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 this system a column containing Fe(OH)(3) immobilized in polyester resin (packed reactor) is inserted before the detector. Fe(III)-1,10-phenanthroline complex is reduced by L-ascorbic acid to produce Fe(II)-1,10-phenanthroline 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 amount. 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 excipients of pharmaceutical formulations and other active substances such as acetylsalicylic acid, caffeine and thiamine. (C) 1998 Elsevier Science B.V. All rights reserved.