Chlorpyrifos contamination in soil and water: method development and the application of environmental models / Norshidah Baharuddin

The work presented here focuses on the extract clean-up since this step is usually time-consuming, requires large quantities of organic solvents, and contributes significant amount of errors. Several clean-up techniques based on solid-phase extraction used in the analysis of chlorpyrifos residue in soil and water were evaluated. Recoveries of chlorpyrifos residue in soil via PS-1 filter paper, C8 and silica cartridges were in the range of 97.1%, 95.7% and 109.2% with standard deviation (SD) of 0.8%, 4.8% and 10.1%, respectively. The use of PS-1 filter paper was recommended based on the good reproducibility, faster analysis and low cost. For the clean-up of water sample, the performance of C8 and C18 cartridges with variation of pH and methanol volume were compared and the recoveries of chlorpyrifos were in the range of 52% to 102% with SD of 2.1% to 13.3%. The use of C8 with 1% methanol and pH adjusted to 2.0 was recommended. The chosen methods were used to analyse chlorpyrifos content in water and soil samples collected from Tanjung Karang paddy field for 2 paddy planting seasons. In the effort to predict the amount of this compound in the environment, the applicability of chemical fate models was investigated. Two environmental models, EQC level III and ChemCAN 4 were evaluated by comparing the actual amount of chlorpyrifos with the value predicted by the models. The values from the EQC level III model was found to be of the same order as the actual values, while those predicted by ChemCAN 4 model is 100 times smaller than the actual values.