Sequential Injection Spectrophotometric Determination of Diclofenac in Urine and Pharmaceutical Formulations

This paper reports a sequential injection spectrophotometric method for determining the concentration of diclofenac (DCF) in urine samples and pharmaceutical formulations. The method is based on the reaction of DCF with potassium permanganate in an alkaline medium. The influence on the analytical signal of the reactor length, the permanganate volume, the sample volume and the flow rate was investigated using a Taguchi parameter design. Under optimal conditions, the linear range of the calibration curve varied from 10.0 to 100.0 mg l, with a detection limit of 5.0 mg l. A sampling rate of 15 determinations h was achieved; the relative standard deviation of analytical repeatability was less than 3.0% in all cases. The method was validated by comparing the results obtained against those provided by RP-HPLC; no significant differences were seen (p<0.05)