OPTOSENSING OF HYDROCHLORIC-ACID BASED ON THE FLUORESCENCE QUENCHING OF A FLAVONE COPOLYMER

An optical fiber sensor for the continuous determination of hydrochlor ic acid is presented. It is based on the fluorescence quenching of a f lavone containing copolymer membrane by hydrochloric acid. The quenchi ng efficiency is greatly enhanced in the presence of Fe(III). This enh ancement is attributed to the primary inner filter effect, as well as the formation of a complex between the 4'-N,N-dimethylaminoflavone gro up in the copolymer and the Fe(III) species extracted from hydrochlori c acid solution. The optical response is linear and reversible for 0.1 0-6.00 mol L-1 HCl with a response time of the order of a second. The standard deviations for repeated alternative measurements of 0.20 and 2.00 mol L-1 hydrochloric acid are 0.32% and 0.46% (n = 10), respectiv ely, indicating a good reproducibility. Because of the covalently bond ing of the dye to polymer, the sensor exhibits also a good stability. Selectivity has also been evaluated for some potential interferents. T he sensor in conjunction with a flow-injection system can be used for on-line determination of hydrochloric acid.