Application of TSQ 8000 Evo for rapid detection of various pesticide residues in the Hong Kong "Pesticide Residues Regulations"

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Deng Wujian 1 Zhu Manjie 1 Wu Fengqi 2 Wu Weidong 2
1. Thermo Fisher Scientific 2 Shenzhen Entry-Exit Inspection and Quarantine Bureau
Key words: Residue regulations for pesticides in food; QuEChERS; pesticide residues; TSQ 8000 Evo triple quadrupole GC/MS
1. Foreword
As early as June 2012, the Hong Kong Legislative Council had completed the review of the Procedures for the Residues of Pesticides in Food Regulations (Cap 132CM) (the Regulations). The relevant regulations were officially implemented on August 1, 2014. The Residues in Pesticides Regulations on Foods sets out the maximum allowable levels of pesticide residues in certain foods and some interpretation provisions. They are the regulations and policies that must be followed for vegetable projects in Hong Kong. The Hong Kong Pesticide Residues in Food Regulation contains 360 pesticides and a maximum residue/maximum residue limit of more than 7,000 “pesticide-food” combinations. More than 95% of the compounds are detected by GC/MS/MS and LC/MS/MS as pesticides included in the Hong Kong Regulations.
This experiment used the Thermo ScientificTM TSQ 8000 Evo in combination with the Thermo Fisher Scientific Peptide Analysis Column (TR-Pesticide II 30 m*0.25 mm*0.25 μm) to analyze 101 pesticide residues in the Hong Kong Regulations, which was excellent. result. The minimum detection limit of various pesticides is between 0.07-2.69 μg/L, and there is good linearity in the range of 5-200 μg/L, and 6 samples are injected continuously with 10 μg/L sample to obtain RSD at 1.51-9.3. Between %, this method shows good reproducibility.
2. Experimental part
2.1 Instruments and reagents
Mass Spectrometry Instruments: Thermo ScientificTM TSQ 8000 Evo Mass Spectrometer (Thermo Fisher Scientific, USA);
Gas Chromatograph: Thermo ScientificTM Trace 1310 GC with AI l310 Autosampler (Thermo Fisher Scientific, USA);
Column: TR-Pesticide II 30m*0.25mm*0.25 μm capillary column;
Reagents: acetone, acetonitrile: chromatographically pure;
2.2 Instrument method
Gas phase method:
Column oven: 40 min at 40 oC, raised to 90 oC at 25 oC/min for 1.5 min, then raised to 180 oC at 25 oC/min, raised to 280 oC at 5 oC/min, and finally at 10 °C / Min Heat up to 300 °C for 5 min. Inlet: splitless injection, no split time: 1.5 min; inlet temperature: 270 oC; carrier gas: constant flow, 1.2 mL/min; transmission line: 300 oC mass spectrometry: ion source temperature 300 oC, using Acquisition-Timed method, SRM scan, specific detection ion pairs are shown in Table 1:
Table 1: List of test compounds and SRM ion pair information
2.3 sample preparation
1) Sample preparation: Take an appropriate amount of vegetable sample in a homogenizer, crush the vegetable sample, and homogenize and mix.
2) Sample extraction: Weigh 10 g sample into 50 mL QuEChERS extraction tube, add 10 mL acetonitrile and mix well, add 4 g MgSO4, 1 g NaCl, 1 g anhydrous trisodium citrate and 0.5 g disodium citrate. Shake for 2 minutes on a vortex shaker, place on a parallel shaker for 30 minutes, then centrifuge at 5000 rpm for 5 min.
3) Sample Purification: The supernatant was removed and transferred to a 15 mL QuEChERS purification tube containing 1200 mg MgSO4, 400 mg PSA and 400 mg C18. The sample was vortexed for 1 min and then centrifuged at 5000 rpm for 5 min. Take 1 mL of the supernatant into the injection vial and analyze by GC-MS/MS.
2.4 sample matrix solution
The cabbage sample was processed according to the procedure of 2.3 to obtain a matrix solution of the blank sample.
2.5 standard solution configuration
1) Standard stock solution: Weigh 10 mg of each pesticide single standard compound on one hundred thousandth of an analytical balance, add 10 mL of the corresponding solvent (add acetone, toluene or acetonitrile according to different compounds) to prepare a concentration of A solution of about 1000 mg/L. The concentration of each individual standard stock solution was calculated based on the amount of sample and the volume of solvent added. All single-label stock solutions were stored frozen in a -20 °C freezer. The single standard stock solution is valid for 6 months.
2) Mixing standard intermediate solution: Pipette an appropriate amount of single standard stock solution and dilute with acetonitrile. The concentration of the intermediate standard stock solution was 10.0 mg/mL. The intermediate standard stock solution was stored frozen in a -20 °C freezer. The intermediate stock is valid for 3 months.
3) Working standard solution: Take appropriate amount of mixed standard intermediate solution, and sequentially dilute to a working standard solution with concentrations of 5.0, 10.0, 20.0, 50.0, 100.0 and 200.0 μg/L with blank sample substrate solution (2.4).
3. Analysis of results
3.1 chromatographic separation results
Each compound SRM mass spectrometry condition (parent ion-subion-collision energy) is derived from TraceFinder's CDB (see Table 1), and the SRM chromatogram of the target is obtained by running the sample under this condition as shown in Figure 1.
Figure 1: Standard solution chromatogram (200 μg/L)
3.2 Minimum detection limit of the method
The minimum detection limit is calculated by S/N=3, and the results are shown in Table 2. Figure 2 shows a chromatogram of a portion of the 1 μg/L pesticide. It can be seen that the detection limit of pesticide residues is basically less than 1.0 μg/L, which is sufficient to meet the requirements of current national standards and international pesticide detection methods, and to ensure the qualitative and quantitative detection of pesticides in samples.
Figure 2: Chromatogram of 1 μg/L partial pesticide
3.3 standard curve linearity, detection limit and precision
The mixed standard solutions were prepared at the concentrations of 5.0, 10.0, 20.0, 50.0, 100.0, and 200.0 μg/L, respectively, by the above methods, and the linearity of each component was examined. The experimental results showed that the linearity of 101 pesticide components in 5.0-200.0 μg/L was good, and the linear correlation coefficient was greater than 0.99 (see Table 2). The same sample was continuously injected with 6 needles, and the RSD was between 1.51 and 9.3%. Good sex. The detection limits of each component were calculated according to the IUPAC method. The detection limits of each component ranged from 0.07 to 2.69 μg/L (see Table 2), which basically satisfied the current method for pesticide residue analysis (detection limit 10 μg/L) ) requirements.
Table 2: Retention Time, Linearity, and RSD% Statistics
4 Conclusion
In this paper, QuEChERS pretreatment-gas-phase tandem mass spectrometry (QuEChERS–GC-MS/MS) was used to determine 101 pesticide residues in vegetable matrices. Sample preparation can be completed in 60 min without complicated manual pretreatment. The fast QuEChERS pre-treatment combined with Thermo Fisher's TSQ 8000 Evo triple quadrupole instrument provides a highly sensitive, accurate and easy-to-use solution for pesticide residue analysis. All in all, the complete workflow solution provided by Thermo Fisher Scientific, together with the newly developed TSQ 8000 GC-MS/MS system, provides good system performance for multi-residue analysis and accurate quantification.
Acknowledgement
Special thanks to the Shenzhen Entry-Exit Inspection and Quarantine Bureau for providing test samples and compound mixed standards to complete this application article.

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