Multi-residue determination of pesticides in star anise by a QuEChERS and gas chromatography tandem mass spectrometry-based method

The star anise is a challenging substrate for pesticide residue analysis because of complex matrix interference. Efforts were made in this work to establish a robust method for analysis of pesticide multi-residues in the star anise. The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for pretreatment of star anise was evaluated and optimised. By adopting the optimised matrix purification method, the content of non-volatile matrix co-extracts of star anise was reduced by 63% compared to the unpurified procedure. The matrix-matched calibration standards were used to reduce the influence of strong matrix effect. Combined with gas chromatography tandem mass spectrometry (GC­MS/MS) detection, residues of 227 pesticides in the star anise were validated. In the optimised method, 216 target substances (95% of total tested) obtained satisfactory recoveries (72–119%) and relative standard deviations (1–10%) at three spiking levels, and established a method limit of quantification (LOQ) of 0.05 mg kg⁻¹. Moreover, the optimised method was successfully employed to analyse target pesticides in star anise market samples. The residues of tebuconazole, difenoconazole, methoprene, chlorpyrifos, propoxur and piperonyl butoxide were detected.