QuEChERS purification prior to stable isotope dilution-ultra-high performance liquid chromatography tandem mass spectrometry to determine organophosphate esters of trace amounts in dairy products

[摘要] A fast and simple method, based on QuEChERS purification and stable isotope dilution-ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS), was developed for the simultaneous determination of seven organophosphate esters (OPEs) in dairy products. Milk powder was first dispersed in warm water. Then 0.2% formic acid–acetonitrile was used for protein precipitation and the extraction of target OPEs from liquid milk and the re-dissolved milk powder. QuEChERS purification was adopted to purify the sample solution by using 50 mg primary secondary amine (PSA) as the sorbent. The results showed that the disturbance of complex matrices was significantly reduced and recoveries for all target analytes were acceptable after QuEChERS purification. The separation of seven OPEs was performed on a Phenomenex Kinetex PFP column and MS/MS detection was performed with an electrospray ionization (ESI) source in positive ion mode. Tri-n-butyl phosphate-d27 (TBP-d27) was used as a stable isotope internal standard. The method was validated in terms of linearity, sensitivity, precision and accuracy. Linear relations were favorable for seven OPEs over the selected concentration range of 1–200 μg L−1, with correlation coefficients (r) greater than 0.99. The limits of detection and quantification (LODs and LOQs) were in the ranges of 0.10–0.36 μg kg−1 and 0.50–1.50 μg kg−1, respectively. Suppression or enhancement of the signal was compensated for by the use of the isotopically labeled internal standard. Recoveries were satisfactory with values in the ranges of 90.1–105.5% for liquid milk and 83.5–110.5% for milk powder. Relative standard deviations (RSDs) of 2.6–7.9% for intra-day precision and 3.8–9.1% for inter-day precision were observed for all dairy products. The validated method was successfully applied to determine the concentrations of OPEs in dairy products.

[学科分类] 分析化学