According to the Safety and Technical Specification for Cosmetics （2015）， the addition of chemical drugs to cosmetics is strictly prohibited. Anti-alopecia cosmetics are often found to contain illegal additions of prohibited drugs such as minoxidil， finasteride and other substances. Ultra-high performance liquid chromatography-tandem triple quadrupole-linear ion trap mass spectrometry （UHPLC-Q-TRAP/MS） has become a powerful technology for the simultaneous detection of illegal ingredients in cosmetics due to its advantages of rapid analysis， high sensitivity， high throughput and high selectivity. An ultra-high performance liquid chromatography-multiple reaction monitoring-information dependent acquisition-enhanced production scanning （UHPLC-MRM-IDA-EPI） method was developed to determine 13 JAK inhibitors in anti-alopecia cosmetics， including baricitinib， tofacitinib， ritlecitinib， peficitinib， abrocitinib， upadacitinib， ivarmacitinib， fedratinib， filgotinib， ruxolitinib， momelotinib， pacritinib and bozitinib. The influence of extraction solvents was investigated. Approximately 0.2 g of the sample was weighed and placed in a 50 mL graduated centrifuge tube with a cap. Then， 2 mL of 0.1% （v/v） aqueous formic acid and 10 mL of acetonitrile were added， followed by vortexing for 1 min. Subsequently， the mixture was sonicated in an ultrasonic bath for 15 min. Added 0.5 g of sodium chloride， and the mixture was centrifuged at 8 000 r/min for 8 min at 5 °C. The supernatant was transferred to another 50 mL graduated centrifuge tube with a cap. The residue was added with 10 mL of acetonitrile and the extraction procedure was repeated. After high-speed centrifugation， the supernatant was combined. The combined supernatant was added with 0.2 g of sodium chloride， and the mixture was frozen at ‒20 °C for 1 h. It was centrifuged at 8 000 r/min for 5 min at 5 °C. The acetonitrile layer was collected and filtered through a 0.22 μm organic filter membrane. The initial filtrate was discarded， and the subsequent filtrate was collected as the sample solution. A Ccolumn was used for chromatographic separation， enabling the successful separation of the analytes within 10 min. The mobile phase consisted of 0.1% （v/v） aqueous formic acid and acetonitrile， with gradient elution applied to optimize separation efficiency. The flow rate was set at 0.3 mL/min， and the column temperature was maintained at 40 ℃ to ensure consistent performance. A fixed injection volume of 2 μL was used to guarantee reproducibility and accuracy in the analysis. This configuration enabled the rapid and reliable separation of the target compounds. For the analysis of the 13 kinds of JAK inhibitors， an ESI source operating in positive ion mode was used with MRM-IDA-EPI detection. Quantification was performed by the external standard method using matrix-matched standard solutions. Good separation of the 13 JAK inhibitors was achieved under the optimized chromatographic conditions. Calibration curves were constructed by plotting the peak area of quantitative ions against the compound mass concentration. These curves exhibited excellent linearity within the investigated concentration range， withall exceeding 0.996. The limits of detection （LODs） and limits of quantification （LOQs） of the 13 JAK inhibitors were 1.5-1.7 ng/g and 9.2-10.9 ng/g. To validate accuracy and precision， two cosmetic matrices （water-soluble and cream） were tested at three levels： LOQ， 2×LOQ and 10×LOQ. Recoveries of the 13 JAK inhibitors ranged from 94.7% to 102.2% for the water-soluble matrix and from 92.4% to 99.2% for the cream matrix， with relative standard deviations （RSDs） ≤8.8%. This method is characterized by high efficiency， rapidity， accuracy， sensitivity and simplicity， making it a powerful tool for rapid risk screening and simultaneous quantitative analysis of JAK inhibitors in anti-alopecia cosmetics. 18r
