Titrimetric determination of dipyrone and paracetamol with potassium hexacyanoferrate(III) in an acidic medium

Abstract

A method is described for the determination of dipyrone and paracetamol in pharmaceutical preparations in which aliquots containing 1–15 mg of the sample are allowed to react with a known excess of potassium hexacyanoferrate(III) in 10 ml of 8 M sulphuric acid and 5 ml of 3% zinc sulphate solution at 35 °C in a thermostatically controlled water-bath for 15 min (paracetamol) or 25 min (dipyrone). The excess of potassium hexacyanoferrate(III) is then determined iodimetrically. The analysis of a mixture containing dipyrone and paracetamol in pharmaceutical preparations is carried out after their separation, which is based on the difference in their solubilities. On treatment with distilled water, dipyrone goes into solution while paracetamol remains insoluble and is subsequently dissolved in hydrochloric acid by heating on a boiling water-bath for 30 min. Results are within a ± 1.0% error.