[Ratio spectrophotometry and its application to assay of compound pharmacy preparations].

The present paper is to study ratio spectrophotometry for its application to the assay of compound pharmacy preparations. According to the feature of ratio spectra, the wavelength pair was selected at the peak point or valley point of ratio spectra to establish ratio spectrophotometry for the determination of Co-Chlorzoxazone tablet and injection of caffeine and sodium benzoate. The average recoveries and relative standard deviations for Chlorzoxazone and paracetamol were 100.0% and 1.28%, and 100.0% and 0.84%, respectively; the average recoveries and relative standard deviations for caffeine and sodium benzoate were 99.98% and 0.70%, and 99.91% and 0.78%, respectively. It is concluded that as long as the ratio spectra exhibit at least one peak and one valley, the results are satisfactory.