Simultaneous Determination of Seven Plant Growth Regulators in Melons and Fruits by Modified QuEChERS Coupled with Capillary Electrophoresis

A capillary electrophoresis method for the simultaneous determination of seven plant growth regulators including gibberellic acid, abscisic acid, 3-indole acetic acid, 3-indolepropionic acid, 3-indolebutyric acid, 2,4-dichlorophenoxyacetic acid, and 2-methyl-4-chlorophenoxyacetic acid in melons and fruits was established and validated. The samples were ultrasonically extracted with acidified acetonitrile and then dehydrated. The resulting solution was purified with modified QuEChERS method, and then dried-up under weak nitrogen flow, and the residue was redissolved with methanol-water (1:4, v/v) as sample solution. The electrophoretic separation was performed in an uncoated fused-silica capillary with borax buffer (pH 10.5) containing 29% of ethanol as the running buffer. The running voltage was 25 kV with the column temperature of 30 °C. The linear ranges of gibberellic acid, abscisic acid, and 2-methyl-4-chlorophenoxyacetic acid were from 0.10 to 8.0 μg/mL, while the others were from 0.05 to 4.0 μg/mL with the correlation coefficients greater than 0.997. The limits of detection and the limits of quantification of the method were in the range of 1.54–5.76 and 5.12–19.2 μg/kg, respectively. The recoveries of the method ranged from 69.0 to 109% with the relative standard deviations ranging from 2.01 to 15.4%. The proposed method has been successfully applied to the determination of plant growth regulator residues in 15 melon and fruit samples, and gibberellic acid and abscisic acid were detected in the samples.