[Determination of nifedipine by differential spectrophotometry]

This paper reports a new method for determining nifedipine based on the unstable character of nifedipine to light. The absorbance was measured at 350 nm before and after light irradiation. In this method, the contents of nifedipine in tablets were determined by differential absorbance (delta A) and the assay of nifedipine was not affected by other components. Calibration graph was linear in the range of 10-60 micrograms/ml for delta A. The precision of the method was: 1.3% within-day and 1.9% between-days. The average recovery for nifedipine was 99.69%. The method is not only better in specificity and repeatability but also simple and rapid, it would be a new way of assay for nifedipine.