Simultaneous Determination of Residues of 23 Plant Growth Regulators in Codonopsis Radix and Angelica Sinensis by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

After the sample was dried, crushed, and sieved, an aliquot (3.0 g) was taken, and 5 mL of 1.0% (volume fraction) glacial acetic acid solution was added to completely immerse the sample by vortex. After soaking for 30 min, 15 mL of acetonitrile was added, and the mixture was shaken vigorously for 10 min. Then 4.0 g of anhydrous magnesium sulfate (AMS) and 1.0 g of sodium chloride were added, and the mixture was shaken vigorously to prevent salt agglomeration, shaken vigorously for another 10 min, and centrifuged for 10 min. All the supernatant was collected, and blown to near dryness by nitrogen at 40℃, and the residue was dissolved in 1 mL of 50% (volume fraction) acetonitrile solution. The obtained solution was introduced into the ultra-high performance liquid chromatograph-tandem mass spectrometer, and the targets were separated on the Waters AQUITY UPLC BEH Shield RP18 chromatographic column by gradient elution with mixed solutions composed of 0.05% (volume fraction, the same below) formic acid solution containing 5 mmol·L^-1 ammonium formate and acetonitrile solution containing 5 mmol·L^-1 ammonium formate and 0.05% formic acid at different volume ratios, and ionized by the ESI⁺ and ESI^- modes, detected by the sMRM mode, and quantified by matrix matching method. It was shown that linear relationships between values of the mass concentration and the corresponding peak area of 23 plant growth regulators were kept in definite ranges, with lower limits of determination (10S/N) in the range of 0.2-3.0 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 75.2%-109%, and RSDs (n=5) of the determined values ranged from 1.8% to 13%. The proposed method was used for the analysis of 46 batches of Codonopsis Radix and 30 batches of Angelica sinensis samples. Among them, detection amounts of sodium 4-nitrophenol in 10.9% of Codonopsis Radix samples and 6.7% of Angelica sinensis samples exceeded the limit (100 μg·kg^-1) specified in GB 2763-2021.