Development of a screening method for twelve plant growth regulator residues in green tea by ultra performance liquid chromatography-high resolution mass spectrometry

A screening method was established for the determination of twelve plant growth regulators (PGRs) in green tea using ultra performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS), including 2,4-dichlorophenoxy acetic (2,4-D), 4-chlorophenoxy-acetic acid (4-CPA), 4-(3-indolyl) -butyric acid (IAA), forchlorfenuron (CPPU) and 4-indoly-3-ylbutyric acid (IBA), etc. The extract was measured directly by UPLC-HRMS with electrospray ionization in both positive and negative modes. The analytes were separated on CAPCELL PKA-C18 column (100 mm×2.1 mm, 2 μm) with gradient elution．In the positive mode, the mobile phase was methanol-water containing 5 mmol/L ammonium acetate and 0.1% formic acid, while, in the negative mode, methanol-water was used as the mobile phase. The confirmation analysis was based on accurate mass measurement of all compounds (scan mode) and their fragment ions, retention times (RTs) and isotopic patterns (target MS/MS mode). The report limits (RLs) of twelve plant growth regulators were validated as 0.01 mg/kg. At 0.01, 0.1 and 0.5 mg/kg spiked levels, the recoveries and the relative standard deviations (RSDs) were 61%-130% and 1.8%-17%, respectively. This method was simple, quick, and can be applied as a screening method for PGRs detection in green tea.