Extraction-flow injection spectrofluorimetric measurement of dissolved oxygen in environmental waters using 2-thionaphthol

A simple and highly sensitive flow injection analysis for the spectrofluorimetric determination of dissolved oxygen (DO) in environmental waters was developed. The decrease in fluorescence, which is based on the reaction of 2-thionaphthol with iodine liberated in Winklerʹs method, was utilized as the DO detection system. The calibration graph was linear over the range 2?10-6-1.2?10-5mol/l iodine. The relative standard deviation (n=8) was below 1% for the 6?10-6mol/l iodine determination and the detection limit (S/N=3) was 4.9? 10-7mol/l. The sample frequency was 18h-1.