To evaluate the uncertainty for the determination of 10,11-dihydro-10-hydroxycarbazepine (MHD) in human plasma by ultra performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

An isotope-labeled internal standard was employed. Chromatographic separation was achieved within 3 min on a BEH C₁₈ column (2.1 mm×50.0 mm, 1.7 μm) using a gradient elution at a flow rate of 0.4 mL·min^-1, with a mobile phase consisting of methanol containing 0.1% formic acid and water containing 5% methanol plus 0.1% formic acid. Plasma sample concentrations were determined by UHPLC-MS/MS with electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The method was validated for selectivity, calibration curve, lower limit of quantification, precision, recovery, matrix effect, and stability. The influencing factors in the quantification of MHD were analyzed and evaluated to calculate the individual uncertainties, combined uncertainty, and finally the expanded uncertainty.

MHD demonstrated good linearity within the range of 0.03 to 6.00 mg·L^-1. The accuracy (bias from the theoretical concentration) for within-run and between-run analyses was within ±15%, and the precision (coefficient of variation) was within 13.32%. Plasma samples showed good stability under the following conditions: 9 hours at 25 ℃, 5 hours at 4 ℃, three freeze-thaw cycles, and storage at -80 ℃ for 18 days. Based on the calculated uncertainty values for each contributing factor, repeatability, matrix effect, and recovery represented the major sources of uncertainty for the low-concentration quality control (QC) sample, with values of 1.96×10^-2, 5.49×10^-2, and 7.25×10^-2, respectively. For the high-concentration QC sample, matrix effect and recovery contributed substantially to the overall uncertainty, with values of 4.92×10^-2 and 2.01×10^-2, respectively. The expanded uncertainties (P=95%, k=2) for MHD at low (0.09 mg·L^-1) and high (4.50 mg·L^-1) concentrations in human plasma were 1.62×10² mg·L^-1 and 0.48 mg·L^-1, respectively.

The measurement uncertainty of MHD concentration in human plasma determined by UHPLC-MS/MS is primarily contributed by repeatability, matrix effect and recovery at low concentration levels, while dominated by matrix effect and recovery at high concentrations