CAPILLARY ELECTROPHORESIS DETERMINATION OF DIATRIZOIC ACID AND ITS IMPURITIES IN DIATRIZOATE RADIOPAQUE SOLUTIONS

A capillary electrophoresis method has been developed for the separati on and determination of diatrizoic acid (DTZA) and its four mono- and diiodo degradation products (2-iodo,4-iodo, 2,4-diiodo, and 2,6-diiodo -3,5-diacetamidobenzoic acid) in radiopaque solution for injection (RS I). DTZA and its degradants were assayed in suitable dilutions without pretreatment. Optimum conditions included the use of low-pressure sam ple injection (6 s), sample and standard solutions with a molarity les s than that of the separation buffer, and adjustment of the buffer mol arity to obtain a current of 50 mu A at a constant 15 kV separation vo ltage. After each six runs or less, the inlet and outlet buffer were r eplaced with more buffer from the same batch. When the method was appl ied to a sample of SI levels of 5-10 mg/ml were found for each of the mono and diiodo impurities. The optimum method showed a precision (pea k area measurement) in the range 1.7-7.2% RSD, depending on the concen tration. A linear correlation coefficient of 0.997 was obtained over a DTZA concentration range of 5-60 mg/mL.