Micellar-enhanced photochemically induced fluorescence detection of chlorophenoxyacid herbicides. Flow injection analysis of mecoprop and 2,4-dichlorophenoxyacetic acid

In this paper, a combination of a flow injection analysis (FIA) system with micellar-enhanced photochemically induced fluorescence (MEPIF) detection i s presented as a powerful alternative for the rapid and sensitive analysis of chlorophenoxyacid herbicides. These compounds do not show native fluores cence but they can be photolysed into strongly fluorescence photoproducts a fter direct irradiation with ultraviolet light. The use of a cationic surfa ctant such as cetyltrimethylammonium chloride (CTAC) provides a considerabl e enhancement of photochemically induced fluorescence intensity and the nat ure of the technique allows a possible and easy adaptation to a FIA system. In this sense, parameters related to the nature of the analytical signal ( pH, irradiation times, surfactant concentration) and to the FIA manifold (i njection volume, flow rate and reactor length) have been optimised. Linear calibration graphs, with three replicates for each concentration value were established in the range of 0.2-5.0 mug ml(-1) for 2,4-Dichlorophenoxyacet ic acid (2,4-D) and 0.1-5.0 mug ml(-1) for Mecoprop (MCPP). The IUPAC detec tion limits were 73.2 and 33.5 ng ml(-1) for 2,4-D and MCPP, respectively. Satisfactory recoveries were obtained in the analysis of these herbicides i n spiked waters. (C) 2001 Elsevier Science BN. All rights reserved.