Flow injection spectrophotometric determination of acetylsalicylic acid in tablets after on-line microwave-assisted alkaline hydrolysis

Abstract

The proposed method is based on the on-line microwave-assisted alkaline hydrolysis of acetylsalicylic acid (ASA) to salicylic acid (SA) that reacts with Fe^III to form a complex that absorbs at 525 nm. Samples merged with NaOH were passed continuously through a domestic microwave oven in order to accelerate the hydrolysis of ASA. Under the best analytical conditions, the linearity of the calibration equation for ASA ranged from 25 to 250 µg ml^{– 1}. The precision for ten successive measurements of 200 µg ml^{– 1} ASA presented a relative standard deviation of 0.40%. The detection limit was 4.0 µg ml^{– 1} and recoveries of 99.1–101.0% were obtained for ASA. No interference was observed from the common excipients of tablets and other active substances such as ascorbic acid and caffeine. The proposed FI method is adequate for a large number of samples because it is not time consuming and permits the determination of ASA in 90 samples per hour.