Determination of bupivacaine tissue concentration in human biopsy samples using high‐performance liquid chromatography with mass spectrometry

Abstract

In the present study, we developed a simple and rapid analytical method for the quantification of bupivacaine hydrochloride in human biopsy samples of adipose, muscle, neural, connective and cartilage tissue using liquid chromatography‐mass spectrometry. Anesthetics were extracted from the tissue samples using 0.1% formic acid in acetonitrile for protein denaturation and hexane for removal of lipophilic impurities. Analytes were separated adequately on Phenomenex Luna Omega polar C18 column using a gradient mobile phase 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The lower limits of quantification were ≤ 97 ng g−1 tissue for all studied tissues. Intra‐day recoveries were between 48.2% and 82.1% with relative standard deviations (RSDs) between 1.47% and 14.28%, whereas inter‐day recoveries were between 52.2% and 77.6% with RSDs between 2.98% and 14.79%. The calibration curve showed a linear fit with R2 higher than 0.99 in the concentration range from 0.16 to 100 μg g−1. Lidocaine hydrochloride was tested as internal standard because its recoveries and matrix effects were comparable to bupivacaine hydrochloride. Post‐analytical corrections of measured bupivacaine tissue concentrations can accordingly be made based on recovery of lidocaine as internal standard, with recoveries between 51.2% and 86.9% and RSDs between 1.99% and 16.88%. The developed method could be used to study time‐dependent spread of bupivacaine locally or to more distant locations across tissue barriers.