Optimization of the Extraction in solid phase of Organophosphorus Pesticide Residues in Drinking Water, Using Graphitized Carbon Black Cartridges

The aim of this work was to optimize an analytical method to determine residues of 21 organophosphorus pesticides of different polarities in drinking water using graphitized carbon black extraction cartridges liquid-solid and gas chromatography. The extraction was performed passing 100 mL of sample at 5 mL/min through 250 mg black graphitized carbon previously conditioned. The elution was carried out with 2 x 0,5 mL of acetone (80:20) and 2 x 2,5 mL of ethyl acetate/acetone (80:20) in a normal position. The cartridge was then inverted and 2 x 2,5 mL of ethyl acetate/acetone (80:20) was added. The extracts were dried with Na2SO4 anhydrous, concentrated with nitrogen to 1 mL, triphenylphosphate was added as internal standard. Afterward, 1 mL of this was injected into Perkin Elmer chromatograph using nitrogen-phosphorus detector. At a concentration levels between 5mg/L to 100 mg/L the recovery percentages oscillated amid 2% and 104%, with variation coefficients between 1,66 and 8,25 %, recovering 17 of 21 pesticides. These results indicate that the liquid-solid extraction using black graphitized carbon cartridges is efficient and reproducible for the detection of organophosphorus pesticides in drinking water.