Simultaneous Quantitative Screening for Pain Medications in Serum by High-Performance Liquid Chromatography/Time-of-Flight Mass Spectrometry with Solid-Phase Dispersive Extraction

In this study, solid-phase dispersive extraction (SPDE) was used for serum pretreatment and in the simultaneous analysis of analgesics and adjuvant analgesics (30 types in total) that are usually used as first-and second-choice treatments for pain patients, by liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS). Examination of the optimum conditions for SPDE using Oasis MCX as the solid-phase gel revealed that the recovery rates for serum samples deproteinized in advance were 49–87%, whereas the recovery rates were as high as 78–112% when deproteinization was not performed. The matrix effect was within ±10% regardless of the presence or absence of deproteinization, and its influence could be suppressed even if deproteinization was not performed. The results indicate that serum deproteinization was unnecessary when SPDE was used for pretreatment. In LC/TOF-MS measurement, gradient elution was carried out using core-shell type column Kinetex C18 (150 mm × 2.1 mm, 1.7 µm) as the LC column and 50 mM ammonium acetate buffer (pH 7.8)/acetonitrile/methanol mixture as the mobile phase. The 30 drugs were well separated, and the limit of quantification was 0.25–10 ng/mL, the correlation coefficients of the calibration curves were higher than 0.998, and the average recoveries ranged from 77.7 to 112.1%. The method would be useful to screen for analgesics and adjuvant analgesics (30 types in total) in serum in the fields of forensic science and emergency medicine.