Simultaneous determination of 15 pyrrolizidine alkaloids and their N-oxides in weeds, soil, fresh tea leaves, and tea: Exploring the pollution source of pyrrolizidine alkaloids in tea.

Pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs) are novel contaminants in tea. However, the source of PA/PANO contamination in tea remains unclear. In this study, 15 PAs/PANOs were extracted from plant samples (tea, fresh tea leaves, and weeds) with 0.1 M sulfuric acid and from soil with 0.1 M sulfuric acid methanol after adjusting soil acidity with 0.1 M trisodium citrate. Satisfactory recoveries of PAs/PANOs from four different matrices at 0.02, 0.1, and 0.5 mg kg-1 was 72%-114% with relative standard deviations (RSD) of 0.03%-16%. Seven out of 15 PAs/PANOs were detected in tea purchased from the local market ranging from undetected to 96.2 μg kg-1. Thirteen, three, and four PAs/PANOs were detected in weeds, fresh tea leaves, and soil, respectively. Based on the types of PAs/PANOs detected in the three matrices, it was preliminarily speculated that PAs/PANOs in tea originated from weeds in the tea garden.