Simultaneous determination of multiclass plant growth regulators in fruits using the quick, easy, cheap, effective, rugged, and safe method and ultra-high performance liquid chromatography-tandem mass spectrometry

In this study, a modified quick, easy, cheap, effective, rugged, and safe method combined with ultra-high performance liquid chromatography and tandem mass spectrometry was developed for the multiclass determination of 28 plant growth regulators in various fruits. Different extraction solvents and adsorbents, including primary secondary amine, octadecylsilyl, graphitized carbon black, and zirconia-based sorbent, were investigated. Internal calibration and isotope internal standards, chlormequat chloride-d(4), mepiquat chloride-d(6), indole-3-acetic acid-d(2), and forchlorfenuron-d(5) were used to improve accuracy. For method validation, good linearity, low limits of detection and quantification were obtained. At three spiked concentrations (10, 50, and 100 mu g/kg), satisfactory recoveries with relative standard deviations of 2.4-17.5% were obtained for strawberries (75.2-119.8%), grapes (70.5-114.0%), tangerines (71.7-115.4%), apples (72.7-115.4%), and kiwi fruits (71.7-119.2%). Samples analysis revealed that 15.6% of the samples (n = 96) were contaminated with one or two kinds of plant growth regulators, including chlormequat chloride, forchlorfenuron, paclobutrazol, 2,4-dichlorophenoxyacetic acid, 2-diethylaminoethyl hexanoate, and mepiquat chloride. Similar results were obtained by ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry, indicating the robustness, effectiveness, and suitability of the developed method for routine monitoring of plant growth regulator residues in fruits.