First-derivative spectroscopic determination of acetaminophen and sodium salicylate in tablets.

A first-derivative spectroscopic method for the simultaneous determination of acetaminophen and sodium salicylate in tablets was developed. Solutions of this drug combination in acidic ethanol were analyzed using their respective spectral responses at 258.5 and 317.0 nm. The method, which can be used for tablet composite assay and content uniformity analysis, is linear for acetaminophen concentrations ranging from 0.0 to 21.6 micrograms/mL, and for sodium salicylate concentrations ranging from 0.0 to 36.0 micrograms/mL. Relative standard deviations for the assay of both drugs in commercial tablets were less than 2%, and recoveries of acetaminophen and sodium salicylate from spiked samples were 99.7 and 100.1%, respectively. The results obtained by first-derivative spectroscopy were in agreement with the results of a liquid chromatographic procedure for acetaminophen and a fluorometric method for sodium salicylate. The technique used for the selection of wavelengths for analysis is also described.