Double injection–single detector flow injection spectrophotometric method for simultaneous determination of ascorbic acid and paracetamol in pharmaceutical formulations

Abstract

A simple and low-cost flow injection spectrophotometric method was proposed for the simultaneous determination of ascorbic acid (AA) and paracetamol (PCM) in pharmaceutical formulations. The present method is based on the reduction of Fe(III) to Fe(II) with AA and PCM in a closed flow system which subsequently combines with the 1,10-phenanthroline to form an orange-coloured complex that is measured at 510 nm. The increase in the absorbance was proportional to the concentration of AA in the range of 0.1–12 µg/ml with a correlation coefficient of 0.9997 and detection limit of 0.31 µg/ml, and to the concentration of PCM in the range of 0.4–24 µg/ml with a correlation coefficient of 0.9999 and detection limit of 0.39 µg/ml. The precision for ten serial estimations of 2 and 7 µg/ml of AA exhibited a relative standard deviation of 3.33% and 2.47% and of 6 and 15 µg/ml of PCM with a relative standard deviation of 3.008% and 2.23%, respectively. The present FI method permits determination of 9 samples per hour with no interference from the common excipients. The developed method was applied to different tablets containing AA and PCM with the recovery of AA from four spiked samples ranged from 95.31 to 104.73%, and of PCM ranged from 95.03 to 104.93%.