Determination of Five plant growth regulator residues in leafy vegetables by QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry

A method for the simultaneous determination of low-polarity pesticide, such as forchlorfenuron, paclobutrazol, uniconazole and propiconazole, and high polarity pesticide, such as chlormequat chloride in leafy vegetables was developed using QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Vegetable samples were extracted by acetonitrile containing 1% (V%) acetic acid. Then they were cleaned up by GCB and PSA adsorbents before separated on a C18 column and detected under positive polarity multiple reactions monitoring (MRM) mode. The matrix-matched external standard calibration curves were used for quantitative analysis. The linearity of 5 plant growth regulators was in the range of 1-1 000 μg/L, with correlation coefficients higher than 0.999 3. The limits of detection (LOD) of the proposed method were 0.002 to 0.04 μg/kg. The limit of quantification (LOQ) was 0.01 mg/kg which was the lowest spiked concentration. Recoveries at three spiked levels of 0.01, 0.1 and 0.5 mg/kg ranged from 71% to 93% with relative standard deviations (RSDs) from 0.2% to 10% in flowering Chinese cabbage, Chinese kale and pak-choi. The presented method is fast, simple and accurate, which can meet the requirements for the determination of residues of forchlorfenuron, paclobutrazol, uniconazole, propiconazole and chlormequat chloride in leafy vegetables.