We report a fast, simple high-performance liquid-chromatographic assay for serum alpha-tocopherol, with use of a reversed-phase column and tocol as internal standard. Only 200 microliter of serum is required. Isocratic elution of the n-hexane extract is done within 6 min; total analysis time is less than 1 h. Within-day precision (CV) was 2.3% for 24 samples of a normal plasma pool (mean concn, 10.1 mg/liter). Day-to-day precision (CV) was 3.2%, measured for 20 days for a specimen with a concentration of 10.8 mg/liter. Analytical recovery of alpha-tocopherol from fortified serum was 89 to 100%. The lower detection limit of alpha-tocopherol is estimated to be 0.6 mg/liter. The specificity of the procedure was verified by spectrophotometry, gas-liquid chromatography, and combined gas chromatography/mass spectrometry of an eluate collected from the column.
Abstract-Identification of hydrazine monoamine oxidase inhibitor drugs such as isoniazid, iproniazid, nialamide, isocarboxazid and iproclozide is made by electron impact mass spectrometry using the direct insertion technique. The molecular ion itself, although of low relative abundance, is found in the mass spectra of all compounds studied. Relative intensities of the major fragments and data on metastable ions useful in the identification of these compounds are reported. With the aid of synthesized structurally related products, deuterium labelling of exchangeable hydrazidic and hydrazinic protons and by the use of hexadeuterated isopropylic analogues, detailed information about fragmentation patterns is obtained. Splitting processes are chiefly governed by the nature of the aromatic substituent at the hydrazidic end and the alkyl sidechain located at the second hydrazinic nitrogen. The major fragmentations occurring are loss of small neutral molecules, double rearrangement, cleavage of the N-N bond, amide bond rupture, P-cleavage to the hydrazinic nitrogen atom and McLafferty rearrangements
Fluorouracil in human plasma of a concentration as low as 2 ng ml-1 can be assayed with the use of gas-liquid chromatography and a multiple ion detector. Fluorouracil is isolated from plasma by anion exchange extraction. The extract is butylated and the derivative obtained extracted into a mixture of cyclohexane + dichloromethane (95:5). An aliquot is submitted to combined gas-liquid chromatography mass spectrometry. The use of chlorouracil or oxygen-18 labelled fluorouracil as internal standard is discussed. Linearity is proven from 100 microgram to 5 ng of fluorouracil per ml plasma. The coefficients of variation are 7.2 and 8.4% for within-run and between-run precision, respectively, at the 50 ng ml-1 level. The biological applicability of our procedure is demonstrated by analysing plasma samples obtained at different time intervals from three patients given 1 g of fluorouracil once intravenously and once orally.
A procedure is described for the separation of Vitamin D and related compounds by gas-liquid chromatography using flame ionization detection. The method involves a two-step conversion: isomerization to the corresponding (all trans) isotachysterol(s) followed by methyl ether derivatization of the alcohol group(s). The procedure provides a means for identification as well as a possible basis for quantitation of Vitamin D and analogs.
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