Determination method for residues of dioctyl phenyl polyglycol ether in fruits, vegetables and tea

Abstract

The present invention discloses a method for determining the residue of iprobenfos in fruits, vegetables and tea. The sample is extracted with an aqueous solution of 25±2% acetone containing 1±0.02% formic acid. After centrifugation and dilution, without solid-phase extraction and purification, using the dication adduct ion of guazatine [M+2H]<supgt;2+< / supgt; as the parent ion, liquid chromatography-tandem mass spectrometry determination is carried out; plastic vessels are used throughout the determination process. The present invention uses oranges, tangerines, oranges, apples, watermelons, grapes, tomatoes, cucumbers, tea, etc. as analysis samples, extracts the sample with an aqueous solution of 25±2% acetone (containing 1±0.02% formic acid), without solid-phase extraction and purification, using the dication adduct ion of guazatine [M+2H]<supgt;2+< / supgt; as the parent ion, and establishes an ultra-high performance liquid chromatography-tandem mass spectrometry method for determining the residue of iprobenfos in fruits, vegetables and tea. Plastic vessels are used throughout the determination process, which is sensitive, accurate, precise and temperature-resistant. The method detection limit is 2 μg / kg, and the quantification limit is 4 μg / kg, and trace analysis of iprobenfos in fruits, vegetables and tea can be realized.

Description

Technical Field

[0001] The present invention relates to a method for determining the residue of iminoctadine tris(albesilate) in fruits, vegetables and tea, belonging to the technical field of determining the residue of iminoctadine tris(albesilate) in fruits, vegetables and tea. Background Art

[0002] Iminoctadine tris(albesilate), trade name Bayer CropScience, is a contact and preventive fungicide and preservative, which can inhibit spore germination, germ tube elongation, appressorium and hypha formation, and can control fungal diseases caused by most ascomycetes and deuteromycetes. It is widely used in the disease control and preservation of fruits and vegetables such as citrus, tomato and tea. Especially in China, as a major country in fruit production and consumption, with the largest cultivation area and output in the world, in order to cope with the diseases and rots during the storage and transportation of fruits, the use of fungicides for preservation has become a common phenomenon.

[0003] GB 2763-2021 "National Food Safety Standard Maximum Residue Limits of Pesticides in Foods" stipulates that the maximum residue limit of iminoctadine tris(albesilate) in various fruits, vegetables and tea is 0.2-3 mg / kg. However, due to the lack of corresponding national standard detection methods, the monitoring of the residue of iminoctadine tris(albesilate) in fruits, vegetables and tea has become a blind spot, and the risk assessment work cannot be carried out. At present, there are few reports on the detection methods for the residue of iminoctadine tris(albesilate). Among them, the liquid chromatography method has low sensitivity and serious matrix interference, and it is difficult to meet the requirements of the current relevant limit standards; the liquid chromatography-tandem mass spectrometry method uses the single-charge adduct ion [M+H] of iminoctadine + as the parent ion, resulting in low sensitivity of the method. Summary of the Invention

[0004] The present invention provides a method for determining the residue of iminoctadine tris(albesilate) in fruits, vegetables and tea. Using oranges, tangerines, oranges, apples, watermelons, grapes, tomatoes, cucumbers, tea, etc. as analysis samples, the sample is extracted with an acetone aqueous solution of 25±2% (containing 1±0.02% formic acid) without solid-phase extraction and purification. Using the double-charge adduct ion [M+2H] of iminoctadine 2+ as the parent ion, an ultra-high performance liquid chromatography-tandem mass spectrometry method for determining the residue of iminoctadine tris(albesilate) in fruits, vegetables and tea is established. Plastic vessels are used throughout the determination process to ensure test stability, sensitivity, accuracy and precision, especially suitable for trace analysis of iminoctadine tris(albesilate).

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A method for determining the residue of bis (trioctylphenyl) sulfonate in fruits, vegetables and tea leaves. The sample is extracted with an aqueous solution of 25±2% acetone containing 1±0.02% formic acid. After centrifugation and dilution, it is determined by liquid chromatography-tandem mass spectrometry without solid-phase extraction purification, using the double-charged adduct ion of guazatine [M+2H] 2+ as the parent ion. Throughout the determination process, plastic vessels are used.

[0007] In this application, "%" refers to volume percentage unless otherwise specified.

[0008] An aqueous solution of 25±2% acetone containing 1±0.02% formic acid means that in an aqueous solution of acetone with a volume concentration of 25±2%, there is formic acid with a volume content of 1±0.02%, hereinafter expressed as 25±2% aqueous acetone solution (containing 1±0.02% formic acid). The same meaning applies to the following similar expressions.

[0009] Through the selection of the extraction agent of 25±2% aqueous acetone solution (containing 1±0.02% formic acid) in this application, the pretreatment is simplified. Only one centrifugation step is required, and solid-phase extraction column purification is not needed, which saves time and effort, is simple and fast, and has a high recovery rate.

[0010] In this application, the liquid chromatography-tandem mass spectrometry method using the double-charged adduct ion of guazatine [M+2H] 2+ as the parent ion greatly improves the response value and sensitivity of the method, and is more suitable for the trace analysis of bis (trioctylphenyl) sulfonate.

[0011] The inventor also unexpectedly found in the experiment that bis (trioctylphenyl) sulfonate has an adsorption interaction with the glass surface, resulting in a significant decrease in the response value over time. To ensure the test stability, plastic utensils must be used throughout the sample pretreatment and injection analysis process.

[0012] The test object of this application is fruits, vegetables and tea leaves. The tea is Liubao tea, and the fruits and vegetables include fruits and vegetables.

[0013] To improve the stability and recovery rate, the reagent used for dilution is an aqueous solution of 50±2% methanol containing 0.5±0.02% formic acid. The selection of the aforementioned dilution reagent effectively improves the stability and recovery rate.

[0014] To improve the sensitivity and accuracy, as one specific implementation scheme, the method for determining the residue of bis (trioctylphenyl) sulfonate in fruits, vegetables and tea leaves includes the following steps:

[0015] 1) Mix the sample with an aqueous solution of 25±2% acetone containing 1±0.02% formic acid, oscillate and extract ultrasonically. After centrifugation at low temperature and high speed, the supernatant is diluted 9-11 times with an aqueous solution of 50±2% methanol containing 0.5±0.02% formic acid, filtered through a membrane, and placed in a plastic sample bottle.

[0016] 2) Perform liquid chromatography-tandem mass spectrometry determination;

[0017] Among them, the liquid chromatography conditions are as follows: using a 2.6 μm Biphenyl chromatographic column (100×3.0 mm) as the analytical column, and gradient elution with a mobile phase of an aqueous solution of 5±0.02 mmol / L ammonium formate containing 0.1±0.02% formic acid and a methanol solution of 0.1±0.01% formic acid; the mass spectrometry conditions are as follows: under the positive ion mode multiple reaction monitoring mode of an electrospray ionization source (ESI), using the double-charge adduct ion m / z: 178.7 [M+2H] of dodine 2+ as the parent ion, and forming an MRM ion pair with its daughter ions m / z: 157.8, 187.3, and 280.5 for detection; quantitative analysis is performed by matrix-matched external standard method.

[0018] In order to facilitate obtaining a clear extract, in step 1), during low-temperature high-speed centrifugation, the temperature is 2-5°C and the speed is 6000-9000 r / min.

[0019] In the above step 1), before dilution and passing through the membrane, at 2-5°C, centrifuge at 10000-13000 r / min for 3-5 min.

[0020] In the above step 1), passing through the membrane means passing through a 0.22 μm filter membrane; the dosage of an aqueous solution of 25±2% acetone containing 1±0.02% formic acid is 0.8-1.2 mL per g of sample.

[0021] In order to improve the response, in step 2), the column temperature of the analytical column is 40±2°C.

[0022] Using the method of this application, the linear relationship of dodine in fruits, vegetables and tea is very good in the range of 0.1 ng / mL to 100.0 ng / mL, and the correlation coefficient r is greater than 0.9995. The linear relationship of this method is good, significantly better than the prior art.

[0023] Using the method of this application, for dodine in fruits, vegetables and tea in the range of 0.1 ng / mL to 100.0 ng / mL, the linear regression equation is y=(1250-2800)x±(1-142), where y is the chromatographic peak area and x is the concentration of dodine.

[0024] Preferably, the plastic ware is PP (polypropylene) or PE (polyethylene); the tea is Liubao tea, and the fruits and vegetables are tangerines, oranges, oranges, apples, watermelons, grapes, tomatoes and cucumbers. For others, this method can be referred to.

[0025] For technologies not mentioned in the present invention, refer to the prior art.

[0026] The method for determining the residue of dioctyl phenyl sulfonate in fruits, vegetables and tea leaves of the present invention has high sensitivity, accuracy, precision and reproducibility, is simple, rapid and stable. The detection limit of the method is 2 μg / kg, and the quantification limit is 4 μg / kg, which is more suitable for the trace analysis of dioctyl phenyl sulfonate; it meets the requirements of GB / T 27404-2008 "Laboratory Quality Control Specification for Food Physical and Chemical Detection", fills the gap in the national relevant detection methods, and provides a method basis for monitoring the residue of dioctyl phenyl sulfonate in fruits, vegetables and tea leaves and risk assessment. Description of the Drawings

[0027] Figure 1 is the multiple reaction monitoring (MRM) chromatogram of the dioctyl phenyl sulfonate standard solution (10 ng / mL) (the chromatographic column is 2.6 μm Biphenyl chromatographic column (100×3.0 mm), the daughter ion m / z in Figure a: 157.8, the daughter ion m / z in Figure b: 187.3, the daughter ion m / z in Figure c: 280.5); Detailed Embodiments

[0028] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments only.

[0029] The instruments used in each example are as follows:

[0030] API4000+ ultra-high performance liquid chromatography-tandem mass spectrometry, ESI ion source, AB SCIEX Company, USA;

[0031] 2.6 μm Biphenyl chromatographic column, 100×3.0 mm;

[0032] Vortex mixer, talboys Company, USA;

[0033] KQ-500DE ultrasonic cleaner, Kunshan Ultrasonic Instrument Co., Ltd.;

[0034] KH20R-II high-speed refrigerated centrifuge, Hunan Kaida Scientific Instrument Co., Ltd.;

[0035] HY-4 oscillator, Guohua Electric Appliance Co., Ltd.;

[0036] All utensils are made of plastic;

[0037] The reagents used are as follows:

[0038] Biguanide trioctylbenzene sulfonate standard solution in methanol, No. ZB-233184-1mL, concentration 100μg / mL, CAS No.: 169202-06-6, Shanghai Zhenzhun Biotechnology Co., Ltd.;

[0039] Chromatographic grade methanol, acetone, acetonitrile (Fisher Scientific); chromatographic grade formic acid, acetic acid (CNW); chromatographic grade ammonium formate (MREDA); sodium acetate, concentrated ammonia (analytical grade, Tianjin Zhiyuan Chemical Reagent Co., Ltd.);

[0040] PRIME HLB Plus Short (335 mg) column (Waters, USA); QuEChERS reagent purification tube (5982-5256, Agilent, USA); 0.2 μm microporous filter membrane (Pall Corporation); 1.5 mL PP short thread micro transparent sample bottle (Shimadzu, Japan).

[0041] Samples: 3 batches of tea, 3 batches of mandarin oranges, 5 batches of tangerines, 3 batches of oranges, 1 batch each of apples, watermelons, grapes, tomatoes and cucumbers, totaling 19 batches of samples. Tea was purchased from the tea market in Liubao Town, Guangxi, and fruits and vegetables were purchased from the Donglingnan Street Farmers' Market in Nanguan District, Changchun City, Jilin Province.

[0042] Before testing, prepare fruit, vegetable and tea samples in accordance with the requirements of GB 2763-2021 and weigh the required amount.

[0043] Example 1

[0044] Determination of biguanide trioctylbenzene sulfonate residues in fruits, vegetables and tea, including:

[0045] 1) Sample processing:

[0046] Weigh 10.0 g of the sample (accurate to 0.01 g) into a 50 mL plastic centrifuge tube with a stopper, add 10 mL of 25% acetone aqueous solution (containing 1% formic acid), vortex (2500 rpm) for 2 min, oscillate (300 rpm) for 30 min, ultrasonicate (600 W, 40 kHz) for 10 min, centrifuge at 9000 r / min for 5 min (4°C), take 5 mL of the supernatant, centrifuge the supernatant at 9000 r / min for 5 min (4°C), take 1.0 mL of the supernatant into a 10 mL plastic volumetric flask, add 50% methanol aqueous solution (containing 0.5% formic acid) to make the volume 10 mL (diluted 10 times), mix well, take 1.0 mL of the dilution into a 1.5 mL plastic centrifuge tube, centrifuge at 13000 r / min for 5 min (4°C), pass the supernatant through a 0.22 μm filter membrane into a plastic sample bottle, and perform liquid chromatography-tandem mass spectrometry determination.

[0047] 2) Liquid chromatography - tandem mass spectrometry conditions:

[0048] Liquid chromatography conditions: 2.6μm Biphenyl Chromatographic column (100×3.0mm); Mobile phase: Pump A is 5mmol / L ammonium formate solution (containing 0.1% (v / v) formic acid), Pump B is 0.1% (v / v) formic acid - methanol, gradient elution program for Pump B: 0min 5%; 1.0min, 40%; 6.0min, 85%; 7.0min, 95%; 9.0min, 95%; 9.1min, 5%; 12.0min, 5%. Column temperature 40°C; Flow rate: 0.4mL / min; Injection volume: 5μL.

[0049] Mass spectrometry conditions: Ion source: ESI; Scanning mode: positive ion mode multiple reaction monitoring (+MRM), using the double - charged adduct ion of dodine m / z: 178.7 [M + 2H] 2+ as the parent ion, and forming MRM ion pairs with its daughter ions m / z: 157.8, 187.3, 280.5 for detection, and quantitative analysis by matrix - matched external standard method; Ion source parameters: Electrospray voltage (IS): 5500V; Nebulizing gas pressure (GS1): 413700Pa; Auxiliary gas pressure (GS2): 413700Pa; Curtain gas pressure (CUR): 206850Pa; Ion source temperature (TEM): 550°C; Collision - activated dissociation gas (CAD): 7mL / min. The monitored ion pairs, collision gas energy, and declustering voltage parameters are shown in Table 1.

[0050] Table 1 Monitored ion pairs, collision gas energy, and declustering voltage parameters

[0051]

[0052] Note: The "*" ion is used for quantification.

[0053] Preparation of matrix standard solution

[0054] Weigh a blank sample with the same properties as the sample to be measured, and prepare a blank sample matrix solution according to the method described in the above "Sample treatment". Gradually dilute the 100μg / mL standard solution of dodecylbenzenesulfonic acid tris - octylammonium salt with the blank matrix solution to prepare matrix standard solutions with concentrations of 10ng / mL, 100ng / mL, and 200ng / mL respectively.

[0055] Respectively pipette 10 μL, 50 μL of 10 ng / mL matrix standard solution and 10 μL, 20 μL, 50 μL, 100 μL, 200 μL, 500 μL, 1000 μL of 100 ng / mL matrix standard solution into 9 1.5 mL plastic centrifuge tubes. Then, make up the volume to 1.0 mL with the matching blank matrix solution respectively, mix well, and centrifuge at 13000 r / min for 5 min. The supernatant is filtered through a 0.22 μm filter membrane into 9 plastic sample bottles respectively. The concentrations of the prepared matrix-matched standard working solutions are 0.1 ng / mL, 0.5 ng / mL, 1.0 ng / mL, 2.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 20.0 ng / mL, 50.0 ng / mL, 100.0 ng / mL respectively.

[0056] Quantification method

[0057] Quantitative analysis is carried out by matrix external standard method through drawing a matrix standard curve. The test results are calculated as dodine, and converted into the content of dodine according to the ratio of the molecular weight of dodine to the molecular weight of triton B-207.

[0058] Matrix effect is the main reason affecting the sensitivity and accuracy of liquid chromatography-tandem mass spectrometry. It is caused by the competition between the sample matrix and the target compound during the ionization of the sample solution, and is divided into matrix enhancement effect and matrix suppression effect. The matrix effect (ME) is evaluated by calculating the recovery rates of each concentration point in the matrix standard solution through the solvent standard curve. When ME is within 85% - 115%, it indicates that the matrix effect is not significant and the influence of the matrix can be ignored. The results show (see Table 2): Triton B-207 shows different degrees of matrix suppression effect in matrix samples such as citrus reticulata blanco, apple, watermelon, grape, tomato, cucumber, tea, etc. Among them, the average matrix effects in citrus reticulata blanco and apple samples are 83.7% and 82.7% respectively, which are weak matrix suppression effects; the average matrix effects in watermelon and tomato samples are 57.3% and 47.4% respectively, which are extremely strong matrix suppression effects; the average matrix effect in grape sample is 73.1%, which is a strong matrix suppression effect; the average matrix effects in cucumber and tea samples are 87.2% and 93.3% respectively, and the matrix effects are not significant. To correct the matrix suppression effect, matrix-matched external standard method is used for quantification.

[0059] Table 2 Matrix effect evaluation

[0060]

[0061] Calibration curve and detection limit

[0062] According to the above method, the matrix standard working solution series of wogan, apple, watermelon, grape, tomato, cucumber, and tea were determined respectively. Taking the concentration of the analyte in the matrix-matched standard solution as the abscissa and the chromatographic peak area of the product ion for quantitative determination of the analyte as the ordinate, the matrix-matched standard working curve was plotted. The regression equation and correlation coefficient are shown in Table 3. The results showed that in the matrices of wogan, apple, watermelon, grape, tomato, cucumber, and tea, there was a good linear relationship for bis(tricyclohexyltin) oxide in the range of 0.1 - 100 ng / mL, and the correlation coefficient r was greater than 0.9995. In addition, low-concentration bis(tricyclohexyltin) oxide standard solutions were added to blank wogan, apple, watermelon, grape, tomato, cucumber, and tea samples respectively to prepare spiked samples. The samples were extracted and determined according to the above method, and the signal-to-noise ratio was calculated. The spiked amount corresponding to 3 times the signal-to-noise ratio (S / N = 3) was taken as the detection limit; the spiked amount corresponding to 10 times the signal-to-noise ratio (S / N = 10) was taken as the quantification limit. Results: The detection limit of bis(tricyclohexyltin) oxide by this method was 2 μg / kg, and the quantification limit was 4 μg / kg.

[0063] Table 3 Regression analysis of matrix calibration curve, method detection limit and quantification limit

[0064]

[0065]

[0066] Note: y - peak area, x - concentration.

[0067] Precision and spiked recovery

[0068] Commercially available samples of citrus fruits, oranges, apples, watermelons, grapes, tomatoes, cucumbers, and tea were randomly selected. A 1 μg / mL standard solution of bis (trioctylphenyl) sulfonate (prepared with a solvent of 25% acetone and 0.5% formic acid) was added at 7 concentration levels to prepare spiked samples. Each addition level was measured 6 times, and the spike recovery rate and relative standard deviation were calculated. The data are shown in Table 4. The results indicate that the recovery rate of bis (trioctylphenyl) sulfonate in citrus fruits ranges from 89.4% to 103.2%, and the relative standard deviation is between 2.3% and 6.5%; in oranges, the recovery rate ranges from 90.6% to 104.3%, and the relative standard deviation is between 3.8% and 6.1%; in apples, the recovery rate ranges from 91.2% to 96.0%, and the relative standard deviation is between 1.9% and 6.2%; in watermelons, the recovery rate ranges from 91.7% to 105.7%, and the relative standard deviation is between 1.3% and 6.6%; in grapes, the recovery rate ranges from 91.2% to 94.5%, and the relative standard deviation is between 1.7% and 6.8%; in tomatoes, the recovery rate ranges from 98.0% to 104.7%, and the relative standard deviation is between 3.7% and 6.6%; in cucumbers, the recovery rate ranges from 92.7% to 96.9%, and the relative standard deviation is between 1.5% and 4.9%; in tea, the recovery rate ranges from 92.1% to 96.7%, and the relative standard deviation is between 2.2% and 5.1%. These results meet the requirements for precision and recovery rate in Appendix F of GB / T 27404—2008 "Laboratory Quality Control Code for Physical and Chemical Testing of Foods", indicating that this method is accurate, stable, and reliable (Table 4).

[0069] Table 4 Precision and Recovery Rate Determination Results (n = 6)

[0070]

[0071]

[0072] μg / kg, μg is the spiked amount, kg is the sample amount;

[0073] Sample Determination

[0074] Three batches of randomly selected commercially available tea, three batches of wogan oranges, five batches of mandarin oranges, three batches of oranges, and one batch each of apples, watermelons, grapes, tomatoes, and cucumbers, a total of 19 batches of samples, were tested according to the above method. Results: Iprodione was detected in all three batches of wogan oranges, and the contents were 42.0 μg / kg, 37.8 μg / kg, and 22.0 μg / kg respectively; Iprodione was detected in two of the five batches of mandarin oranges, and the contents were 21.2 μg / kg and 6.5 μg / kg respectively; Iprodione was detected in one of the three batches of oranges, and the content was 1.8 μg / kg; No iprodione was detected in the apple, watermelon, grape, tomato, cucumber, and tea samples. The detection rate of iprodione in citrus fruits was 54.5%, indicating that iprodione is commonly used as an antiseptic and fresh-keeping agent in citrus fruits, but its residue is far lower than the national standard limit requirement of 3 mg / kg, and all are qualified products.

[0075] In the following comparative examples, those not specifically described refer to Example 1

[0076] Comparative Example 1

[0077] Comparison of adduct ions:

[0078] According to the chemical property of the structure of iprodione having multiple charge centers, the iprodione detected by mass spectrometry can generate [M+H] + , [M+2H] 2+ , [M+3H] 3+ and other adduct ions. By injecting a 200 ng / mL iprodione standard solution through a syringe pump, the [M+H] + , [M+2H] 2+ , [M+3H] 3+ of iprodione were collected. For each form of adduct ion, the daughter ions with high response values were selected to form ion pairs respectively, and the mass spectrometry parameters such as the collision gas energy CE and the declustering voltage DP were further optimized by Ramp. The online liquid chromatograph was used to inject and analyze the 200 ng / mL standard solution to verify the response value and stability of the selected ion pairs. The results are shown in Table 5. From the data in Table 5, it can be seen that for each pair of ion pairs calculated according to the daughter ion with the highest response value, taking the double-charge adduct ion [M+2H] 2+ as the parent ion, the response value of its daughter ion is 1.8 times that of the triple-charge adduct ion [M+3H] 3+ and 6.2 times that of the single-charge adduct ion [M+H] + , exceeding the expected effect. Therefore, the ion pair formed with the double-charge adduct ion [M+2H] 2+ as the parent ion in this application is used as the monitoring ion pair for this experiment.

[0079] Comparison of Mass Spectrometry Parameters and Response Values of Different Forms of Adduct Ions

[0080]

[0081] Comparative Example 2

[0082] Comparison of mobile phases:

[0083] Using 2.6μm Biphenyl Chromatographic column (100×3.0mm) for separation, using four mobile phase systems of 0.1% formic acid in water - 0.1% formic acid in acetonitrile, 0.1% formic acid in water - 0.1% formic acid in methanol, 5 mmol / L ammonium formate solution (containing 0.1% formic acid) - 0.1% formic acid in acetonitrile, and 5 mmol / L ammonium formate solution (containing 0.1% formic acid) - 0.1% formic acid in methanol respectively, and detecting and analyzing the standard working solution with a concentration of 10 ng / mL according to the gradient elution conditions in Table 1 to investigate the effects of the mobile phase on the peak time, peak shape and response value of dodine. The results show that when using 0.1% formic acid in water - 0.1% formic acid in acetonitrile and 0.1% formic acid in water - 0.1% formic acid in methanol as the mobile phase, the chromatographic peaks have serious tailing and low response values; after adding 5 mmol / L ammonium formate to the mobile phase, sharp and symmetric chromatographic peaks can be obtained, and the response value is twice that of the mobile phase without ammonium formate; when using 5 mmol / L ammonium formate solution (containing 0.1% formic acid) - 0.1% formic acid in acetonitrile as the mobile phase, the peak time of the dodine chromatographic peak is 1.94 min, which is relatively early, while when using 5 mmol / L ammonium formate solution (containing 0.1% formic acid) - 0.1% formic acid in methanol as the mobile phase, the peak time of the chromatographic peak is 2.37 min, which is relatively moderate. Therefore, in this application, 5 mmol / L ammonium formate solution (containing 0.1% formic acid) - 0.1% formic acid in methanol is used as the mobile phase.

[0084] Comparative Example 3

[0085] Comparison of chromatographic columns:

[0086] Compare 2.6μm Biphenyl Chromatographic column (100×3.0mm) and 2.6μm F5 The effects of two chromatographic columns, namely chromatographic column (100×3.0mm) and chromatographic column (50×3.0mm), on the separation of the dodine chromatographic peak. The results show that on the 2.6μm Biphenyl Chromatographic column (100×3.0mm), both the peak time, peak shape and response value are better than the latter. See the multiple reaction monitoring (MRM) chromatogram of the dodine tris(octylphenyl) sulfonate standard solution in Figure 1.

[0087] Comparative Example 4

[0088] Comparison of Vessel Materials and Dilution Solvents

[0089] Using a glass sample vial to hold a 100 ng / mL standard solution of bis(trioctyl) sulfonium bis(trifluoromethylsulfonyl)imide (prepared with a 20% methanol and 0.1% formic acid solution), and performing injection analysis, it was found that the response value of bis(octyl)amine could only remain stable within 2 hours, after which its response value began to decrease, and after 4 hours, the measured response value was 27% - 33% of the original value.

[0090] Still using a glass sample vial, the difference is that: changing to a 50% methanol and 5 mmol / L ammonium formate solution (containing 0.1% formic acid) to prepare the standard solution for injection analysis, the response value of bis(octyl)amine could also only remain stable within 3 hours, and after 5 hours, the measured response value decreased to 56% of the original value, indicating that by changing the solvent for preparing the standard solution, the stability of the response value of bis(octyl)amine cannot be completely improved to meet the detection requirements.

[0091] Still using a glass sample vial, the difference is that: changing to a 50% methanol aqueous solution (containing 0.5% formic acid) to prepare the standard solution for injection analysis, the response value of bis(octyl)amine could also only remain stable within 5 hours, and after 5 hours, the measured response value decreased to 62% of the original value. It shows that the adsorption of the glass bottle is very strong, and the 50% methanol solution (containing 0.5% formic acid) will delay its adsorption period, but it will also be gradually adsorbed after more than 5 hours.

[0092] Changing to a 1.5 ml PP short-threaded micro transparent sample vial to hold the standard solution, and performing injection analysis on the standard solutions prepared with a 50% methanol solution (containing 0.5% formic acid) and a 50% methanol solution (containing 0.1% formic acid) respectively. Results: Using the 50% methanol solution (containing 0.5% formic acid), the response value of bis(octyl)amine could remain stable within 3 days, and the response values were all maintained above 96% of the original value; using the 50% methanol solution (containing 0.1% formic acid), the response value of bis(octyl)amine could remain stable within 2 days, and after 3 days, the measured response value was 88% of the original value. It is proved that the glass material injection vial has an adsorption effect on bis(trioctyl) sulfonium bis(trifluoromethylsulfonyl)imide, and the decrease in the response value of bis(octyl)amine is indeed caused by the adsorption on the surface of the glass sample vial. At the same time, it shows that formic acid above 0.5% can effectively reduce adsorption. Therefore, plastic material vessels should be used throughout the entire process of standard solution preparation, sample pretreatment, and injection analysis in this application.

[0093] Comparative Example 5

[0094] Comparison of Extraction Methods

[0095] Respectively selecting 0.1% formic acid - acetonitrile, 0.1% formic acid - methanol, acetonitrile, and methanol as extraction agents, ultrasonically extracting the fortified sample of wogan (fortification amount 100 μg / kg), after vortexing and centrifuging, taking the supernatant and passing it through Purify with a PRIME HLB PlusShort(335mg) column or QuEChERS reagent (containing 147.7mg PSA, 15.1mg GCB, 887.2mg magnesium sulfate). Then, take the purified solution, dilute and mix it in a 1:1 ratio before injecting it for analysis. The recovery rate ranges from 2.7% to 11.3%, indicating that this extraction and purification method is not advisable.

[0096] Instead, use 0.5% formic acid - methanol, 1% acetic acid - acetonitrile, 1% ammonia - acetonitrile, 50% methanol solution (containing 0.5% formic acid), 0.2mol / L sodium acetate buffer solution (pH5.2), and 25% acetone aqueous solution (containing 0.5% formic acid) as extraction agents respectively. After ultrasonic and oscillating extraction, without passing through a purification column, use multiple low - temperature and high - speed centrifugations for purification, and then dilute the sample solution by 10 times before injecting it for analysis. The results show (see Table 6): Only the recovery rate of using 25% acetone aqueous solution (containing 0.5% formic acid) as the extraction agent reaches 80%, and the recovery rates of the other 5 extraction agents are all lower than 60%. This indicates that methanol, 50% methanol solution, acidified or ammoniated acetonitrile, and sodium acetate buffer solution have a low extraction rate for bis - guanidine tri - octyl benzene sulfonate. In this application, the acetone - formic acid solution system is used as the extraction solution.

[0097] Table 6 Recovery rates of different extraction solvents

[0098]

[0099] Comparison of extraction solvents

[0100] Weigh 5g of fortified ponkan samples (fortification amount 100μg / kg), add 10mL of extraction solvents (acetone and formic acid contents are as listed in Table 7) respectively, and perform sample pretreatment according to the method described in "Sample treatment" of Example 1. The results show (see Table 7): The recovery rates of extraction agents with 1% formic acid content are significantly higher than those with 0.5% formic acid content; The changes in recovery rates with acetone contents of 0%, 5%, 10%, and 15% are not obvious, and the recovery rates of 20% acetone solution (containing 1% formic acid) and 25% acetone solution (containing 1% formic acid) extraction agents are significantly increased. The experiment also found that when the acetone content in the extraction agent reaches 20% and above, a clear extraction sample solution can be obtained, which is beneficial to subsequent experimental operations; The recovery rate of the extraction agent with 30% acetone content decreases and the repeatability of detection data is poor. Therefore, this application selects 25% acetone solution (containing 1% formic acid) as the extraction solvent.

[0101] Table 7 Influence of extraction agents with different acetone and formic acid contents on recovery rates

[0102]

[0103] Comparative Example 6

[0104] Comparison of centrifuge speed and temperature

[0105] Extract the spiked Wogan sample (spiking amount: 100 μg / kg) with 25% aqueous acetone solution (containing 1% formic acid), and centrifuge at 5000 r / min and 9000 r / min at 10 °C and 4 °C respectively. Results: Centrifuging at 9000 r / min at 4 °C makes it easier for the sample solution to stratify and obtain a clear extract.

[0106] Comparison of dilution solvents

[0107] Select 0.5% formic acid in methanol, 50% aqueous methanol solution (containing 0.5% formic acid), and 0.5% formic acid in water as dilution solvents respectively, and dilute the sample solution by 10 times for injection analysis. The results show (see Table 8): Using 50% methanol solution (containing 0.5% formic acid) as the dilution solvent, the recovery rate is the highest; using 0.5% formic acid in methanol as the diluent, the recovery rate is the lowest and solvent effect occurs in the chromatographic peaks. Therefore, this application selects 50% aqueous methanol solution (containing 0.5% formic acid) as the sample solution dilution solvent.

[0108] Table 8 Effects of different dilution solvents on recovery rate

[0109]

Claims

1. A method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea, characterized in that: The sample was extracted with an aqueous solution of 25±2% acetone containing 1±0.02% formic acid. After centrifugation and dilution, it was determined by liquid chromatography-tandem mass spectrometry without solid-phase extraction purification, using the dication adduct ion of guazatine 2+ as the parent ion. Plastic vessels were used throughout the determination process; The reagent used for dilution is an aqueous solution of 50±2% methanol containing 0.5±0.02% formic acid; Liquid chromatography conditions: Using a Kinetex R 2.6 μm Biphenyl 100 Å chromatographic column as the analytical column; Mobile phase A pump is an aqueous solution of 5 ± 0.02 mmol / L ammonium formate containing 0.1 ± 0.02% formic acid, and mobile phase B pump is a methanol solution of 0.1 ± 0.01% formic acid. Gradient elution program for pump B: 5% at 0 min; 40% at 1.0 min; 6.0 min, 85%; 7.0 min, 95%; 9.0 min, 95%; 9.1 min, 5%; 12.0 min, 5%; Mass spectrometry conditions: Under the positive ion mode of the electrospray ionization source in the multiple reaction monitoring mode, using the double-charged adduct ion of dodine m / z : 178.7 [M+2H] 2+ as the parent ion, and forming an MRM ion pair with its daughter ions m / z : 157.8, 187.3, 280.5 for detection.

2. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to claim 1, characterized in that: It includes the following steps: 1) The sample is mixed with an aqueous solution of 25±2% acetone containing 1±0.02% formic acid. After shaking and ultrasonic extraction, it is centrifuged at low temperature and high speed. The supernatant is diluted 9 - 11 times with an aqueous solution of 50±2% methanol containing 0.5±0.02% formic acid, then filtered through a membrane and placed in a plastic sample bottle; 2) Liquid chromatography - tandem mass spectrometry determination is carried out; quantitative analysis is performed by matrix - matched external standard method.

3. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to claim 2, wherein: In step 1), during low - temperature and high - speed centrifugation, the temperature is 2 - 5°C and the speed is 6000 - 9000 r / min.

4. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to claim 2, wherein: In step 1), before filtration after dilution, it is centrifuged at 10000 - 13000 r / min for 3 - 5 min at 2 - 5°C.

5. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to claim 2, wherein: In step 1), the membrane filtration is through a 0.22 - μm filter membrane; the dosage of the aqueous solution of 25±2% acetone containing 1±0.02% formic acid is 0.8 - 1.2 mL per gram of sample.

6. The method for determining the residue of dioctyl phenyl polyglycol ether in fruits, vegetables and tea leaves according to claim 2, wherein: In step 2), the column temperature of the analytical column is 40±2°C.

7. The method for determining the residue of dioctyl phenyl polyglycol ether in fruits, vegetables and tea leaves according to any one of claims 1-5, characterized in that: The linear relationship of bis - guanidine tri - octyl benzene sulfonate in fruits, vegetables and tea leaves is in the range of 0.1 ng / mL to 100.0 ng / mL, and the correlation coefficient r is greater than 0.9995.

8. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to claim 7, wherein: The linear regression equation for biguanide trioctylbenzene sulfonate in the range of 0.1ng / mL to 100.0ng / mL is: y =(1250~2800) x ±(1~142), y is the chromatographic peak area, x is the concentration of biguanide trioctylbenzene sulfonate.

9. The method for determining the residue of dioctyl phenyl polyglycol sulfonate in fruits, vegetables and tea leaves according to any one of claims 1-5, characterized in that: The plastic ware is made of PP or PE; the tea is Liubao tea, and the fruits and vegetables are tangerines, oranges, oranges, apples, watermelons, grapes, tomatoes and cucumbers.

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