Collaborative study and ion exchange method for the determination of methyldopa, chlorothiazide, and hydrochlorothiazide in drug mixtures
Chu, R.
Journal - Association of Official Analytical Chemists 54(3): 603-608
1971
ISSN/ISBN: 0004-5756 PMID: 5162921 Document Number: 31332
A method for the assay of methyldopa with either chlorothiazide or hydrochlorothiazide was studied collaboratively by 8 laboratories. The method involves the use of AG50-4X, 100-200 mesh H+ cation exchange resin to resolve the compounds. The thiazides pass freely through the resin column, while methyldopa is retained and subsequently eluted with 1N methanolic HCl. The components are quantitatively measured by spectrophotometry at 280 (methyldopa), 277 (chlorothiazide), and 270 nm (hydrochlorothiazide). For the methyldopa-chlorothiazide combination, the overall average recovery for methyldopa was 98.5% with a standard deviation of 2.50; and for the methyldopa-hydrochlorothiazide combination, 96.4% with a standard deviation of 2.30. The average recoveries for chlorothiazide and hydrochlorothiazide were 99.6 (standard deviation of 1.14) and 98.8% (standard deviation of 2.92), respectively. The method has been adopted as official first action for the determination of methyldopa and chlorothiazide in combination.