents for anions",

Chemical Reviews 2003, 103, 4419-4476).

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Moreover, the novel development of solid polymeric calorimetric sensors,

in film form, and easily manageable, by the Group of Polymers of the

Universidad de Burgos has led to the design of sensor materials that allow the

qualitative determination of the concentration of various chemical species so

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visually and quantitatively through various analytical techniques, including analysis

by color of digital photographs by statistical and numerical treatment of

data (S. Vallejos, A. Muñoz, S. Ibeas, F. Serna, F. C. Garcia, J. M. Garcia, "Get out

sensory polymer substrates far the quantification of iron in blood, wine and water by a

scalable RGB technique ", Journal of Materials Chemistry 2013, 1, 15435-15441; J. L.

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Pablos, M. Trigo-López, F. Serna, F. C. Garcia, J. M. Garcia, "Water soluble polymers,

solid polymer membranes, and coated fibers as smart sensory materials for the nak.ed

eye detection and quantification of TNT in aqueous media ~, Chemical Communications

2014, 50, 2484-2487; patent applied for J. L. Pablos, M. Trigo, S. Vallejos, M. A.

Muñoz, L.A. . Sarabia, M.C Ortiz, A. Mendía, F.C. Garda, F. Sema, J.M. Garcia,

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"Solid polymeric materials for the fluorogenic detection of explosives

nitro derivatives and their use ", Application No.: P201400073, Year of

request: 2014).

In carrying out these developments two facts became apparent: a) the potential for

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this type of materials in chemical analysis; b) the need for an automatic system

that will carry out a chemical analysis using the sensor materials from

a simple photograph so that it could be used on site, by anyone, without

specialization, therefore, and that offered finalist information for both this type of

user as for other specialized; that is, in addition to providing a

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quantitative concentration will inform if it is within the limits

appropriate, which may be legal or recommended, depending on the scope of

application of the measure. In this context, the advantage that

it would mean the automatic recording of all analyzes, together with the place of performance,

for its subsequent re-evaluation or elaboration of concentration maps of chemical species in regions of interest.

Traditionally, optical chemical sensors have been used successfully, both based on fluorescence and color variations, on titration and quantification of chemical species of interest in the laboratory. The quantification requires a deep knowledge of the sensor system, as well as a high specialization of both the scientific equipment used to carry out the measurements, specifically ultraviolet / visible spectrophotometers and fluorimeters, as well as data processing by mathematical methods, and specifically statistical. A characteristic example of sensor products that require these characteristics for use is represented by the company Ursa Bioscience (WI / rNrI. Ursa biosci ence.com).

On the other hand, there are numerous commercialized colorimetric sensor kits, such as the 'Test Kits' of the Hanna instruments company (http://wwIN.hannainst.es/catalogo), which are based on a reagent system that produces a color change depending on the concentration of, for example, iron, chlorine, copper, and others in water, and visual contrast with a color scale, or as the "Colorimetric test kits" of Merck Millipore for Aquamerck®, Microquant® and Aquaquant® for analysis of hardness, nitrates, nitrites, phosphate, etc. (http://www.merckmillipore.es/chemicalsl colorimetric-test-kits / spanish / c_JxWb.s10MaIAAAEdThBRbT5Y), or those for water analysis as Quick kits and Visocolor® reagent cases, from Macherey-Nagel (http: //www.mn-net.com) The color change in these kits is visually contrasted with patterns so that the user has qualitative information or semi-quantitative concentrations of species or ranges of conce Introduction The most widespread and characteristic example would be the strips of indicator paper for visual pH control.

Therefore, the use of chemical sensors as a quantitative method of concentration determination currently requires, briefly, a chemical laboratory equipped with spectrophotometers, their maintenance, personnel specialized in chemical and / or clinical analysis, and sample collection and transfer to the laboratory, which implies a high cost in relation to the process and the time between sampling and results. Alternatively, the use of commercial kits entails a subjective assessment of the color by the user and the confrontation against a scale that will lead to a necessarily qualitative numerical value to be interpreted in the context of the analysis, so it also requires some specialization

Description of the invention

The present invention relates to a process for measuring the concentration of chemical species.

As a previous step to the procedure object of the present invention, the following actions are required:

take samples of at least two standard solutions whose concentration of a certain chemical species to be measured, it turns out known; contacting said samples of standard solutions with at least

a first colorimetric chemical sensor, susceptible to color in direct relationship with the concentration of the chemical species to be measured, contained in each of the sample of standard solution; take at least one sample of at least one problem solution, whose concentration of the chemical species to be measured is unknown; contact each sample of problem solution with at least a second calorimetric sensor, of the same characteristics colorimetric than the first colorimetric chemical sensor, susceptible of coloring in direct relation to the concentration of the species Chemistry to be measured, contained in the sample of problem solution.

Next, the process of the present invention introduces the following novel phases:

take at least one photograph of each first calorimetric sensor

contacted each of the samples of the standard solutions and at least one photograph of the second calorimetric sensor contacted with the sample of the problem solution;

•

extract, by means of a device capable of image processing, a representative value of the color, shown in the photographs,

of each first calorimetric sensor brought into contact with each of the samples of the standard solutions and a representative value of the color of the second calorimetric sensor contacted with the sample of the problem solution; associating to each representative value of the color of each first calorimetric sensor in contact with each of the samples of the standard solutions, the known concentration value of the chemical species to be measured in each of the standard solutions; statistically determine a mathematical expression that relates to each other the representative color values of each first colorimetric sensor brought into contact with each of the samples of the standard solutions, together with their corresponding concentration values of the chemical species to be measured; determine, by interpolation of the mathematical expression obtained in the previous step, the concentration value of the chemical species to be measured in the problem solution, corresponding to the representative value of the color of the second colorimetric sensor placed in contact with the sample of the solution trouble.

In a preferred embodiment of the present process, the extraction phase of a color-representative value, shown in the photographs, of each first calorimetric sensor contacted with each of the samples of the standard solutions and the second calorimetric sensor contacted With the sample of the problem solution, it includes:

to.

extract the RGB parameters related to the color, shown in the photographs, of each first calorimetric sensor in contact with each of the samples of the standard solutions and of the second calorimetric sensor in contact with the sample of the problem solution;

b.

determine, by means of a statistical analysis procedure, a representative value of the RGB parameters associated with the color, shown in

the photographs of each first calorimetric sensor placed in contact with the samples of the standard solutions and of the second calorimetric sensor contacted with the sample of the problem solution.

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For this process, an algorithm for recognition of the edges of the images of the samples of standard solutions and problem solutions in contact with the sensor materials of each colorimetric sensor is previously used.

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An algorithm of this type (conventional in the state of the art of image recognition), allows to analyze the color of each one of the zones delimited by the recognized edges.

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For its part, the determination of a representative value of the RGB parameters associated with the color, shown in the photographs, of each first calorimetric sensor contacted with each of the samples of the standard solutions and of the second colorimetric sensor contacted with The sample of the problem solution includes:

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calculate the mutual covariance between the RGB parameters associated with the color, shown in the photographs, of each first colorimetric sensor contacted with each of the samples of the standard solutions and of the second colorimetric sensor contacted with the sample of the problem solution ;

calculate the eigenvalues and eigenvectors attached to the covariance matrix whose values are the covariances calculated in the previous phase;

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determine the representative eigenvector, such as that eigenvector associated with the autovalue of greater absolute value calculated in the previous phase;

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calculate, for each first calorimetric sensor in contact with each of the samples of the standard solutions and for the second colorimetric sensor contacted with the sample of the problem solution, the absolute values of the projections of their associated autovectors, calculated in the previous phase, on the representative autovector determined in the previous phase;

•

determine, for each sample of standard solution and problem solution, the highest of the absolute values calculated in the previous phase;

5 establish each greater of the absolute values determined in the previous phase, respectively as the representative value of the RGB parameters associated with the color, shown in the photographs, of each first calorimetric sensor brought into contact with each of the samples of the standard solutions and of the second calorimetric sensor contacted with

10 sample of the problem solution ,.

In turn, in a preferred embodiment of the present invention, the phase of statistical determination of a mathematical expression that relates to each other the representative color values of each first colorimetric sensor set in

Contact with each of the samples of the standard solutions, together with their corresponding known concentration values of the chemical species (to be measured in the test solution), comprises:

obtain an experimental curve resulting from joining together points associated with

20 each sample of standard dissolution, where the values of the coordinates of each of said points on coordinate axes are respectively the representative value of the color, shown in the photographs, of the first colorimetric sensor brought into contact with the sample of the solution pattern associated with that point and the known value of the species concentration

25 chemistry to be measured in said sample of standard solution:

determine, through an assimilation procedure for least squares

or linear regression, a mathematical expression that represents a curve that closely resembles the experimental curve obtained in the previous phase.

According to a pnmera embodiment, the first calorimetric sensor and the second calorimetric sensor are composed of discs comprising solid chromogenic reactive materials.

According to a second embodiment, the first colorimetric sensor and the second calorimetric sensor are composed of solutions of chromogenic reactive materials that are introduced into vials or cuvettes of transparent or translucent material.

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The procedure object of the present invention provides that the taking of at least one photograph of the first calorimetric sensor and the second colorimetric sensor is carried out by means of a mobile device with an integrated image processor, which is responsible for taking the photograph of the first calorimetric sensor set in contact with the samples of the standard solutions and the second calorimetric sensor placed in contact with the sample of the test solution and determine the concentration value of the chemical species to be measured in the test solution.

Said mobile device can be a smart mobile phone (Smartphone) or a tablet.

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In this way, the procedure can be executed automatically by means of said mobile device, so that a user without knowledge of chemistry or practice in the measurement of dissolved chemical species can carry out the measurement in any type of environmental conditions and lighting of the environment. , without more than photographing the colorimetric sensors after having put them in contact with the samples of standard solutions and problem solutions.

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In a preferred embodiment of the invention, in the phase of taking photographs, the mobile device records together with the concentration values of the chemical species to be measured in the problem solutions, also the data relating to the date, time, latitude , the length and [at altitude of the moment and the place where the test is performed.

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Alternatively, if the measurement of the concentration of a chemical species is made on the body of a patient, the mobile device records together with the concentration values of the chemical species to be measured in the problem solutions, also the data related to the date, the time and anatomical region in which the test is performed.

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In any of the cases mentioned above, the mobile device is expected to offer a representation of a concentration map on a surface

or given geographical or anatomical region, together with the variation of concentrations of the chemical species to be measured in a given period.

The process object of the present invention typically comprises comparing the results obtained from the concentration value of a certain chemical species in a problem solution with characteristic limit values contained in a database, where, as a result of the previous comparison, it is determined if the concentration of a certain chemical species in a problem solution is above or below said characteristic limits. In this way it can be determined if a detected concentration is within the legal and / or advisable limits.

The present invention has as key characteristics that the analysis is carried out through the evaluation of color variations by taking a photograph, and that interference of the type and characteristics of the camera, the light environment and the user is eliminated by taking the photograph together with the reference system of samples of standard solutions and with the samples of problem solutions, together with the calculation of the calibration curve for each measurement, that is, with each photograph.

Likewise, the invention consists in the treatment of the analysis data and its confrontation against relevant tabulated concentration data to indicate if the measured concentration exceeds, is lower, or is among these reference data, which may well be legal or recommended limits. for certain industrial, environmental or biomedical applications.

Likewise, the invention consists in the automatic registration of the altitude and latitude at which the analysis has been carried out so that together with the results of the analysis, the data of the place where they were obtained are also taken, to complete the analysis and develop concentration maps on physical maps.

The analysis of the color variations in each photo containing the reference of standard solutions and the sample of problem solution is carried out by processing the RGB values of the calorimetric sensor material brought into contact

with the solutions, both of the sample of problem solution and of the system of

reference of samples of standard solutions.

Preferably, and non-limitingly before other mathematical treatments, the

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analysis of the three RGB data (red, green and blue) of each of the sensors

calorimetric chemicals included in each photograph (which include the sample of

problem solution and the standard solution sample reference system)

performed by reducing the three RGB variables of each sensor point to one sun to variable,

by main components. With the main component and the concentration of

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the chemical species of interest in the different sensor materials that include the

reference the XY calibration line is constructed, by linear or non-linear adjustment, which

allows to extract the concentration information of the chemical species in the sample

of dissolution problem deposited in the colorimetric sensor. This information is

You can also obtain calibrated directly using any of the

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RGB parameters, or a combination of them.

Once the concentration information is obtained, it is recorded, preferably from

automatically using a mobile device, along with altitude coordinates

and latitude at which the analysis was carried out. In addition, this concentration is

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can automatically compare with the relevant concentration data for the

chemical species of interest and the environment, resulting in information

qualitative of it which, by way of example, can be pass / fail,

meets / does not comply, outside / within range, within / outside the legal limit, within / outside the

advisable limit, etc.

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The process object of the present invention is capable of being implemented.

through an application on a mobile device, which can be connected to a base of

remote data where relevant concentration data are available for

nu evas chemical species, as well as possible updates of existing ones to

30

new values or to different places in the world.

Also, the procedure allows the remote analysis of the photographs taken by

a mobile device, so that the analysis occurs on a different device

and / or located at a certain distance from the place where the photographs have been taken

of the calorimetric sensors that have contacted the solutions

pattern and / or with the problem solutions.

The present invention has the advantage, compared to the mentioned prior art,

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Consistent that the analysis can be performed automatically from the hill

of a photograph taken on a calorimetric sensor that has been placed in

contact with the sample of the chemical species in solution to be measured, or solution

problem, and in a reference system consisting of calorimetric sensors

brought into contact with standard solutions of the chemical species in question; is

10

say for the measurement of each chemical species a reference system is necessary

Specifically designed pattern for said chemical species.

In addition, the reference system for samples of standard solutions placed in

contact with the first calorimetric sensor may be previously prepared, so

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that the measurement of the problem dissolution sample is done simply by putting

in contact this sample solution problem with the second calorimetric sensor and

taking the picture on both colorimetric sensors.

Therefore, preferably the user only intervenes in the commissioning

twenty

contact of the sensor system with the problem solution and in the taking of that photograph,

and this can be taken by anyone without knowledge of chemistry, or

of analysis, not even photography / optics.

The influence of the type of camera, lighting conditions, user, etc., are eliminated

25

by automatically performing the calibration curve with each photo to analyze,

which includes both the reference system of samples of standard solutions placed

in contact with the first colorimetric sensor as the second calorimetric sensor

put in contact with the problem dissolution sample, which represents the key

of the democratization of the analysis system. In addition, the result of the analysis is

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It offers in quantitative terms, which is recorded and is useful for subsequent valuation, as well

as for a more specialized person, and for a set and map study,

and qualitatively indicating whether the result, for example, is within the

legal limits, if a certain water is potable in relation to the chemical species

to be assessed, or if it is within the conventional limits in a biological analysis.

On the other hand, the results are recorded for subsequent evaluations, reassessments or monitoring of evolution, or establishment of concentration maps through the indication of the anatomical or geographical region by latitude and altitude coordinates of each pair of photography / analysis.

In summary, the advantages it presents over existing solutions are:

•

It allows measurements of chemical species in situ and without user intervention in the analysis of the data. Said analysis can be carried out in a fully automated way;

•

the introduction of errors in measurement is avoided due to the existing environmental conditions and due to the photographic device itself, since the captured image encompasses both the reference system formed by the first calorimetric sensor placed in contact with the samples of standard solutions, as with the second colorimetric sensor placed in contact with the sample of the dissolution problem, so that any error or deviation introduced affects the reference system and the second calorimetric sensor placed in contact with the sample of the problem solution equally, since the analysis is It is carried out by comparing the RGB parameters of the second calorimetric sensor in contact with the sample of dissolution problem against the first calorimetric sensor in contact with the samples of the standard solutions. Therefore, these deviations or errors do not affect the final result of the analysis;

•

it is allowed to perform the analysis of the chemical species in real time;

•

this analysis is allowed to be carried out by any person who

have a photographic device without the need for specialized personnel, when performed digitally and automatically, and;

•

a large cost reduction is allowed in relation to conventional photometric quantification techniques.

Brief description of the figures

5

As part of the explanation of the embodiment of the invention, a series of figures have been included, the explanation of which is as follows: Figure 1. It shows a flow chart of an example of embodiment of the procedure for measuring the concentration of chemical species object of the invention. present invention

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Figure 2.- Shows an example of embodiment with the reference system formed by the first colorimetric sensor placed in contact with five samples of standard solutions (P1 to P5) and the second calorimetric sensor placed in contact with a sample to be analyzed for dissolution. problem (P) inserted perpendicular to HIM

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Figure 3.- It shows a mobile device with integrated camera, showing the image of the reference system with the samples of standard solutions, and the sample of problem solution (P).

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Figure 4.- Shows the resulting recognized forms during the edge detection phase of the process object of the present invention.

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Figure 5.- Shows the graphs of a squared minimum adjustment of the points whose coordinates correspond to the known concentrations of the chemical species to be measured in the reference system of standard solutions, and with the main component of the RGB parameters of each of the samples of standard solutions, obtained from the analysis of an image of the first calorimetric sensor captured by the mobile device. This adjustment can be linear or quadratic, the one with the least error being the one used to obtain the value of the problem concentration. Likewise, the point corresponding to the problem solution sample in contact with the second colorimetric sensor is observed; The coordinate of this point relative to the concentration of the chemical species to be measured in the problem solution is obtained by interpolation of the graph obtained by least squares or linear regression.

Figure 6.- Shows the graphs resulting from a least squares adjustment of the

points whose coordinates correspond to the known concentrations of the

chemical species to be measured in the reference system of standard solutions, and with the

main component of the RG8 parameters of each of the samples of

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standard solutions, obtained from the analysis of an image of the first sensor

calorimeter captured by the mobile device under different lighting conditions

to those used for Figure 5. This adjustment can be linear or quadratic, being that of

Less error is used to obtain the value of the problem concentration. Likewise

the point corresponding to the sample of problem solution in contact is observed

10

with the second calorimetric sensor; the coordinate of this point relative to the

concentration of the chemical species to be measured in the problem solution is obtained by

interpolation of the graph obtained by least squares or linear regression.

Figure 7.-Shows a table representing data of the RGB parameters (and their

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main components) of the first calorimetric sensor, brought into contact with

each of the samples of standard solutions. It also shows the parameters

RGB (and its main component) of the second colorimetric sensor brought into contact

with the sample of dissolution problem, as well as the result of the calculation of the

concentration of the chemical species to be measured in said problem solution, obtained

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by interpolation of the graph obtained by linear regression or by minimum

squares, from the representative points of the solution samples

Pattern.

Figure 8.-Sample, for the same samples used in the example of Figure 7,

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but taking the photograph of the samples under other environmental conditions, a

table representing data of the RGB parameters (and their main components) of the

first crometric sensor, put in contact with each of the samples of

standard solutions. It also shows the RGB parameters (and its component

main) of the second calorimetric sensor in contact with the sample of

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problem dissolution, as well as the result of the calculation of the concentration of the

chemical species to be measured in said problem solution, obtained by

interpolation of the graph obtained by linear regression or by least squares, at

from the representative points of the samples of standard solutions.

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Detailed description

.

The flow chart of Figure 1 shows the different stages in which the procedure for measuring the concentration of chemical species of biomedical, environmental and industrial interest is divided.

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At first, the image containing a second colorimetric sensor (2) is captured, which has been contacted with the problem solution, a solution that has an unknown concentration of a specific chemical species whose concentration is to be measured. . Preferably, a photograph of said second calorimetric sensor (2) (in contact with the problem solution) is taken, superimposed on a first calorimetric sensor (1) in contact with at least two samples of standard solutions, which contain a known concentration of the mentioned chemical species to measure.

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In the exemplary embodiment shown in Figure 2, the first calorimetric sensor (1) contains five circular plates, discs or sample holders, with calorimetric sensor material that has come into contact with standard solutions with known concentration of a chemical species whose concentration it is desired to measure in the problem solution.

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This operation is performed by default with the camera integrated in the mobile device (3), although it is also possible to incorporate an image taken with another imported photographic device with standard RGB color format. The result of this operation is seen in Figure 3.

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The samples are then recognized, which includes both samples of standard solutions in counting or the first colorimetric sensor (1), which in the example illustrating the invention are 5, as the sample of problem solution in contact with the sensor material of the second calorimetric sensor (2), as seen in Figures 2 to 4. For this purpose, an edge detection algorithm is used that delimits the circulars corresponding to each sample in circular samples. In the same way it would be done in samples of another format or in liquid samples in vials or cuvettes.

Then, once the regions in which the relevant information is found, a representative value of the color of each of the sensor materials that have come into contact with the standard solutions and

problem dissolution.

Said process is preferably carried out by extracting the parameters or RGB components corresponding to the color of each sample in contact with the corresponding sensor material. Since the color is not uniform in each sample, an average value is calculated in each sample for each component R, G or 8.

10 A representative value of the RGB parameters associated with the color of each of the standard solution and problem solution samples in contact with its corresponding calorimetric sensor is then sought.

1S

He representative value of each color, called in ahead how component

principal of

that color, be gets through a standard statistical procedure

known as principal component analysis. This analysis starts from the matrix of

standardized covariances, which is the result of the calculation of correlations between

RGB channels of each sample of standard solution. Following this procedure

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statistically, the eigenvalues of the covariance matrix are calculated and the

own vector associated with the highest value own value. This own vector serves to

get the main component of each standard color sample with no more to calculate

the scalar product between said own vector and the RGB values of each sample.

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The main component of each of the standard dissolution samples is associated with

its

respective concentration of known value which allows to establish a relationship

functional. This relationship

is obtained from a linear regression or an adjustment

quadratic, as seen in Figure 5, finally taking the one that provides a

minor error

30

In the last step, with the main component of the sample of problem solution or

sample problem, the estimated concentration is obtained from the interpolation of

the functional relationship provided by the previous adjustment. This is a preferred calculation.

but not limiting for the calculation of concentrations from RGB data.

.

The following example is illustrative of the invention, is not intended to be limiting, and describes the determination of the concentration of iron in aqueous medium of a test sample using standards of known concentration for the preparation of the calibration.

Example 1. Calculation of the concentration of Fe (lIl) in aqueous media using a system of 5 standards.

It is based on a system of 6 Fe (lU) sensor discs prepared according to the published procedure (S. Vallejos, A. Muñoz, S. Ibeas, F. Serna, FC García, JM García, "Salid sensory polymer substrates for the quantification of iron in bload, wine and water by a scalable RGB technique ", Joumal af Materials Chemistry 2013, 1,

15435-15441).

Of the 6 discs, 5 discs make up the first calorimetric sensor (1), and are arranged on a support labeled P1 to P5 (see Figure 2 and table of Figure 7) and 30 mL of each disk are added on the surface a known solution of Fe (lIl), between 0 and 6 ppm, (see table shown in Figure 7), buffered at pH = 2. Then 30 mL of a test solution is added, with unknown concentration of Fe (III) , buffered at pH = 2 on a sensor disk in a separate support, constituting the second calorimetric sensor (2), which after adding the solution is inserted perpendicularly in the pattern support, as shown schematically in Figure 2.

In this example, the preparation of the standard is indicated, which once prepared serves for the realization of multiple measurements. This pattern can also be marketed.

Figure 2 corresponds to the image to be photographed by the camera. In it you can distinguish the reference pattern and the sample to be analyzed perpendicularly to it. After a border detection process, the standard and problem samples are recognized (Figure 3). The RGB values shown in the table shown in Figure 7 are extracted from the detected samples.

By means of an analysis in main components, the number of variables from 3 (R, G and B) to a single variable (CP1) of each sample is reduced. The analysis is carried out in conjunction with the samples of standard solutions and with the sample of problem solution. The reduction of variables to a single one fulfills two functions, on the one hand

5 simplifies the subsequent adjustment and extrapolation for the calculation of the concentration of the test sample and, on the other and more important, it represents a significant reduction of noise with a minimum loss of information. Through an adjustment by least squares we can establish a functional relationship between the concentrations of the chemical species in the samples of solutions

10 pattern and the corresponding main component of its RGB parameters. The adjustment that provides a lower error allows us to know the value of the concentration of the chemical species in the problem solution, by extrapolation.

The result indicates that the concentration of the test solution sample was 15 50.5 ppm, with an error of less than 2% compared to the concentration estimated by atomic absorption spectroscopy, proven analytical technique.

It is especially relevant to indicate that this procedure, when calculating the calibration curve in each measurement with the RGB data treated from the samples of 20 standard solutions, and extrapolating with those of the sample of the solution solution, offers the same result in different devices, environmental conditions and users, eliminating these interferences and allowing the use of commercial electronic devices, without any adaptation or support. That is, the RGB data of each sample will vary from one analysis to another depending on the conditions mentioned,

25 but the valuation curve of these data with the known concentrations of the standard solution samples will result in the same concentration value of the test solution sample.

Example 2. Calculation of the concentration of the test solution sample of Example 30 taking the picture in different environmental conditions.

To illustrate the independence of the result with the environmental conditions, a photograph is taken with a conventional camera under other conditions to the analysis system described in Example 1: it is imported into the mobile analysis device (3) used in Example 1, and it is processed, resulting in the one shown in the table in Figure 8.

In the tables of Figures 7 and 8, the concentration value of the test solution sample is measured by atomic absorption spectroscopy to check the goodness of the calculated result.

The result indicates that the concentration of the test solution sample was

49.96 ppm, with an error of less than 1% with respect to the concentration estimated by 10 atomic absorption spectroscopy, proven analytical technique.

Concordance with the result of Example 1 is appreciated.

"

Claims (11)

1. Procedure for measuring the concentration of chemical species comprising: take samples of at least two standard solutions whose concentration of a certain chemical species to be measured, it turns out known; contacting each of said samples respectively standard solutions with at least one first calorimetric sensor (1), liable to color in direct relation to the concentration of the chemical species to be measured, contained in each dissolution sample Pattern; take at least one sample of at least one problem solution, whose concentration of the chemical species to be measured is unknown; contact each sample of problem solution with at least a second colorimetric sensor (2), of the same characteristics calorimetric than the first calorimetric sensor (1), susceptible to color in direct relation to the species concentration chemistry to be measured, contained in the test solution sample; characterized in that it additionally comprises: take at least one photograph of each first calorimetric sensor (1), brought into contact with each of the standard solutions, and at least one photograph of the second calorimetric sensor (2), contacted with the problem solution; extract, by means of an image-capable device, a representative color value, shown in the photographs, of each first calorimetric sensor (1) placed in contact with each of the samples of the standard solutions, and of the second calorimetric sensor (2) contacted the problem solution; associate each representative color value of each first calorimetric sensor (1) in contact with each of the samples of

standard solutions, the known concentration value of the species

chemistry to be measured in each of the standard solutions;

statistically determine a mathematical expression that relates

each other the representative values of the color, shown in the

s

photographs of each first colorimetric sensor (1) contacted

with each of the samples of standard solutions, together with their

corresponding values of known concentration of the species

chemistry to be measured;

determine, by interpolation of the mathematical expression obtained

10

in the previous step, the concentration value of the chemical species a

measure in the problem solution, corresponding to the value

representative of the color of the second calorimetric sensor (2) set to

Contact with the sample of problem solution.

fifteen

2. Procedure for measuring the concentration of chemical species according to

claim 1, characterized in that the phase of extracting a value

representative of the color of each first colorimetric sensor (1) set to

contact with each of [the samples of the standard solutions and the

second co-orimetric sensor (2) placed in contact with the sample of [a

twenty

Problem solution includes:

to. extract RGB parameters related to color, shown in the

Totographs of each first calorimetric sensor (1) put in contact

with each of the samples of the standard and second solutions

25

colorimetric sensor (2) placed in contact with the dissolution sample

trouble;

b. determine, by means of a statistical analysis procedure, a value

representative of the RGB parameters associated with [color, shown in

30

the photographs of each first calorimetric sensor (1) placed in

contact with each of the samples of the standard solutions and the

second calorimetric sensor (2) placed in contact with the sample of

problem dissolution.

2. 3

3.

Procedure for measuring the concentration of chemical species according to

claim 2, characterized in that the determination of a value

representative of the RGB parameters associated with the color, shown in the

photographs, of each first calorimetric sensor (1) contacted

5

each of the samples of the standard solutions and the second sensor

calorimeter (2) placed in contact with the test solution sample

understands:

a) calculate the mutual covariance between the RGB parameters associated with the

10

color, shown in the photographs, of each first calorimetric sensor

(1) contacted each of the samples of the

standard solutions and the second calorimetric sensor (2) set to

contact with the sample of problem solution;

fifteen

b) calculate the eigenvalues and eigenvectors associated with the matrix of

covariance whose values are the covariances calculated in the phase

previous;

c) determine a representative autovector, such as that autovector

twenty

associated with the highest absolute value autovalue calculated in the phase

previous;

d) calculate, for each first colorimetric sensor contacted with

each of the samples of the standard solutions and for the second

25

colorimetric sensor placed in contact with the dissolution sample

problem, the absolute values of the projections of their

associated autovectors, calculated in the previous phase, on the

representative autovector determined in the previous phase;

30

e) determine, for each first calorimetric sensor placed in contact

with each of the samples of the standard solutions and for the

second calorimetric sensor placed in contact with the sample of

problem solution, the largest of the absolute values calculated in the

previous phase;

24

f) establish each of the higher absolute values determined in the previous phase, respectively as the representative value of the RGB parameters associated with the color, shown in the photographs, of each first calorimetric sensor (1) put in contact with each of the samples of the standard solutions and the second calorimetric sensor (2) placed in contact with the sample of the problem solution. 4. Method for measuring the concentration of chemical species according to claim 1, characterized in that the phase of statistical determination of a mathematical expression that relates to each other the representative values of the color, shown in the photographs, of each first calorimetric sensor (1 ) placed in contact with each of the samples of the standard solutions, together with their corresponding concentration values of the chemical species to be measured, comprises:

to.

Obtain an experimental curve resulting from joining points associated with each sample of standard dissolution, where the values of the coordinates of each of these points in some coordinate axes are respectively the representative value of the color, shown in the photographs, of the first colorimetric sensor (1) placed in contact with the sample of the standard solution associated with said point and the known value of the concentration of the chemical species to be measured in said standard solution;

b.

determine, through a method of assimilation by least squares or linear regression, a mathematical expression that represents a curve that closely resembles the experimental curve obtained in the previous phase.

5.

Method for measuring the concentration of chemical species according to claim 1, characterized in that the first colorimetric sensor (1) and the second calorimetric sensor (2) are composed of disks comprising solid chromogenic reactive materials.

6.

Method for measuring the concentration of chemical species according to claim 1, characterized in that the first calorimetric sensor (1) and the second calorimetric sensor (2) are composed of solutions of

5 chromogenic reactive materials that are introduced into vials or cuvettes of translucent materials. 7. Method for measuring the concentration of chemical species according to claim 1, characterized in that the taking of at least one photograph of the first calorimetric sensor (1) and the second calorimetric sensor (2) is carried out by means of a mobile device (3 ) with an integrated image processor, which is responsible for taking the photograph of the first calorimetric sensor (1) placed in contact with the samples of the standard solutions and of the second colorimetric sensor (2) contacted with the sample of the problem solution, 15 and determine the concentration value of the chemical species to be measured in the problem solution. 8. Procedure for measuring the concentration of chemical species according to claim 7, characterized in that the mobile device (3) is a smart phone or a tablet. 9. Method for measuring the concentration of chemical species according to claim 7, characterized in that the mobile device (3) records the concentration values of the chemical species to be measured in the solutions 25 problem, together with the data related to the date, time, latitude, longitude and allilud of the moment and the place where the test is performed. 10. Method for measuring the concentration of chemical species according to claim 7, characterized in that the mobile device (3) records the 30 concentration values of the chemical species to be measured in the solutions problem, together with data related to the date, time and anatomical region in which the test is performed. 11. Method for measuring the concentration of chemical species according to claims 9 and 10, characterized in that the mobile device (3) offers a representation of a map of concentrations on a given surface or region, together with the variation of concentrations of the species s chemical to be measured in a given period. 12. Method for measuring the concentration of chemical species according to claims 1, characterized in that it comprises comparing the results obtained from the value of the concentration of a particular chemical species in a problem solution with characteristic limit values contained in a database, where, as a result of the previous comparison, it is determined whether the concentration of a certain chemical species in a problem solution is above or below said characteristic limits.