Click chemistry-mediated stable isotope labeling combined with HPLC-MS/MS analysis for highly sensitive determination of steroid hormones

Steroid hormone residues in food are a significant sources of endocrine disrupting chemicals (EDCs) that can adversely affect public health. However, the current analytical methods for determining steroid hormones using liquid chromatography-tandem mass spectrometry (LC-MS/MS) can be challenging due to the poor ionization efficiency of steroid hormones and the matrix effect of complex food samples. Herein, based on Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and stable isotope labeling (SIL) technique, a novel pair of chemoselective probes ABI / d 5 -ABI was precisely designed and synthesized. This pair of probes comprises a H/D isotope tag, a linker, a reactive site azido group (N 3 ) and a MS tag (imidazolium salt). The probe ABI was employed to label ethynyl-containing steroid hormones in real samples and d 5 -ABI was applied to label standards, respectively, followed by mixing the two labeled samples for high performance (HP)LC-MS/MS analysis. It was found that the ionization efficiencies of target analytes were increased by 17–4532 folds after ABI labeling. More importantly, the heavy labeled samples serving as internal standards (ISs) can effectively compensate matrix effect during HPLC-MS/MS analysis. Finally, the proposed SIL-HPLC-MS/MS method was successfully used to highly sensitive determine four synthetic steroid hormones in food samples (milk, pork and egg). Furthermore, the good detection limits (0.015–0.020 ng/mL), satisfactory recoveries (75.7–122.9 %), and precisions (RSDs less than 9.2 %) were obtained. Hence, the established method not only provides new insights in designing SIL probes for determination of ethynyl-containing analytes within complex matrix, but also extends the application of CuAAC reaction in the field of food chemistry.