Comparison of QuEChERS for Multi-Residue of Pesticides inVegetable & Grain

Introduction

Pesticide residues are one of the most common threatsto food safety. QuEChERS effectively separate tracepesticide residues in vegetables, fruits, grains andother matrices. QuEChERS is capable of effectivelyseparating trace pesticide residues in various matricessuch as vegetables and grains.

This experiment compared the purification efficiencyand recovery rate of different matrices (simple matrix:cabbage, complex matrix: chives, grain: corn flour)between Copure® QuEChERS and well-known Brand A’sQuEChERS kits. As result, regardless of the matrix type,Copure® QuEChERS achieves equivalent to the Brand A.

Experiment

Extraction and purification of vegetable

Weigh 10.000 g of the ground sample (simple matrix:cabbage, complex matrix: chives) into a 50 mLcentrifuge tube. Add 10 mL of acetonitrile and vortex for1 min. Then add QuEChERS extraction salt (Copure®:COQ050010H, Brand A: #1). Shake vigorously for 1 min,then vortex for 5 min. Centrifuge at 4000 r/min for 5 min.Transfer 6 mL of the upper acetonitrile layer to 15 mLtubes (cabbage: Copure®: COQ015022H, Brand A: #2;chives: Copure®: COQ015020H, Brand A: #3). Vortex for1 min and centrifuge at 4000 r/min for 5 min. Preciselypipette 2 mL of the supernatant to a clean tube andevaporate to nearly dryness at 40 °C in a water bath.Dilute to 1 mL with the initial mobile phase and vortexto mix well. After filter by 0.22 μm nylon membrane, thesample is ready for analysis.

Extraction and purification of grain

Weigh 5.00 g of corn flour into a 50 mL centrifugetube. Add 10 mL of water, and vortex to mix well. Letit stand for 30 min. Add 15 mL of acetonitrile-aceticacid solution (99+1), and vortex for 5 min. Extract byultrasonic treatment for 10 min. Then add QuEChERSextraction salt (Copure ®: COQ050020H, Brand A:#4). Shake vigorously for 1 min, and vortex for 5 min.Centrifuge at 4000 r/min for 5 min. Transfer 6 mL ofthe upper acetonitrile layer to a 15 mL tube (Copure®:COQ015033H, Brand A: #5). Vortex for 5 min andcentrifuge at 4000 r/min for 5 min. Precisely pipette 2mL of the supernatant to a clean tube and evaporate tonearly dryness at 40 °C. Dilute to 1 mL with the initial mobile phase and vortex to mix well. After filter by 0.22μm nylon membrane, the sample is ready for analysis.

Preparation of Standard Curve Solution

Prepare blank sample in the same procedures.Add mixed standard solution and add dilute to theconcentration for LC-MS determination.

Instrumental Conditions

1.Chromatographic conditions

Instrument: Thermo Fisher TSQ Endura

Chromatographic column: Hypersil GOLD C18 (2.1mm×100 mm, 1.9 μm)

Mobile phase: A: 0.1 % Formic acid water, B: MethanolFlow rate: 0.4 mL/min

Column temperature: 35 ℃

Injection volume: 5 μL

Table 1. Gradient Elution Program