FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF ACETYLSALICYLIC-ACID IN TABLETS AFTER ONLINE MICROWAVE-ASSISTED ALKALINE-HYDROLYSIS

The proposed method is based on the on-line microwave-assisted alkalin e 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 ana lytical conditions, the linearity of the calibration equation for ASA ranged from 25 to 250 mu g ml(-1). The precision for ten successive me asurements of 200 mu g ml(-1) ASA presented a relative standard deviat ion of 0.40 %, The detection limit was 4.0 mu g ml(-1) and recoveries of 99.1-101.0% were obtained for ASA. No interference was observed fro m 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 t he determination of ASA in 90 samples per hour.