Determination of pesticide residues in drainage water

Abstract

Pesticides are used worldwide within agriculture to protect crops and ensure the quantity and quality of the harvest. However, intensive and inappropriate pesticides application can directly or indirectly affect different parts of the environment, especially water source. Besides the occurrence of pesticides in drinking water, control of pesticide presence in surface and groundwater is also very important. This primarily refers to the drainage water, river and groundwater, considering the importance of environmental protection and food safety production. The presence of pesticide residues in these matrices may cause yield reduction and decrease product quality, due to its uptake. Objectives of this study included drainage water investigations to identify residue levels of selected pesticides. The sampling was performed during June 2012. Water samples were taken from drainage canals, on twelve sampling points, in intensively cultivated regions of Serbia, Vojvodina Province. Pesticides were chosen based on the European Union Directive 2008/105/EC. This directive by Annex X defines the List of priority substances in the field of water policy. List includes 33 pollutant - 9 are pesticides. The extraction of pesticides from water was performed using 018 ENVI (TM) disc (47 mm). Prior to extraction disc was conditioned with 5 ml of methanol and 5 ml of deionized water. Afterward, water sample was filtered through the disc under vacuum. After drying under vacuum (25 degrees C for 1 h), pesticides were eluted from the disc with 5 ml of mixture of dichloromethane/n-hexane (40/60, v/v) and evaporated to dryness. The extract was dissolved in 1 ml of methanol, ultrasonically homogenized and analyzed. The pesticide residues concentrations analyzed by gas chromatography/electron capture detection with Ni-63. Identification is performed by the use of GC/MS. The mean recovery of this extraction method for all analyzed pesticides at 1 mu g/ml, 0.1 pg/ml and 0.01 pg/ml spiking levels was 93.6%, with associated standard deviations (RSD) of 2.7. The limit of quantification was 0.01 pg/ml. Method accuracy was quantified through measurement uncertainty estimate based on method validation data. The combined relative uncertainty for water samples was 0.481%, while the expanded uncertainty (Us) calculated as U-c=k*U-c, where k is the coverage factor with level of confidence of approximately 95% considering a coverage factor of 2 (EURACHEM/CITAC, 2000), was 0.962%. Obtained values of evaluated analytical parameters are completely in accordance with regulations for analysis of pesticides trace level. Described method was applied for determination of above mentioned pesticides in real water samples. Finally, acetochlor, alachlor and chlorpyrifos were detected in drainage water samples collected in the agricultural area of Serbia.