The use of nitrous acid (HNO2) for determination of paracetamol (acetoaminophen) in liquid and solid formulations employing flow injection system is described. The determination of this drug was carried out by reacting paracetamol with nitrous acid generated in-line and the product yielded was measured at 430 nm in alkaline medium. The analytical curve ranged from 9.7x10-5 to 6.2x10-3 mol L-1 of paracetamol, with a detection limit of 2.5x10-5 mol L-1. The relative standard deviations (RSDs) were smaller than 2% for solutions containing 1.2x10-4 and 2.8x10-4 mol L-1 of paracetamol (n=10) and 60 determinations per hour were obtained. The results of determination of paracetamol in pharmaceutical formulations obtained by the proposed FI procedure were in good agreement with those obtained using theUSP procedure at a confidence level of 95% and within an acceptable range of error.
Flow injection spectrophotometry; nitrous acid; paracetamol
