PHOTOCHEMICAL-FLUOROMETRIC METHOD FOR THE DETERMINATION OF TOTAL CHLOROPHENOXYACID HERBICIDES

A room temperature photochemically-induced fluorescence (RTPF) method is proposed for the quantitative analysis of seven widely-used chlorop henoxyacid herbicides. The influence of organic solvent, pH (in aqueou s solutions), methanol percentage, and UV irradiation time on the exci tation and emission wavelengths and fluorescence intensity was investi gated. It was found that the largest fluorescence signals were obtaine d in a mixture of methanol and pH 5 buffer (50/50, v/v), while organic solvents and water produced generally lower signals. The tri- and bic hlorinated phenoxyacid herbicides were photolysed significantly more s lowly than the monochlorinated derivatives, and the derivatives of 2-p ropionic acid were photodegraded more quickly than the corresponding d erivatives of acetic and butyric acid. Selected UV irradiation times w ere found to be 15 min for all herbicides under study. Linear calibrat ion graphs were established. over about one to two orders of magnitude in the interval 0.1-10 mu g ml(-1). The RTPF limits of detection were between 36 ng ml(-1) and 179 ng ml(-1), according to the compound. An alytical application of RTPF to river water samples containing chlorop henoxyacid herbicides is discussed.