Tomás Pérez-Ruiz, Carmen Martínez-Lozano, Virginia Tomás and Ciriaco Sidrach
The photooxidation of ascorbic acid sensitized by Thionine Blue was studied. The Leucothionine Blue formed during the reaction is highly fluorescent. A flow injection method using merging zones is proposed for the determination of ascorbic acid over a concentration range from 8 × 10-7 to 5 × 10-5 mol l-1 with a throughput of 80 samples per h. The method was used for the simple and rapid determination of ascorbic acid in pharmaceuticals, fruit juices and soft drinks.