HPLC determination of rubber septum contaminants in the iodinated intravenous contrast agent (sodium iothalamate).

A simple and rapid method is described for the determination of 2-mercaptobenzothiazole and mercaptobenzothiazole disulfide leached from rubber closures into the iodinated contrast medium (sodium iothalamate). The contaminants were extracted with methylene chloride and analyzed by high-performance liquid chromatography using ultraviolet detection at wavelengths of 272 and 328 nm. The structures of the impurities were confirmed unequivocally by mass spectrometry. The minimum detectable level was 1 microgram/100 mL (0.01 ppm). The quantitation of contaminants leached from rubber stoppers provides a means for evaluating possible health risks of the extractables.