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

摘要

A flow-injection alame atomic absorption spectrometry is proposed for indirect determiantion of ascorbic acid based on its reduicng action to Fe(III).The Fe(II),produced by the reduction of Fe(III),is on-line adsorbed on a mini-column filled iwth cation-exchange resin to concentrate,then is eluted reversely by 3 moll~(-1) nitric acid to nebulizer and is measured by flame atomic absorption spectrometry,while the excessive Fe(III) reacts with NH_4F to form anion [FeF_6]~(3-) and passes through the mini-column to be waste.When reaction and concentrating time is 60s ,the absorbance of Fe(II) is proportional to the concentration of ascorbic acid in the range from 0.1 to 50 mgl~(-1).The analytic frequency is 30 samples per hour.This method has been applied to the determiantion of ascorbic acid in Vitamin C tablets,Vitamin C injection,vegetables and fruit juice.The results obtained in the analysis agree well with those provided by iodimetry.