Spectrophotometric determination of vitamin B2 (riboflavin) in pharmaceutical formulations using flow injection analysis.

A flow injection spectrophotometric procedure exploiting merging zones is proposed for determining vitamin B-2 (riboflavin) in pharmaceutical preparations. The determination is based on the red-colored complex formation between vitamin B-2 and silver(I) which was measured at 520 nm. Vitamin B-2 was determined in four pharmaceutical preparations in the 1.0 to 50.0 mg L-1 concentration range, with a detection limit of 0.5 mg L-1. The recovery from three samples ranged from 98.0 to 104.0 %. The analytical frequency was 42 h(-1) and r.s.d. were lower than 1% for solutions containing 10.0, 30.0 and 50.0 mg L-1 vitamin B-2 (n= 10). The results obtained in commercial formulations using the FIA procedure were in good agreement with those obtained by using a conventional fluorimetric procedure (r=0.9998) and also with the label values (r= 0.9997).