Determination of ascorbic acid by use of a flow-through solid phase UV spectrophotometric system

A continuous flow-through solid phase spectrophotometric system was develop ed for the determination of ascorbic acid based on the measurement of its i ntrinsic absorbance in the UV region when retained on a 1 mm Sephadex QAE A -25 anion exchanger gel layer which is placed into an appropriate quartz fl ow-through cell, the absorbance exhibited by this solid phase being monitor ed at 267 nm. A monochannel manifold was used, the sample (300, 600 or 1000 mu L) being injected into the carrier solution (acetate buffer). This solu tion also elutes the analyte after developing the analytical signal, and re generates es the resin layer which, therefore, remains ready for the next s ample. The linear dynamic range and other analytical parameters vary accord ing to the sample volume injected. Three calibration lines were established for 300, 600 and 1000 mu L sample volume, which ranged from 1.0 to 20.0, 0 .5 to 10.0 and 0.2 to 6.0 mu g mL(-1), respectively. The detection limits w ere 0.04 (300 mu L), 0.03 (600 mu L) and 0.02 mu g mL(-1) (1000 mu L), the sampling rates 28, 24 and 21 h(-1), and the RSDs (n = 10) 0.87%, 1.08% and 0.90%, respectively. The amount of ascorbic acid in various samples (pharma ceuticals, sweets and urine) were successfully determined with this method.