Quantitative determination of fluvastatin in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry using [18O2]-fluvastatin as an internal standard.
ABSTRACT A sensitive and specific method for the quantitative determination of fluvastatin in human plasma is presented. The drug was isolated from plasma by extractive alkylation with pentafluorobenzyl bromide and further derivatized to the bis-trimethylsilyl derivative. [18O2]-Fluvastatin was prepared from unlabelled fluvastatin and used as an internal standard. Gas chromatography/mass spectrometry under negative ion chemical ionization conditions was used for quantitative measurement of the drug, using m/z 554.26 and 558.26 for target and internal standard, respectively. Calibration graphs were linear within a range of 2 and 512 ng mL(-1) plasma. Intra-day precision was 0.94% (2 ng mL(-1)), 2.53% (8.2 ng mL(-1)), 2.16% (81.9 ng mL(-1)) and 3.26% (409.6 ng mL(-1)); inter-day variability was found to be 1.64% (2 ng mL(-1)), 0.97% (8.2 ng mL(-1)), 1.97% (81.9 ng mL(-1)) and 2.01% (409.6 ng mL(-1)). Intra-day accuracy showed deviations of 0.6% (2 ng mL(-1)), 0.37% (8.2 ng mL(-1)), -1.52% (81.9 ng mL(-1)) and -1.67% (409.6 ng mL(-1)); inter-day accuracy was of -1.64% (2 ng mL(-1)), -1.13% (8.2 ng mL(-1)), -2.28% (81.9 ng mL(-1)) and -0.46% (409.6 ng mL(-1)). The stable isotope labelled standard was found to be stable under the analytical conditions.
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ABSTRACT: Plasma pseudocholinesterase and porcine liver esterase were used to catalyse the incorporation of the stable isotope oxygen-18 into the carboxyl moiety of lipoxygenase metabolites of arachidonic acid. This simple method produces eicosanoid products containing two oxygen-18 atoms; but the enzymes studied were found to display large substrate specificity in the efficiencies at which oxygen-18 could be incorporated into the lipoxygenase metabolites. Furthermore, [18O2]LTB4 was found not to back exchange during in vitro incubation with human neutrophils. The methods involved for stable isotope incorporation are simple, efficient and produce highly enriched species in a short time. By varying the type of esterase, the amount of esterase or the length of incubation highly enriched species of all eicosanoids tested could be prepared.Biomedical mass spectrometry 01/1986; 12(12):714-8.
- Medicinal Research Reviews 04/1991; 11(2):121-46. · 9.58 Impact Factor
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ABSTRACT: A specific method for the quantitative determination of valproic acid in human plasma is presented. Valproate was extracted from acidified plasma by hexane extraction and converted to its trimethylsilyl derivative without sample concentration. The derivatives were analyzed without any further purification. Using gas chromatography-electron ionization mass spectrometry, diagnostic useful fragment ions at m/z 201 and 205 were obtained for valproic acid and [(18)O(2)]valproic acid internal standard, respectively. [(18)O(2)]Valproic acid was synthesized from unlabeled valproate by acid-catalyzed exchange reaction in H(2)(18)O. The method was validated in the expected concentration range of a pharmacokinetic study. Thus, calibration graphs were linear within a range of 0.47-120 microgram/ml plasma. Intra-day precision was 2.29% (0.47 microgram/ml), 2.93% (4 microgram/ml), 3.22% (20 microgram/ml) and 4.40% (80 microgram/ml), inter-day variability was found to be 1.49% (0.47 microgram/ml), 3.79% (20 microgram/ml), 2.74% (40 microgram/ml) and 3.03% (80 microgram/ml). Inter-day accuracy showed deviations of 1.94% (0.47 microgram/ml), 0.53% (4 microgram/ml), -0.32% (20 microgram/ml) and 0.06% (80 microgram/ml). The method is rugged and robust and has been applied to the batch analysis of valproate during pharmacokinetic profiling of the drug.Journal of Chromatography B 02/2003; 784(1):69-75. · 2.49 Impact Factor