Flow-injection, on-line concentrating and flame atomic absorption spectrometry for indirect determination of ascorbic acid based on the reduction of iron(III)

A flow-injection flame atomic absorption spectrometry is proposed for indir ect determination of ascorbic acid based on its reducing action to Fe(III). The Fe(II), produced by the reduction of Fe(III), is on-line adsorbed on a mini-column filled with cation-exchange resin to concentrate, then is elut ed reversely by 3 mol l(-1) nitric acid to nebulizer and is measured by fla me atomic absorption spectrometry, while the excessive Fe(II) reacts with N H4F to form anion [FeF6](3-) and passes through the mini-column to be waste . When reaction and concentrating time is 60 s, the absorbance of Fe(II) is proportional to the concentration of ascorbic acid in the range from 0.1 t o 50 mg l(-1). The analytic frequency is 30 samples per hour. This method h as been applied to the determination of ascorbic acid in Vitamin C tablets, Vitamin C injection, vegetables and fruit juice. The results obtained in t he analysis agreed well with those provided by iodimetry. (C) 2001 Elsevier Science B.V. All rights reserved.