Determination of Plant Growth Regulators in Chinese Herbal Medicine: A Comparison of Liquid (QuEChERS) and Solid (MSPD) Extraction Methods

This work aimed to compare the methods for the determination of twenty plant growth regulators (PGRs) from Chinese herbal medicines by applying liquid and solid extraction methods simultaneously. Quick, easy, cheap, effective, rugged and safe (QuEChERS) and matrix solid-phase dispersion (MSPD) were chosen as the liquid and solid extraction methods, respectively. Due to the complex matrix of herbal medicine, carbon nanotubes were selected as the solutions/sorbents for the extraction and purification. The extracts were analyzed by ultra-performance liquid chromatography-triple quadrupole-mass spectrometry (UPLC-MS/MS). Both methods resulted in good efficiency for the extraction and purification. The recoveries fell in the range of 71-117% with relative standard deviations (RSDs) less than 19%. The limits of detection were in the range of 0.01 to 3 μg kg-1 with the two methods. The standards were prepared using the matrix matched standards due to the considerable matrix effects of the herbal medicines. Compared to the liquid method, the solid method required a smaller amount of sample, which is critical for PGR analysis of rare valuable herbal medicines. The two methods were applied for the determination of the twenty PGRs in different Chinese herbal medicine successfully.