Abstract
The aim of this study was to develop and to validate a UPLC-MS/MS method for the quantification of morphine, morphine-3-glucuronide, and morphine-6-glucuronide in mouse plasma and tissue homogenates to support preclinical pharmacokinetic studies. The sample preparation consisted of protein precipitation with cold (2-8 °C) methanol:acetonitrile (1:1, v/v), evaporation of the supernatant to dryness, and reconstitution of the dry-extracts in 4 mM ammonium formate pH 3.5. Separation was achieved on a Waters UPLC HSS T3 column (150 × 2.1 mm, 1.8 µm) maintained at 50 °C and using gradient elution with a total runtime of 6.7 min. Mobile phase A consisted of 4 mM ammonium formate pH 3.5 and mobile phase B of 0.1% formic acid in methanol:acetonitrile (1:1, v/v). Detection was carried out by tandem mass spectrometry with electrospray ionization in the positive ion mode. The method was validated within a linear range of 1-2,000 ng/mL, 10-20,000 ng/mL, and 0.5-200 ng/mL for morphine, morphine-3-glucuronide, and morphine-6-glucuronide, respectively. In human plasma, the intra- and inter-run precision of all analytes, including the lower limit of quantification levels, were ≤ 15.8%, and the accuracies were between 88.1 and 111.9%. It has been shown that calibration standards prepared in control human plasma can be used for the quantification of the analytes in mouse plasma and tissue homogenates. The applicability of the method was successfully demonstrated in a preclinical pharmacokinetic study in mice.