Study of the ESI and APCI interfaces for the UPLC–MS/MS analysis of pesticides in traditional Chinese herbal medicine

Abstract

In this work, 53 selected pesticides of different chemical groups were extracted from Chinese herbal medicines and determined by ultra-high-performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) using both electrospray ionization (ESI) and atmospheric-pressure chemical ionization (APCI). Extracts were obtained using the acetonitrile-based quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation technique. Cleanup was performed by dispersive solid-phase extraction using primary secondary amine, graphitized carbon black, and octadecylsilane. Two atmospheric-pressure interfaces, ESI and APCI, were checked and compared. The validation study, including detection limits, linearity, and matrix effects, was conducted on fritillaria, radix ginseng, folium isatidis, semen persicae, and flos lonicerae in multiple reaction monitoring mode. These matrices represent a variety of plants used in traditional Chinese medicine. Fritillaria and radix ginseng were chosen as representatives for roots, folium isatidis was chosen as a representative for leaves, semen persicae was chosen as a representative for seeds, and flos lonicerae was chosen as a representative for flowers. The limits of detection for pesticides were lower in the UHPLC-ESI-MS/MS method than in the UHPLC-APCI-MS/MS method. Matrix effects on the two ionizations were evaluated for the five matrices. Soft signal enhancement in UHPLC-APCI-MS/MS and signal suppression in UHPLC-ESI-MS/MS were observed.