Hartvig P, Fagerlund C, Gyllenhaal O. Electron-capture gas chromatography of plasma sulphonylureas after extractive methylation.
JOURNAL OF CHROMATOGRAPHY 1980;
181:17-24. [PMID:
7364911 DOI:
10.1016/s0378-4347(00)81264-5]
[Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Conditions for the extractive alkylation of eight sulphonylurea hypoglycemic drugs have been evaluated. Extractive methylation of the compounds was achieved within 90 min using tetrabutylammonium as counter-ion (0.1 M at pH = 6.9) with 5% methyl iodide in dichloro-methane as organic phase. Mass spectral analysis showed derivatives methylated at the sulphonamide nitrogen. A higher pH or use of tetrapentylammonium as counter-ion caused hydrolysis of the sulphonylureas. The derivatives showed a high electron-capture response with minimum concentrations detectable in the range 1-4 x 10(-16) moles sec-1. Therapeutic plasma concentrations of glipzide and tolbutamide were determined by direct extractive methylation of the compounds from the plasma sample. The glipizide derivative was determined by electron-capture gas chromatography down to about 20 ng/ml in a 0.5-ml plasma sample. The relative standard deviation at the 0.2 microgram/ml level of glipizide was 6% (n = 6). The corresponding figure in the determination of tolbutamide at the 10 microgram/ml level was 3% (n = 10).
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