Semiautomated method for analysis of nitroglycerin in sublingual tablets: collaborative study

This method is a semiautomated version of the current USP XX method for content uniformity testing of nitroglycerin tablets. Nitroglycerin is hydrolyzed to nitrite in aqueous alkali. The nitrite thus formed diazotizes procaine, which then is coupled with Bratton-Marshall reagent; the absorbance of the resultant color is read at 550 nm. Six collaborators were supplied with 6 composites of sublingual tablets, representing 3 different dosage levels. Results agreed with those obtained by the author using the USP composite assay method. The coefficients of variation ranged from 0.20 to 0.70%. The method is sensitive enough for individual tablet assays (0.15 mg nitroglycerin). The method has been adopted as official first action.