QuEChERS-Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry for Determination of Five Currently Used Herbicides

A simple, rapid, sensitive and accurate ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method was developed for the simultaneous determination of five currently used herbicides in soil. The sample preparation using the modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method completed the extraction and clean-up steps in one procedure. In this none buffer QuEChERS method, samples were extracted with acetonitrile, cleaned up with primary secondary amine (PSA) and C18 sorbent and then centrifugated and filtrated before detection. The UPLC-MS/MS method was performed on Waters ACQUITY UPLC™ BEH C18 (50 mm × 2.1 mm i.d., 1.7 μm) at a column temperature of 30 °C, with the gradient elution with methanol and pure water as the mobile phase at a flow rate of 0.25 mL min−1. The positive electrospray ionization (ESI+) source under the multiple reaction monitoring (MRM) mode and external standard method were used for quantification. The linear range was shown to be from 0.5 to 200 μg L−1 with a correlation coefficient of 0.9984. The limits of detection (LOD) were in the range of 0.005–0.020 μg kg−1 (S/N = 3) and the limits of quantification (LOQ) were in the range 0.017–0.067 μg kg−1 (S/N = 10). The method was validated with soil samples spiked at two fortification levels (4 and 40 μg kg−1) and recoveries were in the range 75.4%–98.5% with relative standard deviations (RSD) of 3.2%–11.8%.