Flow-injection spectrophotometric method with on-line photodegradation for determination of ascorbic acid and total sugars in fruit juices

This article reports a flow-injection spectrophotometric determination (FIA) with a photodegradation step to determine ascorbic acid and total sugars. The flow-injection system includes a simple ultraviolet photoreactor for the on-line photodegradation. The method is based on the determination of ascorbic acid at 300 nm before the photodegradation step, followed by UV irradiation and measurement of total sugars at 268 nm. The proposed method was used to determine ascorbic acid and total sugars in commercial and natural fruit juice samples. The method was validated by using spiked samples with recoveries in the range 96.4–108.3% for ascorbic acid, and 91.0–113.2% for total sugars.