Flow injection fluorimetric determination of ascorbic acid based on its photooxidation by thionine blue.

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 x 10(-7) to 5 x 10(-5) mol l-1 with a throughout 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.