Yukihiko Umeno

Simultaneous determination of phenylbutazone and its metabolites in plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the simultaneous determination of phenylbutazone and its metabolites, oxyphenbutazone and gamma-hydroxy-phenylbutazone, in plasma and urine. Samples were acidified with hydrochloric acid and extracted with benzene--cyclohexane (1:1, v/v). The extract was redissolved in methanol and chromatographed on a muBondapak C18 column using a mobile phase of methanol--0.01 M sodium acetate buffer (pH 4.0) in a linear gradient (50 to 100% methanol at 5% min; flow-rate 2.0 ml/min) in a high-performance liquid chromatograph equipped with an ultraviolet absorbance detector (254 nm). The detection limit for phenylbutazone, oxyphenbutazone and for gamma-hydroxyphenylbutazone was 0.05 microgram/ml. A precise and sensitive assay for the determination of phenylbutazone and its metabolites was established.

Quantitative determination of 1,3-bis(tetrahydro-2- furanyl)-5-fluoro-2,4-pyrimidinedione and its metabolites in plasma by high-pressure liquid chromatography and gas chromatography-mass fragmentography.

1,3-Bis(tetrahydro-2-furanyl)-5-fluoro-2,4-pyrimidinedione has been developed clinically as an antitumor agent. A high-pressure liquid chromatographic method was developed with which it could be measured in plasma with a sensitivity of 0.050 microgram/ml. Two of its metabolites, 1-(tetrahydro-2-furanyl)-5-fluoro-2,4-pyrimidinedione and 3-(tetrahydro-2-furanyl)-5-fluoro-2,4-pyrimidinedione, could be determined at the same time with a sensitivity of 0.025 microgram/ml. A gas chromatographic-mass fragmentographic method was developed for the specific determination of the third metabolite, 5-fluoro-2,4-pyrimidinedione, as its silylated derivative with a sensitivity of 0.001 microgram/ml. The precision and sensitivity of the assay appear to be satisfactory for determination of the plasma level of the drug.

Gas chromatographic-mass fragmentographic determination of propiverine and its metabolites in plasma and urine

1-Methyl-4-piperidyl diphenylpropoxyacetate hydrochloride has been developed clinically for the therapy of urinary bladder dysfunction. A gas chromatographic-mass fragmentographic method was developed for the determination of this drug and its seven metabolites in plasma and urine. The sample was first treated with a Sep-Pak C18 cartridge, the methanol eluate was evaporated to dryness, and the resulting residue was redissolved in distilled water. This solution was then extracted with chloroform and adjusted to pH 9.0 with 0.1 M sodium borate solution. The acidified aqueous layers were extracted with ethyl acetate. The chloroform layer, which contained non-polar metabolites, was concentrated to dryness, then subjected to trifluoroacetylation, decomposition and methylation. The extract from the plasma sample was trimethylsilylated. The dried residue of the ethyl acetate layer, which contained polar metabolites, was subjected to methylation, trifluoroacetylation and decomposition. Aliquots of each reactant solution were injected into the gas chromatograph-mass spectrometer and analysed by the selected-ion monitoring method using an internal standard. Detection was limited to 1-2 ng/ml of plasma and urine for each metabolite. A precise and sensitive assay for the determination of 1-methyl-4-piperidyl diphenylpropoxyacetate hydrochloride and its metabolites in plasma and urine was thus established, and it should prove useful in basic and clinical pharmacological studies.

Analysis of pyrimidine bases in biological materials by gas chromatography-mass spectrometry.

Simultaneous detection by a combination of gas chromatography-mass fragmentography and gas chromatography-mass spectrometry for total ion monitoring was developed for determination of uracil, thymine and cytosine present in biological materials as pyrimidine bases, as their silylated derivatives. The detection limits for uracil, thymine and cytosine in the first method were 0.001 microgram/ml for plasma and 0.001-0.005 microgram/g wet weight for tissues. Those for uracil and thymine in plasma and tissues and for cytosine in plasma in the second method were 0.2 microgram/ml or g wet weight, and that for cytosine in tissues was 2.5 microgram/g wet weight. An accurate and sensitive assay for determination of pyrimidine bases was established.

Gas chromatographic-negative-ion chemical ionization mass spectrometric determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolites in human plasma and urine

A gas chromatographic-negative-ion chemical ionization mass spectrometric method was developed for the determination of a new calcium antagonist, (+/-)-methyl 2-oxopropyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedicarboxylate, and its metabolites in plasma and urine. The sample was extracted with n-hexane-diethyl ether. The dried organic layer was subjected to acetylation: the aqueous layer was acidified and extracted with ethyl acetate, and after the ethyl acetate extract was dried the resulting residue was subjected to methylation. Aliquots of each reactant solution were injected into the gas chromatograph-mass spectrometer, equipped with a chemical ionization source and negative-ion monitoring mode, and analysed by the selected-ion monitoring method using deuterium-labelled internal standards. Detection was limited to 0.02-0.05 ng/ml of plasma and urine for each metabolite. A precise and sensitive assay for the determination of a new dihydropyridine calcium antagonist and its metabolites in plasma and urine was thus established.

Gas chromatographic--mass fragmentographic determination of homopantothenic acid in plasma.

A gas chromatographic--mass fragmentographic method was developed for the determination of homopantothenic acid in plasma. Acidified plasma was deproteinized by extraction with chloroform and subsequently the aqueous layer was extracted with ethyl acetate. The organic layer containing homopantothenic acid was reduced to dryness, and the resulting residue was redissolved in N,O-bis(trimethylsilyl)trifluoroacetamide--pyridine solution to allow trimethylsilylation. Aliquots of this solution were injected into the gas chromatograph--mass spectrometer and analyzed by the selected ion monitoring method using L-ascorbic acid as an internal standard. The detection limit for homopantothenic acid was 5 ng/ml of plasma. A precise and sensitive assay for the determination of homopantothenic acid in plasma was established.