SPECTROPHOTOMETRIC FLOW INJECTION DETERMINATION OF L-ASCORBIC-ACID WITH A PACKED REACTOR CONTAINING FERRIC HYDROXIDE

A flow injection system with spectrophotometric detection is proposed for determining L-ascorbic acid in pharmaceutical formulations. In thi s system a column containing Fe(OH)(3) immobilized in polyester resin (packed reactor) is inserted before the detector. Fe(III)-1,10-phenant hroline complex is reduced by L-ascorbic acid to produce Fe(II)-1,10-p henanthroline complex which is monitored at 510 nn. Under the optimum analytical conditions, the linearity of the calibration equation for L -ascorbic acid ranged from 5.0 x 10(-6) to 6.0 x 10(-5) M of added amo unt. The detection limit was 5.0 x 10(-7) M and recoveries between 98. 5-102.0% were obtained. No interference was observed from the common e xcipients of pharmaceutical formulations and other active substances s uch as acetylsalicylic acid, caffeine and thiamine. (C) 1998 Elsevier Science B.V. All rights reserved.