Abstract: A novel method was established for the determination of six plant growth regulators (PGRs), 2,4-dichlorophenoxy acetic (2,4-D), 4-chlorophenoxy-acetic acid (CAP), 4-(3-indolyl)-butyric acid (BAA), forchlorfenuron (CPPU), abscisic acid (ABA) and trans-zeatin (ZT) in strawberry using liquid chromatography-quadrupole-time of flight mass spectrometry (LC-Q TOF MS). The Quick, Easy, Cheap, Effective, Rugged and Safe method (QuEChERS) has been validated for the extraction. In this QuEChERS method, the sample was extracted by acetonitrile and cleaned up with C18 adsorbent. The extract was measured directly by LC-Q TOF MS with electrospray ionization in negative mode. The compounds were separated on an Eclipse XDB-C8 column (150 mm×4.6 mm, 5 μm) with acetonitrile-5 mmol/L ammonium acetate-0.1% formic acid as mobile phase under gradient elution. The confirmatory analysis was carried out by determining the accurate masses of all compounds and fragment ions upon Target MS/MS. The limits of detection (LODs) were between 1 μg/kg and 5 μg/kg. The linear range was 0.005~1.0 mg/L for each analyte. The recoveries ranged from 87% to 107% with the relative standard deviations (RSDs) less than 10% (n=6). The method was proved to be simple and accurate.

Key words: plant growth regulators, strawberry, liquid chromatography-quadrupole-time of flight mass spectrometry (LC-Q TOF MS)