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UV degradation and pH adjustment for fluorescence detection of metsulfuron methyl as common herbicide used for plant treatment was tested. Experimental work was focused on different fluorescent behavior of ionized form and degradation components produced during UV decomposition at 245 and 366 nm. Fluorescence detection was tested with respect to dissolution of the metsulfuron methyl in different organic solvents too. Sequential injection technique was applied throughout the study because of its simplicity, low consumption of samples and quick analysis. Mainly in case of organic solvents their consumption and waste production was decreased using the mentioned flow method. UV decomposition was carried out following previous work of Caselli [1] and effect of various decomposition ways producing different degradation components was examined. UV degradation was observed in 15, 30 and 60 min intervals without or with pH adjustment to the value 2 using sulfuric acid in aqueous, acetone, mixture of water and acetone (in the ratio of 7:3) and chloroform solutions. The fluorescent signal in case of metsulfuron methyl in chloroform solutions with pH adjustment (without UV decomposition) was found to be 54-times higher compared to aqueous solutions of the same conditions. And in comparison of chloroform solution with pH adjustment and UV decomposition and aqueous solution with the same pre-treatment even 66-times higher fluorescence was observed. Calibration of metsulfuron methyl in chloroform solution with pH adjustment was linear over the range of 5?25 mg L?1 with correlation coefficient 0.999 and limits of detection and quantitation were 1.52 and 5.13 mg L?1, respectively, without any other sample pre-concentration that is supposed to be needed for real samples analysis.