Comparison of assay methods by second-derivative spectroscopy, colorimetry and fluorescence spectroscopy of salicylic acid in aspirin preparations with a high-performance liquid chromatographic method.

Second-derivative spectroscopy, colorimetry and fluorescence spectroscopy have been compared with a high-performance liquid chromatographic (HPLC) method for the assay of salicylic acid in preparations of aspirin. Results are presented for the linearity, sensitivity and reproducibility of these methods. The second-derivative spectroscopic and the HPLC methods were acceptable in terms of linearity, sensitivity and inter-day reproducibility and were convenient for the routine analysis of salicylic acid in aspirin preparations.