Home-built LC-MiniMS system for quantification of tacrolimus in whole blood

Precise assessment of tacrolimus (TAC) concentrations is critical in clinical diagnostics, and liquid chromatography–mass spectrometry (LC-MS/MS) is the preferred approach due to its high specificity and sensitivity. However, classic LC-MS/MS systems are frequently enormous, costly, and need expert operation, which restricts its applicability in numerous industries. In this paper, a liquid chromatography–miniature mass spectrometry (LC-MiniMS) system was designed and developed. The miniature linear ion trap spectrometer had a footprint of 59 × 38 × 27 cm 3 , which substantially reduced the instrument size and cost while maintaining quantitative performance. The LC-MiniMS system’s circuit boards were integrated and the software automation was optimized, so it was more convenient to use and maintain. Results demonstrated excellent linearity over the range of 0.5–50 ng/mL with R 2 > 0.99. The limit of detection and limit of quantification were 0.1 and 0.3 ng/mL, respectively. The accuracy ranged from 99.67% to 106.10%, intraday precision was between 0.70% and 2.61%, and interday precision was between 0.90% and 2.90%, all within acceptable limits, and matrix effects were negligible. The method was successfully applied to quantify TAC in 32 clinical whole-blood samples, and the results strongly agreed with those from a conventional LC-MS/MS system (QTRAP 6500+). The LC-MiniMS system can efficiently quantify TAC in whole blood and provide a tiny, cost-effective, and uncomplicated option for therapeutic drug monitoring in clinical settings, especially in decentralized or resource-limited scenarios.