LC-MS Determination of Glyphosate, Glyphosinate, and AMPA in Green Team using a Supel^™ Carbon LC Column and QuEChERS Cleanup with Supel^™ QuE Verde

Waters^® Acquity I-class plus and Waterswa^® Xevo TQS UPS with electrospray ion source (ESI source)

Supel^™ Carbon LC, 2.7 μm, 10 cm × 2.1 mm I.D. (59986-U)

[A] 20mM Ammonium carbonate (pH=9)
[B] Acetonitrile:water (95:5, v:v)

0-1 min 100% to 95% A; 1 -3 min 95 to 0% A; 3-13 min 0% A, 13-13.1 0 to 95% A, 13.1-15 min 95% A

0.30 mL/min

30 °C

MSD, ESI-, MRM: Glufosinate180.0 to 63.0 (quantitative); AMPA 110.0 to 63.0 (quantitative); Glyphosate 168.0 to 63.0 (quantitative)

5.0 μL

Green tea sample spiked at 50 µg/kg: 2 g sample extracted with 20.0 mL of a mixture of acetonitrile/water (40:60, v:v), vortexed at 3500 rpm for 2 min, ultrasonic extraction for 30 min and centrifuge at 10000 rpm for 5 min. 2.0 mL of the extract added to a 15 mL Supel^™ QuE Verde (55442-U) tube, vortexed for 3 min at 2500 rpm, centrifuged for 3 min at 10,000 rpm and filtered using a 0.22 μm syringe filter.

Glyphosate is a broad-spectrum herbicide with toxicity similar to organophosphorus compounds and is one of the most frequently used herbicides in the world. Furthermore, the chemicals’ usage increased after the introduction of genetically modified, glyphosate-tolerant crops such as corn, soybeans, and cotton. In many regions of the world such as the USA, Europe, and China limit values in food samples are defined by official institutions such as the EPA and the European Commission to ensure consumer health.

A U/HPLC-MS/MS method combined with solvent extraction and QuEChERS purification was established to determine glyphosate, glyfosinate, and AMPA residues in green/fresh tea and results compared to criteria stated in Chinese official methods. The samples were purified using a Supel^™ QuE Verde adsorbent mix for green sample matrices and analysed by LC-MS using a Supel^™ Carbon LC UHPLC column with porous graphitic carbon (PGC) particles that enabled RP conditions. Note: It is recommended to prime the column with a range of sample matrix extract injections (20-50). Samples were quantified against an external standard calibration method. The results showed linear responses in the range of 1.0 to 150 μg/L for the injected solution with correlation coefficients (R²) greater than 0.998 for all three analytes. The observed recoveries were ranging from 81.0% to 107%, and the precision (RSD) was 2.7-5.0%. Therefore, linearity, RSD, and recovery rate were meeting the Chinese GB 23200.13-2016 method criteria. The determined sensitivities for LODs (µg/kg): glyphosate: 5.0; glufosinate: 9.0; AMPA:11.0; and for LOQ (µg/kg): glyphosate: 15.0; glufosinate: 27.0; AMPA:33.0. These meet or exceed the criteria of the SN/T 1923-2007 method. An inter-lab comparison showed reproducibility meeting the criteria of GB/T 27404-2008. These results confirm the accuracy and reliability of the method for the detection and analysis of glyphosate, glufosinate, and AMPA in green tea.

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