Validation of a Spectrofluorimetric Method for the Determination of Thiram and Thiophanate Methyl Fungicides in Environmental Samples

The intensive use of thiram and thiophanate methyl fungicides in agriculture leaves residues on crops and contaminates groundwater and surface water bodies through leaching. For the purpose of monitoring pollution arising out their use a spectrofluorimetric method has been validated for screening these fungicides in environmental samples viz. water, soil and foodstuffs. The measurement of fluorescence intensity of cerium(III) species at 365 nm resulting from ceric ammonium nitrate oxidation of dimethyl dithiocarbamate and o-phenylene bis-thiourea (products of the reaction of thiram and thiophanate methyl respectively with potassium tert.-butoxide) formed the basis of the method. As little as 0.18 and 0.22 µg mL-1 of thiram and thiophanate methyl can be determined. A simple and rapid solid-phase extraction and purification procedure prior to the spectrofluorimetric determination shows high recoveries of these fungicides from spiked water and grain samples in the range 86.00-98.00% and 88.50-97.50% with a maximum RSD of 2.60 % indicates good accuracy and precision of the method. Their risk of contamination of water bodies as groundwater ubiquity score (GUS) has also been evaluated based on their adsorption study on four soils and values in the range -0.48 to 0.98 classify them as non-leacher fungicides.