Analysis of Plant Growth Substances (Auxins, Gibberelins and Cytokinins) in Vegetables Using High-Performance Liquid Chromatography Coupled to Electrospray Ionization Tandem Mass Spectrometry

Abstract

This study was applied to extract and analyze major plant growth substances in vegetables. Plant tissues was washed by tap water before frozen in liquid nitrogen and kept under 4oC in the freeze until to be analyzed. After grinding into powder, plant hormones in the samples were extracted by 2-propanol/H2O/concentrated HCl (2:1:0.002, vol/vol/vol) and Dichloromethane (CH2Cl2), respectively. The extract was concentrated by nitrogen flow during an hour and analytes were dissolved in MeOH and then directly injected into column and analyzed by HPLC-ESI-MS/MS.9 types of plant growth substances belong to auxin, gibberellin and cytokinin, including: Gibberelin A3 (GA3), Gibberelin A4 (GA4), Gibberelin A7 (GA7), Indole-3-butyric acid (IBA), Indole-3-carboxylic acid (ICA), Trans-zeatin (tZ), N6-Benzyladenine (BA), Kinetin (K) and N6-Isopentenyladenine (iP) had identified and quantified in the plant tissues. The method showed good linearity for all 9 analytes with regression coefficients R2> 0.996. Limit of detection ranged from 0.19 ng.g-1 to 1.20 ng.g-1 for cytokinins (BA, tZ, K and iP), from 2.06 ng.g-1 to 3.22 ng.g-1 for auxins (ICA and IBA), and from 4.14 to 5.16 ng.g-1 for gibberellins (GA3, GA4 and GA7). The mean recoveries for all of the analytes were from 83.38 to 104.50%and the repeatability standard deviation of the recovery for hormones in three different concentrations as low, medium and high levels was from 0.22% to 11.07%. To our knowledge, this is a rapid, simple, sensitive, accurate and efficient method for analysis plant growth substances in vegetables as well as the first study analyzing 9 plant hormones: GA3, GA4, GA7, IBA, ICA, tZ, BA, K and iP in plant tissues using high-performance liquid chromatography equipped with an electrospray ionization tandem mass spectrometry. This plays a pivotal role in studying, determining and quantifying residues of plant growth substances that accumulate in agricultural products in general and green vegetables in particular. Since then, helping national managers have appropriate measures for using plant growth regulators in the production of agricultural products as well as recommending to consumers know which products are at risk of many plant growth stimulants and potentially affecting human health.