A detection method for simultaneously determining multiple phthalates

Abstract

The present invention discloses a detection method for simultaneously determining a variety of phthalates, and relates to the technical field of chemical analysis. The method comprises the following steps: using dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate as standard substances, and then mixing each standard solution in a certain proportion to form a mixed standard solution; establishing an MLR-spectrophotometric concentration prediction model; using the prediction model to determine the concentrations of dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate in an unknown concentration solution. The present invention combines multiple linear regression analysis with spectrophotometry, can overcome the problems of spectral overlap and mutual interference between components, and provides a simple and convenient chemometric method for the simultaneous determination of multiple PAEs by spectrophotometry, which can be applied to environmental monitoring and automatic analysis of plasticizers in actual work.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to a detection method for simultaneously determining a plurality of phthalate substances. Background Art

[0002] Phthalic acid esters (PAEs), also known as phthalic acid esters, are a general term for about 30 compounds. They are formed by the esterification of phthalic anhydride and alcohol under acid catalysis. They are a class of chemicals that can soften and are mainly used as plasticizers in plastic production to improve the plasticity and flexibility of plastics. PAEs contain weak estrogen components, which can affect the endocrine system, mutagenesis, teratogenesis and cancer cell proliferation of organisms. They are a class of environmental hormones that can enter the human body through breathing, diet and skin contact, causing harm to human health. In recent years, with the improvement of instrumental analysis, more and more PAEs detection methods have been developed. The main detection methods are: gas chromatography-mass spectrometry, gas chromatography, high performance liquid chromatography, etc. However, due to instrument limitations, many enterprises and institutions cannot have high-end analytical instruments, and there are limitations in the analysis and detection of PAEs plasticizers. Therefore, it is necessary to explore a simple spectrophotometric detection method that is conducive to the determination and analysis of various enterprises and institutions.

[0003] The most commonly used PAEs plasticizers in the market are: dioctyl phthalate (DOP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), etc. Spectrophotometry is usually used for the determination of a single component. In multi-component analysis, spectral overlap may occur, which seriously interferes with the determination. Although the interference can be removed by adding masking agents or performing separation treatment before detection, the operation is complicated, chemical reagents are wasted, and new interference may be introduced, resulting in low efficiency. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies in the above-mentioned background technology and provide a detection method for simultaneously determining multiple phthalates. The method combines multiple linear regression analysis with spectrophotometry, which can overcome the problems of spectral overlap and mutual interference between components, and provides a simple and convenient chemometric method for simultaneously determining multiple PAEs by spectrophotometry, which can be applied to environmental monitoring and automatic analysis of plasticizers in actual work.

[0005] The object of the present invention is to provide a detection method for simultaneously determining multiple phthalates, comprising the following steps:

[0006] Prepare mixed standard solution: use dioctyl phthalate (DOP), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) as standard substances, prepare standard solutions of each standard substance with organic solvents respectively; then mix each standard solution in a certain proportion to prepare a mixed standard solution;

[0007] Establish a multiple linear regression (MLR)-spectrophotometric concentration prediction model: Then use an ultraviolet spectrophotometer to scan the wavelength of each standard solution and the mixed standard solution to obtain the absorbance value; import the concentration, scanning band and absorbance value of the mixed standard solution into the MLR program package in MATLAB to establish a prediction model;

[0008] The prediction model was used to determine the concentrations of DOP, DBP and BBP in solutions of unknown concentrations.

[0009] Preferably, the organic solvent is methanol.

[0010] More preferably, in the process of preparing the standard solution, each standard substance is separately diluted with methanol to prepare a stock solution of each standard substance, and then each stock solution is diluted with methanol to form a standard solution of different concentrations.

[0011] More preferably, the concentration of the stock solution of each standard substance is 200 mg / L.

[0012] Preferably, the scanning wavelength range is 185-250 nm.

[0013] Preferably, during the absorbance measurement, methanol reagent is used as a reference.

[0014] Preferably, the established prediction model is verified by the absorbance of a mixed sample of DOP, DBP, and BBP with known concentrations, and the relative deviation of the substance concentration is analyzed and calculated, and the relative deviation is used to correct the measured solution concentration.

[0015] Preferably, in the process of establishing the MLR-spectrophotometric concentration prediction model, the MLR program is automatically calculated by running MATLAB, and the absorbance of the mixed standard solution of DOP, DBP, and BBP in the 185-250nm band, the scanning band, and the concentrations of the three substances in the mixed standard solution can be used to obtain the following regression equation: w , b w 、c w ,d w Unknown parameters, establish a prediction model for the concentrations of three substances, DOP, DBP, and BBP, in the mixed solution;

[0016] The regression equation obtained is: w X 1 +b w X 2 +c w X 3 +d w W=Q w R 2

[0017] Among them: a w , b w 、c w ,d w is the partial regression coefficient;

[0018] Q w is the absorbance of the solution at wavelength W;

[0019] R 2 is the correlation of the obtained fitting equation;

[0020] X 1 X 2 X 3 They represent the concentrations of dioctyl phthalate, di-n-butyl phthalate and butyl benzyl phthalate respectively.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a detection method for simultaneously determining multiple phthalates. The method combines multiple linear regression analysis (MLR) with spectrophotometry, which can overcome the problems of spectral overlap and mutual interference between components, and provides a simple and convenient chemometric method for simultaneously determining multiple PAEs by spectrophotometry, which can be applied to environmental monitoring and automatic analysis of plasticizers in actual work.

[0023] The method provided by the present invention for simultaneously determining the three elements of DOP, DBP and BBP is as follows: accurately draw 20 μL of DOP, DBP and BBP into a 100 mL volumetric flask, dilute with methanol, and prepare DOP, DBP and BBP stock solutions with a mass concentration of 200 mg / L respectively; measure the stock solutions, and use methanol to dilute a series of single standard solutions and mixed standard solutions of DOP, DBP and BBP with different mass concentrations. Use an ultraviolet spectrophotometer to perform band scanning on the single standard solution and the mixed standard solution with methanol reagent as a reference, import the concentration, scanning band and absorbance value of the mixed standard solution into the MLR program package in MATLAB, and establish a DOP, DBP and BBP concentration prediction model of MLR-spectrophotometry;

[0024] The present invention has substantial characteristics and significant progress. The present invention combines MLR with spectrophotometry, giving full play to the convenient and fast method of spectrophotometry, and simplifies the chemical treatment process when multiple components are measured simultaneously. The use of MLR to solve the problem of spectral overlap between DOP, DBP, and BBP elements can not only provide a simple and convenient chemometric method for the simultaneous determination of multiple PAEs by spectrophotometry, but also can be extended to the analysis field of other PAEs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The absorbance curve of the gradient series of DOP single standard solution 1-6 in Table 1;

[0026] Figure 2 The absorbance curve of the gradient series of DBP single standard solution 1-6 in Table 1;

[0027] Figure 3 This is the absorbance curve of the gradient series of groups 1-6 of the BBP single standard solution in Table 1. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments, but the embodiments are not intended to limit the present invention.

[0029] It should be noted that the experimental methods in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0030] The experimental instrument used in the present invention is: UV-2600i ultraviolet-visible spectrophotometer, produced by Shimadzu Corporation of Japan.

[0031] Example 1

[0032] Establishment of MLR-spectrophotometry

[0033] Preparation of standard solution

[0034] Accurately pipette 20 μL of DOP, DBP, and BBP into a 100 mL volumetric flask, dilute to volume with methanol, and prepare DOP, DBP, and BBP stock solutions with a mass concentration of 200 mg / L respectively; measure the stock solutions and use methanol to dilute a series of DOP, DBP, and BBP single standard solutions and mixed standard solutions with mass concentrations shown in Tables 1 and 2 in 50 mL colorimetric tubes.

[0035] Table 1 is the single standard solution of DOP, DBP and BBP

[0036]

[0037]

[0038] Table 2 is the mixed standard solution of DOP, DBP and BBP

[0039]

[0040] Spectrophotometric detection technology

[0041] Use a UV spectrophotometer to scan a single standard solution with methanol reagent as a reference in a 1 cm cuvette over a wavelength range of 185-300 nm, and measure the absorbance of the solution every 1 nm. Figures 1 to 3 shown.

[0042] Figure 1 This is the gradient series of DOP single standard solution 1-6 in Table 1. It can be seen from the figure that as the concentration of DOP standard solution increases, the corresponding absorbance value also increases, and the maximum absorption wavelength of DOP solution is 201nm.

[0043] Figure 2 This is the gradient series of DBP single standard solution 1-6 in Table 1. It can be seen from the figure that as the concentration of DBP standard solution increases, the corresponding absorbance value also increases, and the maximum absorption wavelength of DBP is 201nm.

[0044] Figure 3 This is the gradient series of groups 1-6 of the single standard solution of BBP in Table 1. It can be seen from the figure that as the concentration of the BBP standard solution increases, the corresponding absorbance value also increases, and the maximum absorption wavelength of BBP is 190nm.

[0045] Depend on Figure 1 , 2 , 3, we can see that DOP, DBP, and BBP have maximum absorption values ​​at 201nm, 201nm, and 190nm, respectively, and the maximum absorption wavelengths of the three seriously overlap, so 185-250nm is selected to establish the MLR prediction model.

[0046] Establishment of MLR prediction model

[0047] The role of the prediction model: The prediction model is established based on the known relationship between the concentration and absorbance of the mixed solution of three substances DOP, DBP, and BBP; then, the model is used to predict the concentrations of the three substances in the unknown mixed solution when the absorbance of the mixed solution of the three substances DOP, DBP, and BBP is known. The specific model is established as follows:

[0048] Using an ultraviolet spectrophotometer, selecting a wavelength range of 185-250 nm, the 16 groups of mixed standard solutions of DOP, DBP, and BBP shown in Table 2 were scanned to obtain the absorbance values ​​of the 16 groups of mixed standard solutions of DOP, DBP, and BBP in the 185-250 nm band.

[0049] The MLR program is automatically calculated by running MATLAB. The absorbance of the mixed standard solution of DOP, DBP, and BBP in the 185-250nm band, as well as the known concentrations of the three substances in the scanning band and the mixed solution can be used to obtain the following regression equation: w , b w 、c w ,d w Unknown parameters, a prediction model for the concentrations of three substances DOP, DBP and BBP in the mixed solution was established.

[0050] The regression equation obtained is: w X 1 +b w X 2 +c w X 3 +d w W=Q w R 2

[0051] Among them: a w , b w 、c w ,d w is the partial regression coefficient;

[0052] Q w is the absorbance of the solution at wavelength W;

[0053] R 2 is the correlation of the obtained fitting equation;

[0054] X 1 X 2 X 3 They represent the concentrations of dioctyl phthalate, di-n-butyl phthalate and butyl benzyl phthalate respectively.

[0055] The specific program analysis process is as follows: input independent variables (the concentration of each of the three substances in the mixed solution), dependent variables (absorbance of the mixed solution in the 185-250nm band) → perform multiple linear regression analysis → obtain regression equation → establish a prediction model → measure solutions of unknown concentrations.

[0056] The purpose of establishing this model is to predict the concentration of each of the three substances in an unknown mixed solution when the absorbance of the mixed solution of the three substances in a certain band is known.

[0057] The ranges of DOP, DBP and BBP measured by the method provided in this embodiment are: 0.5-1.4 mg / L, 0.4-1.4 mg / L and 0.6-1.2 mg / L respectively.

[0058] Example 2

[0059] The method provided in Example 1 was used to test the concentrations of DOP, DBP and BBP in a mixed solution to illustrate the reproducibility and accuracy of the method provided by the present invention.

[0060] Six groups of mixed solutions of three substances of DOP, DBP and BBP within the measurement range were prepared respectively. The concentration preparation is shown in Table 3. The concentrations of DOP, DBP and BBP substances were measured three times according to the measurement steps provided in Example 1. The relative standard deviations were 6.02%, 9.13% and 9.40%, respectively. The spiked recoveries were 104.26%, 94.66% and 97.65%, respectively. The data are shown in Table 4.

[0061] Table 3 is the prepared mixed solution of DOP, DBP and BBP

[0062]

[0063]

[0064] Table 4: Data related to the determination of the mixed solution of DOP, DBP and BBP in Table 3 according to the steps provided in Example 1

[0065]

[0066] Note: MRE (%) is the relative standard deviation

[0067] From Table 4, it can be seen that the method provided by the present invention has a certain reproducibility from the three prediction results and their average values; from the relative standard deviation of the prediction results and the spiked recovery rate, it can be seen that the method has a high accuracy.

[0068] Other explanations about the MLR prediction model: Multiple regression analysis refers to the use of regression equations to quantitatively explain the linear dependency between a dependent variable and two or more independent variables. Its basic idea is to try to find the mathematical expression that best represents the relationship between the independent variable and the dependent variable.

[0069] To establish a multivariate linear regression model, we first need to measure the degree of correlation between multiple explanatory variables and the explained variables through correlation analysis, and retain the variables with significant correlation.

[0070] Secondly, in order to further study the influence relationship and influence degree of each variable on the dependent variable, the stepwise regression method is usually used to select the independent variables that have a significant impact on the dependent variable one by one. (The basic idea of ​​the stepwise regression method is to introduce independent variables one by one and perform an F test on each independent variable. If the original introduced independent variable becomes no longer significant due to the later introduced independent variable, the original introduced independent variable is eliminated, and this process is repeated until no significant independent variables are introduced and no insignificant independent variables are eliminated from the regression equation.) After obtaining the regression equation based on the stepwise regression method, the linear regression effect of the model is usually measured based on the coefficient of determination. The coefficient of determination refers to the ratio of the regression sum of squares to the deviation sum of squares. The larger the proportion of the regression sum of squares, the better the goodness of fit between the regression line and the sample data, and the better the model regression effect.

[0071] Finally, in order to establish a simpler regression equation and eliminate an independent variable that has no significant effect on the dependent variable, it is necessary to conduct a significance test of the regression coefficient of the multivariate linear regression equation; this can be done using a t-test, multiple co-occurrence test, or residual analysis.

[0072] In summary, the present invention provides a detection method for simultaneously determining multiple phthalates. The method combines multiple linear regression analysis (MLR) with spectrophotometry, which can overcome the problems of spectral overlap and mutual interference between components, and provides a simple and convenient chemometric method for simultaneously determining multiple PAEs by spectrophotometry, which can be applied to environmental monitoring and automatic analysis of plasticizers in actual work.

[0073] The method provided by the present invention for simultaneously determining the three elements of DOP, DBP and BBP is as follows: accurately draw 20 μL of DOP, DBP and BBP into a 100 mL volumetric flask, dilute with methanol, and prepare DOP, DBP and BBP stock solutions with a mass concentration of 200 mg / L respectively; measure the stock solutions, and use methanol to dilute a series of single standard solutions and mixed standard solutions of DOP, DBP and BBP with different mass concentrations. Use an ultraviolet spectrophotometer to perform band scanning on the single standard solution and the mixed standard solution with methanol reagent as a reference, import the concentration, scanning band and absorbance value of the mixed standard solution into the MLR program package in MATLAB, and establish a DOP, DBP and BBP concentration prediction model of MLR-spectrophotometry;

[0074] The present invention has substantial characteristics and significant progress. The present invention combines MLR with spectrophotometry, giving full play to the convenient and fast method of spectrophotometry, and simplifies the chemical treatment process when multiple components are measured simultaneously. The use of MLR to solve the problem of spectral overlap between DOP, DBP, and BBP elements can not only provide a simple and convenient chemometric method for the simultaneous determination of multiple PAEs by spectrophotometry, but also can be extended to the analysis field of other PAEs.

[0075] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for simultaneously determining multiple phthalates, characterized in that: The following steps are involved: Preparation of mixed standard solution: using dioctyl phthalate, di-n-butyl phthalate and butyl benzyl phthalate as standard substances, respectively prepare standard solutions of each standard substance with organic solvents; then mix each standard solution in a certain proportion to prepare a mixed standard solution; Establishing the MLR-spectrophotometric concentration prediction model: using an ultraviolet spectrophotometer to scan the wavelength of each standard solution and the mixed standard solution to obtain the absorbance value; importing the concentration, scanning band and absorbance value of the mixed standard solution into the MLR program package in MATLAB to establish the prediction model; The prediction model was used to determine the concentrations of dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate in solutions of unknown concentrations. In the process of establishing the MLR-spectrophotometric concentration prediction model, the MLR program was automatically calculated by running MATLAB, and the absorbance value of the mixed standard solution of dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate in the 185-250nm band, the scanning band, and the concentrations of the three substances in the mixed standard solution were used to obtain the following regression equation: w , b w 、c w ,d w For unknown parameters, a prediction model for the concentrations of three substances, dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate, in a mixed solution was established; The regression equation obtained is: w X1+b w X2+c w X3+d w W=Q w R 2 Among them: a w , b w 、c w ,d w is the partial regression coefficient; Q w is the absorbance of the solution at wavelength W; R 2 is the correlation of the obtained fitting equation; X1, X2, and X3 represent the concentrations of dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate, respectively.

2. The method for simultaneously determining multiple phthalates according to claim 1, characterized in that: The organic solvent is methanol.

3. The method for simultaneously determining multiple phthalates according to claim 2, characterized in that: In the process of preparing the standard solution, each standard substance is separately diluted with methanol to form a stock solution of each standard substance, and then each stock solution is diluted with methanol to form a standard solution of different concentrations.

4. The method for simultaneously determining multiple phthalates according to claim 3, characterized in that: The concentration of the stock solution of each standard substance was 200 mg / L.

5. The method for simultaneously determining multiple phthalates according to claim 1, characterized in that: The scanning wavelength range is 185-250 nm.

6. The method for simultaneously determining multiple phthalates according to claim 1, characterized in that: During the absorbance measurement, methanol reagent was used as a reference.

7. The method for simultaneously determining multiple phthalates according to claim 1, characterized in that: The established prediction model was verified by testing the absorbance of a mixed sample of dioctyl phthalate, di-n-butyl phthalate, and butyl benzyl phthalate with known concentrations. The relative deviation of the substance concentration was analyzed and calculated, and the relative deviation was used to correct the measured solution concentration.

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