CN114414713B - Method for extracting and detecting main PAEs in tea based on response surface method optimization - Google Patents
Method for extracting and detecting main PAEs in tea based on response surface method optimization Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/88—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
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Abstract
The invention provides a method for extracting and detecting main PAEs in tea based on response surface method optimization. Phthalate esters (PAEs) are mainly used as plasticizers, and in small amounts as additives for washing and caring products and cosmetics, the products made from raw materials are millions. It interferes with endocrine system of human body, and has teratogenic, oncogenic and mutagenic potential. However, the amount is small and is not easy to detect. The invention is extracted and concentrated by an organic solvent, and then is purified by solid phase extraction and detected by GC-MS. The method is based on optimization of the extraction conditions of the main PAEs in the tea, has the advantages of strong pertinence, simple and convenient operation and high accuracy, is particularly suitable for measuring the content of 5 PAEs in the tea, has good accuracy, provides scientific basis for quality control and safety evaluation of the tea, and has important significance for monitoring and preventing the pollution of the PAEs in the tea.
Description
Technical Field
The invention belongs to the field of detection of environmental pollutants in tea, and relates to a method for extracting and detecting 5 phthalic acid esters in tea.
Background
Phthalate esters (PHTHALIC ACID ESTERS, PAEs) are a material aid for enhancing flexibility, and are widely applied to plastic products, accounting for 80% of the total amount of plasticizers. Since PAEs have teratogenic, oncogenic and mutagenic potential, the maximum addition of PAEs in plastic products must not exceed 30%. Because PAEs are not chemically bound to the polymer matrix, they are very easy to release into the environment, and are difficult to degrade, threatening the health of humans. The U.S. environmental protection agency lists 6 PAEs, dimethyl phthalate (DIMETHYL PHTHALATE, DMP), diethyl phthalate (DIETHYL PHTHALATE, DEP), and Di (2-ethyl) hexyl phthalate (Di (2-ethyl) hexyl phthalate, DEHP), as the priority control toxic contaminants. The Chinese also brings out a plurality of related standards and regulations, strengthens the prevention and control of the pollution risk of the food PAEs, and ensures the food safety.
Tea leaves are one of the most popular non-alcoholic beverages in the world, and are consumed in amounts and in yields inferior to water. The area of the tea garden in China is 4700 tens of thousands of mu, the annual output of tea leaves is approximately 300 tens of thousands of tons, and the tea garden is the first, first and second place in the world in large countries of world tea production, consumption and export. The tea industry has become an important pillar industry and an dominant industry for export foreign exchange in rural economy in the main production area. With the rapid development of tea industry, tea quality safety becomes an important bottleneck for restricting the development of industry. Tea trees are used as perennial evergreen plants, can be polluted by various sources in the processes of planting, processing, packaging and storing, and have the characteristics of strong tea adsorption activity, long production and processing processes and the like, and PAEs can be continuously enriched in tea, so that potential safety hazards of tea quality are caused. The research shows that PAEs are detected in fresh tea leaves, green tea, black tea, dark tea and other tea products, and the detection rate is up to 100%. The PAEs are a widely-existing persistent organic pollutant, so that the detection method of the PAEs in the tea is established and perfected as soon as possible, and theoretical basis and detection means can be provided for preparing relevant policy standards and further controlling the content of the PAEs in the food, which are unprecedented.
Along with the improvement of living standard and the enhancement of safety consciousness in recent years, the related standards and specifications of tea are increasingly strict, and the quality and safety of tea are closely concerned by China and even the world. At present, the inspection strength of PAEs in the food field at home and abroad is increased year by year, the maximum residual limit and detection standard are regulated in wine and grease foods, but the relevant regulations on tea are not formulated, and further intensive research is needed for improving the detection method of PAEs in tea to improve the sensitivity and precision of detection.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for extracting and detecting main phthalic acid esters in tea based on a response surface optimization method.
The invention firstly provides a response surface method-based optimized method for extracting and detecting main PAEs in tea, which comprises the following steps:
1) Establishing a tea sample PAEs extraction flow
The PAEs extraction flow is as follows: adding n-hexane into the tea sample to be tested according to a certain feed liquid ratio, performing ultrasonic extraction, standing the extract at a certain temperature for a certain time, concentrating by reduced pressure distillation, and performing solid phase extraction, purification and elution; the solid phase extraction column adopted by the solid phase extraction is a graphitized carbon black and amino mixed filler solid phase extraction glass column;
2) Optimization of PAEs (polycyclic aromatic hydrocarbon) extraction condition response surface of tea sample
Setting three factors of different feed-liquid ratios, different extraction standing time after ultrasonic treatment and different extraction standing temperature after ultrasonic treatment, and performing a single factor test; based on a single factor test, taking the feed liquid ratio (A), the post-ultrasonic extraction standing temperature (B) and the post-ultrasonic extraction standing time (C) as response surface test independent variables, taking the extraction quantity (R) of PAEs in the tea as a response value, performing Box-Behnken optimization treatment, and determining the optimal extraction condition of the PAEs in the tea through analysis of variance and response contour map analysis;
3) Extraction and detection of main PAEs in tea
And (3) for a tea sample to be detected, extracting the PAEs by adopting the extraction flow of the step (1) under the optimal extraction conditions of the PAEs in the tea obtained in the step (2), detecting the PAEs by using a gas chromatograph-mass spectrometer, and calculating according to the standard working curve of each phthalate compound to obtain the detection content.
In the step 2), the optimal extraction conditions of the PAEs in the tea are determined through analysis of variance and analysis of response contour map, and the optimal extraction conditions are specifically as follows:
The response surface graph is a three-dimensional space curved surface graph formed by the PAEs extraction amount in the tea and each influence factor, and the steeper the curve is, the larger the influence of the influence factors on the PAEs extraction amount in the tea is; performing multiple regression fitting by using Design-ExertV8.0.6 software, and establishing multiple regression equations of PAEs extraction amount and feed liquid ratio (A), post-ultrasonic extraction standing temperature (B) and post-ultrasonic extraction standing time (C) in tea;
And obtaining the optimal extraction condition of the PAEs in the tea according to a quadratic regression equation.
As a preferable scheme of the invention, in the optimal extraction condition of PAEs in the tea obtained in the step 2), the feed liquid ratio of the tea sample to the n-hexane is 1:20, and the unit of the feed liquid ratio is g/ml.
As a preferred scheme of the invention, in the optimal extraction condition of PAEs in the tea obtained in the step 2), the tea is subjected to ultrasonic treatment and then is kept stand for 12 hours at 40 ℃.
As a preferable scheme of the invention, the ultrasonic treatment in the step 1) is ultrasonic treatment at 40 ℃ for 3 hours, and then standing is carried out.
As a preferable scheme of the invention, the solid phase extraction column is activated by adopting acetonitrile and toluene mixed solution with the volume ratio of 3:1, and is eluted by adopting acetonitrile and toluene mixed solution with the volume ratio of 3:1.
In the preferred embodiment of the present invention, in step 3), the eluent obtained by solid phase extraction purification is distilled to dryness under reduced pressure, cooled, n-hexane is added, and then detection is performed by a gas chromatograph-mass spectrometer.
As a preferred embodiment of the present invention, the gas chromatography conditions are: the chromatographic column is an HP-5MS quartz capillary column with the dimensions of 30.0m multiplied by 250 μm multiplied by 0.25 μm; the temperature of the sample inlet is 280 ℃; sample introduction without diversion; the sample injection amount is 1 mu L; the carrier gas is high-purity helium, the constant flow rate is 1.0mL/min; the temperature program is as follows: the initial temperature is 80 ℃, kept for 1min, and is raised to 140 ℃ at 6 ℃/min, kept for 2min, and is raised to 150 ℃ at 2 ℃/min, kept for 2min, and is raised to 180 ℃ at 5 ℃/min, kept for 1min, and is raised to 250 ℃ at 6 ℃/min, kept for 1min, and is raised to 270 ℃ at 3 ℃/min, and kept for 1min at 270 ℃.
As a preferred embodiment of the present invention, mass spectrometry conditions are: the ionization mode is electron bombardment ionization source (EI); ionization energy is 70eV; the temperature of the transmission line is 280 ℃; the ion source temperature is 230 ℃; delaying the solvent for 5min; the detection mode is selected ion Scanning (SIM).
Compared with the prior art, the invention further improves the extraction rate of PAEs in the tea, adopts a response surface optimization analysis method, performs multiple regression fitting on the basis of single factor experiments under the actions of three factors of different feed-liquid ratios, different extraction times and different extraction temperatures, and confirms the optimal extraction conditions, and the regression model prediction is reliable and stable.
In the purification process, the experiment adopts a graphitized carbon black and amino mixed filler solid phase extraction glass column, and compared with graphitized carbon black and PSA (N-propyl-ethylenediamine) columns used in the prior art, PSA and amino have similar selectivity, but the PSA polarity is weaker than the amino, and the extracted target PAEs are weak or medium in polarity. In the purification process, according to the principle of similar compatibility, compared with PSA, amino groups are less likely to retain target PAEs, so that the amino groups are relatively easier to collect in effluent, and the extraction rate is improved.
Drawings
FIG. 1 is a gas chromatograph-mass spectrometer total ion flow chromatogram (0.05. Mu.g/mL) of 5 phthalate compound standard solutions;
FIG. 2 is a graph showing the relationship between the extraction temperature and the amount of PAEs extracted from tea leaves after single-factor analysis and ultrasound;
FIG. 3 is a graph showing the relationship between the extraction time and the amount of PAEs extracted from tea leaves after single-factor analysis and ultrasound;
FIG. 4 is a graph showing the relationship between the single factor analysis of different feed to liquid ratios and the extraction of PAEs in tea;
FIG. 5 is a three-dimensional response surface plot of the interaction between feed to liquid ratio and post-ultrasound extraction time;
FIG. 6 is a three-dimensional response surface plot of the interaction between post-ultrasound extraction temperature and post-ultrasound extraction time;
FIG. 7 is a three-dimensional response surface plot of the interaction between feed to liquid ratio and post-ultrasonic extraction temperature.
Detailed Description
The invention is further described below with reference to the drawings and examples of the specification.
Example 15 preparation of PAEs Standard working curves
1.1 Preparation of PAEs Standard solution
Preparing mixed standard stock solution: accurately sucking DMP, DEP, DIBP, DBP and DEHP standard samples, placing the samples into a 100mL volumetric flask, and accurately fixing the volume to the scale by using n-hexane to prepare 1 mug/mL mixed standard solution. Mixing standard stock solution, and storing at-20deg.C.
Preparing a matrix standard working solution: the mixed standard stock solution is taken and diluted step by using a blank sample extracting solution to prepare a matrix standard working solution with the concentration of 0 mug/mL, 0.001 mug/mL, 0.005 mug/mL, 0.01 mug/mL, 0.02 mug/mL, 0.05 mug/mL, 0.1 mug/mL, 0.2 mug/mL, 0.5 mug/mL and 1 mug/mL, and the matrix standard working solution is used for making a standard working curve and is prepared on-the-fly.
TABLE 15 information on phthalate Compounds
1.2 Detection parameters of gas chromatograph-mass spectrometer
The instrument was Agilent GC-MS (Agilent 6890A GC-MS D6975). The chromatographic column is an HP-5MS quartz capillary column (30.0mX1250 μm X0.25 μm), sample injection is not carried out in a split mode, the flow is constant, the flow is 1.0mL/min, the solvent delay is 5min, the temperature of a sample injection port is 280 ℃, and the temperature rise program is as follows: the initial temperature is 80 ℃, kept for 1min, and is raised to 140 ℃ at 6 ℃/min, kept for 2min, and is raised to 150 ℃ at 2 ℃/min, kept for 2min, and is raised to 180 ℃ at 5 ℃/min, kept for 1min, and is raised to 250 ℃ at 6 ℃/min, kept for 1min, and is raised to 270 ℃ at 3 ℃/min, and kept for 1min at 270 ℃. EI ion source with ionization energy of 70eV, using selective ion scan, carrier gas was 99.999% high purity helium gas, ion source temperature 230 ℃.
1.3 Preparation of standard curve
And (3) injecting a standard working solution into a gas chromatograph-mass spectrometer (GC-MS), measuring the chromatographic peak area of the corresponding phthalate, and drawing a standard working curve by taking the mass concentration of the standard working solution as an abscissa and the peak area of the quantitative ion of each phthalate compound as an ordinate.
1.4 Mass spectrum information of 5 phthalate compounds
The ion scan mode (SIM) was selected for scanning the characteristic fragment ions of the target, the peak time of 5 pae compounds was determined, the retention time, qualitative ion and quantitative ion of the target analyte were shown in table 2, and the total ion flow chromatogram of 5 pae compounds was shown in fig. 1.
TABLE 2 quantitative and qualitative Selective ion tables for phthalate Compounds
1.5 Detection limit, quantitative limit, linear relation and precision detection result of 5 phthalate compound standard substances
The quantitative Limit (LOQ) and the detection Limit (LOD) are calculated by 10 times of signal-to-noise ratio and 3 times of signal-to-noise ratio respectively, the quantitative limit of 5 PAEs compounds is 2-3 mug/kg, the detection limit is 0.6-0.9 mug/kg, and the sensitivity meets the detection requirement. The prepared standard working solution is selected to have low, medium and high gradient concentration of 3, GC-MS detection is carried out, each gradient is measured for 6 times in parallel, the relative deviation (RSD) is calculated according to the measured peak area, and the precision of 5 PAEs is obtained (n=6). The results show that the linearity of 5 PAEs is between 0.001-1 mug/mL (except DBP is 0.001-0.5 mug/mL), R 2 >0.9910, linearity is good, RSD is 0.6% -5.2%, both are less than 6%, and instrument precision is good (Table 3).
Table 35 regression equation, correlation coefficient, detection limit and quantitative limit of phthalate compounds
Example 2 response surface method-based optimization of extraction method of PAEs in tea
2.1 Method for extracting PAEs from tea sample
10G of tea samples are crushed and placed in a hard whole glass vessel for standby. Accurately weighing 2.0g of crushed and uniformly mixed tea leaf sample (accurate to 0.0001 g) into a 40mL glass centrifuge tube, adding 2g of sodium chloride, adding 20mL of normal hexane, fully homogenizing the solution by using a vortex oscillator, performing ultrasonic extraction for 3 hours at 40 ℃, standing and extracting for 12 hours at 40 ℃, centrifuging for 2 minutes at 3000r/min at 10 ℃ by using a refrigerated centrifuge, and collecting supernatant. Adding 20mL of n-hexane into the lower layer residue, shaking and mixing, centrifuging at 10deg.C for 2min at 3000r/min, collecting supernatant, and mixing the two supernatants. The supernatant was distilled to near dryness under reduced pressure in a 40 ℃ water bath, and 8mL of acetonitrile was added: toluene (3:1) solution was dissolved and purified by SPE cartridge (solid phase extraction cartridge model CARB/NH2, 1000mg/6mL, available from Di Ma technology Co.). To the column was added 10mL acetonitrile: activating toluene (3:1) solution, and discarding effluent liquid; adding the liquid to be purified into a column, and collecting effluent liquid; 22mL of acetonitrile-toluene (3:1) solution was added to the column, the effluent was collected, and the two collected effluents were combined; the collected effluent was distilled to dryness under reduced pressure in a 40 ℃ water bath, cooled, 1mL of n-hexane was added, and mixed well for GC-MS analysis. GC-MS parameter settings refer to example 1.
2.2 Optimization design of PAEs extraction condition response surface of tea sample
Based on the extraction method, three factors of different feed-liquid ratios (1:10, 1:15,1:20,1:25, 1:30), different extraction times after ultrasonic treatment (3 h,6h,9h,12h,18h,24 h) and different extraction temperatures after ultrasonic treatment (20 ℃,30 ℃,40 ℃,50 ℃,60 ℃) are set, and single-factor tests are carried out, wherein each test is repeated for 3 times. Based on a single factor test, taking the feed liquid ratio (A), the post-ultrasonic extraction temperature (B) and the post-ultrasonic extraction time (C) as response surface test independent variables, taking the extraction quantity (R) of the PAEs in the tea as a response value, performing Box-Behnken optimization treatment by using Design-ExertV8.0.6, and determining the optimal extraction condition of the PAEs in the tea by variance analysis and response contour map analysis, and predicting the response according to the optimal condition.
2.3 Analysis of Single factor test results
As shown in figure 2, with the increase of the ultrasonic post-extraction temperature, the extraction amount of PAEs in the tea leaves is in a trend of rising and then falling, and the detected extraction amount of PAEs reaches the highest when the ultrasonic post-extraction temperature is 40 ℃.
As shown in figure 3, with the increase of the post-ultrasonic extraction time, the PAEs extraction amount in the tea leaves is in a trend of rising and then falling, and the detected PAEs extraction amount is highest when the post-ultrasonic extraction time is 12 hours.
As shown in FIG. 4, under the condition that the feed liquid ratio is 1:20, the detected PAEs extraction amount reaches the highest.
2.4 Response surface optimization test result analysis
2.4.1 Response surface test design and results
Based on a single factor experiment, the feed-liquid ratio (A), the post-ultrasonic extraction temperature (B) and the post-ultrasonic extraction time (C) are selected as independent variables according to the center combination design principle of Box-Behnken, the PAEs extraction amount is a response value, 3-factor 3 horizontal response surface analysis is adopted, the influence of interaction among factors on the PAEs extraction amount of tea is mainly considered, and the design scheme and the result of the response surface experiment are shown in Table 4.
TABLE 4 response surface test design and test results
2.4.2 Model fitting and significance analysis
Multiple regression fitting is carried out on the test model by using Design-ExertV8.0.6 software, and multiple regression equations of PAEs extraction amount and feed liquid ratio (A), ultrasonic post-extraction temperature (B) and ultrasonic post-extraction time (C) in the tea are as follows:
Y＝567.92-17.28A+28.44B+107.34C-10.93AB-8.77AC+4.24BC-158.79A2-1
37.54B2-140.13*C2。
TABLE 5 analysis of regression coefficient significance and analysis of variance of model
Regression coefficient significance analysis and model variance analysis as shown in table 5. The model P <0.05 and the mismatch term P >0.05 show that the model has obvious regression and the mismatch term is not obvious, which indicates that no mismatch factor exists, and the regression equation can be used for analyzing the experimental result. The correction coefficient of the model R 2 adj = 0.9202, which means that the model has only a 7.98% variation, which can be explained by the model. The correlation coefficient R 2 = 0.9651, the difference between the predicted R 2＝0.7364,R2 and R 2 adj is less than 0.1, the difference between the R 2 adj and the predicted R 2 is less than 0.2, the signal to noise ratio AdeqPrecision =11.872 >4, the parameters fully illustrate that the model is obvious, the fitting degree is higher, the experimental prediction error is small, the data repeatability is good, and the influence of 3 factors on PAEs extraction can be better reflected. Factors C, A 2、B2 and C 2 both appear to be very significant (P < 0.05). The size sequence of the influence of 3 factors on the content of the extracted PAEs is as follows: c > B > A.
2.4.3 Response surface analysis of factor interactions
The response surface graph is a three-dimensional space curved surface graph formed by the PAEs extraction amount in the tea and each influencing factor, the interaction between the optimal value point and each parameter can be reflected, and the steeper the curve is, the larger the influence of the factors on the PAEs extraction amount in the tea is. The 3D response graph (figures 5-7) of the influence of the interaction of the feed liquid ratio, the ultrasonic post-extraction temperature and the ultrasonic post-extraction time on the extraction amount of the PAEs of the tea leaves shows that the influence of the ultrasonic post-extraction time on the extraction of the PAEs is the largest, the influence of the ultrasonic post-extraction temperature is the next smallest, and the influence of the feed liquid ratio is the smallest. The interaction effect of the liquid-to-liquid ratio and the post-ultrasonic extraction temperature is larger, and the interaction effect of the liquid-to-liquid ratio and the post-ultrasonic extraction time is the least obvious.
And calculating and predicting a quadratic regression equation according to the analysis result of the response surface, wherein the optimal conditions for extracting PAEs in the tea are that the feed-liquid ratio is 1:20, the post-ultrasonic extraction temperature is 40 ℃, and the post-ultrasonic extraction time is 12 hours. Under these conditions the theoretical predicted content is 585.85. Mu.g/kg. 3 groups of parallel experiments are carried out according to the optimal extraction conditions, the average value of the PAEs content is 574.50 mug/kg, the relative error is 1.98%, and the regression model prediction is reliable and stable.
Example 3 method verification
3.1 Labelling recovery test
Based on the linear range of 5 PAEs compounds and the dilution of the pretreatment of the samples, mixed standard solutions of 100, 500 and 1000 mug/L were added to the blank tea samples, and 3 groups of parallel samples were tested for each gradient, and the results are shown in Table 5. The recovery rate of the 5 PAEs compounds is 80.70% -98.68%, the Relative Standard Deviation (RSD) of the 5 PAEs compounds is 2.7% -8.1%, the recovery rates are all less than 10%, and the method has good precision.
3.2 Matrix Effect investigation
The prepared mixed standard solution is diluted into standard working solutions with 5 gradient concentrations by normal hexane and tea blank matrix solution (pretreated by the method of the example 2), and GC-MS detection is carried out to obtain the standard curve slope of 5 PAEs compounds in the normal hexane and tea blank matrix solution. The Matrix Effect (%) =b/a×100, where a is the slope of the solvent standard curve and B is the slope of the Matrix standard curve, compared using the relative response method. The matrix effect of 5 pae compounds in the tea matrix was calculated (table 6). The results show that the matrix effect of 5 PAEs compounds is 0.4-1.1, and the interference of the matrix on the compounds is small.
Table 65 labeled recovery of PAEs in tea
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.
Claims (2)
1. The method for extracting and detecting main PAEs in tea based on response surface optimization is characterized by comprising the following steps of:
1) Establishing a tea sample PAEs extraction flow
The PAEs extraction flow is as follows: adding normal hexane into a tea sample to be detected according to a certain feed liquid ratio, and performing ultrasonic extraction, wherein the ultrasonic is performed for 3 hours at 40 ℃; standing the extract at a certain temperature for a certain time, concentrating by reduced pressure distillation, and purifying and eluting by solid phase extraction; the solid phase extraction column adopted by the solid phase extraction is a graphitized carbon black and amino mixed filler solid phase extraction glass column; the solid phase extraction column is activated by adopting acetonitrile and toluene mixed solution with the volume ratio of 3:1, and is eluted by adopting acetonitrile and toluene mixed solution with the volume ratio of 3:1;
2) Optimization of PAEs (polycyclic aromatic hydrocarbon) extraction condition response surface of tea sample
Setting three factors of different feed-liquid ratios, different extraction standing time after ultrasonic treatment and different extraction standing temperature after ultrasonic treatment, and performing a single factor test; based on a single factor test, taking the feed liquid ratio, the post-ultrasonic extraction standing temperature and the post-ultrasonic extraction standing time as response surface test independent variables, taking the extraction quantity of PAEs in the tea as a response value, performing Box-Behnken optimization treatment, and determining the optimal extraction condition of the PAEs in the tea through variance analysis and response contour map analysis;
in the optimal extraction condition of PAEs in the obtained tea, the feed liquid ratio of the tea sample to the normal hexane is 1:20; after ultrasonic treatment, standing at 40 ℃ for 12 h;
3) Extraction and detection of main PAEs in tea
For a tea sample to be detected, extracting PAEs by adopting the extraction flow of the step 1) under the optimal extraction conditions of the PAEs in the tea obtained in the step 2), detecting the PAEs by using a gas chromatograph-mass spectrometer, and calculating according to the standard working curve of each phthalate compound to obtain the detection content;
In the step 3), eluent obtained through solid phase extraction and purification is distilled to dryness under reduced pressure, cooled, n-hexane is added, and then gas chromatography-mass spectrometer detection is carried out;
the gas chromatography conditions were: the chromatographic column is an HP-5MS quartz capillary column with the size of 30.0m multiplied by 250 mm multiplied by 0.25 mm; the temperature of the sample inlet is 280 ℃; sample introduction without diversion; the sample injection amount is 1mL; the carrier gas is high-purity helium, the constant flow rate is 1.0mL/min; the temperature program is as follows: the initial temperature is 80 ℃, kept for 1min, and is raised to 140 ℃ at 6 ℃/min for 2min, and is raised to 150 ℃ at 2 ℃/min for 2min, and is raised to 180 ℃ at 5 ℃/min for 1min, and is raised to 250 ℃ at 6 ℃/min for 1min, and is raised to 270 ℃ at 3 ℃/min for 1min;
the mass spectrum conditions are as follows: the ionization mode is electron bombardment ionization source; ionization energy is 70eV; the temperature of the transmission line is 280 ℃; the ion source temperature is 230 ℃; delaying the solvent for 5min; the detection mode is selected ion scanning.
2. The method according to claim 1, wherein in step 2), the optimum extraction conditions of PAEs in tea leaves are determined by variance analysis and response contour map analysis, specifically:
The response surface graph is a three-dimensional space curved surface graph formed by the PAEs extraction amount in the tea and each influence factor, and the steeper the curve is, the larger the influence of the influence factors on the PAEs extraction amount in the tea is; performing multiple regression fitting by using Design-ExertV8.0.6 software, and establishing a multiple regression equation of PAEs extraction amount and feed liquid ratio in tea, post-ultrasonic extraction standing temperature and post-ultrasonic extraction standing time;
And obtaining the optimal extraction condition of the PAEs in the tea according to a quadratic regression equation.
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