Simultaneous determination of 7 pyrrolizidine alkaloids and their nitrogen oxides in herbal tea by SPE-UPLC-MS/MS

A analysis method for simultaneous determination of 7 pyrrolizidine alkaloids and their nitrogen oxides (monocrotaline, monocrotaline Noxide, lycopsamine, lycopsamine-N-oxide, heliosinine, heliosinine-N-oxide, senecionine) in herbal tea was established by solid phase extraction-ultra high performance liquid chromatography tandem mass spectrometry (SPE-UPLC-MS/MS). The samples were extracted by 0.1 mol/L hydrochloric acid solution and purified by MCX solid phase extraction column, separated by Poroshell 120 EC-C₁₈ chromatographic column (150 mm×3.0 mm, 2.7 μm), and detected by electrospray positive ionization multiple reaction monitoring (MRM) mode. The results showed that the 7 pyrrolizidine alkaloids and their nitrogen oxides showed good linear relationships in the linear range of 1.0-50 μg/L, and the correlation coefficients (R²) were both greater than 0.998. The limits of detection (LOD) and limits of quantitation (LOQ) were 0.3 μg/kg and 1.0 μg/kg, respectively. Average spiked recovery rates were 81.8%-98.8%, and the relative standard deviations (RSD) of precision experiment results were 1.98%-7.08%. The results of 20 herbal tea samples tested were found that 2 samples were detected with senecionine, which were 18.2 μg/kg and 33.5 μg/kg, respectively. The method was rapid, accurate, accurate and suitable for simultaneous determination of pyrrolizidine alkaloids and their nitrogen oxides in herbal tea.