A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest, such as fungi, insects, rodents, and weeds [1]. Pesticides are used intensively in modern agriculture. Because they are hazardous to human health and the environment, it is important to control pesticide residues after their application to food. Considerable attention is focused on regulating the allowable limits for pesticide residues in food and drinking water. For example, the European Union directives set the maximum admissible concentration of 0.1 μg/L for each pesticide in drinking water and 0.5 μg/L for the sum of pesticides [2,3]. Thus, analytical methods with detection limits as low as 0.02 μg/L [4] are required for pesticide monitoring in drinking water. This leads to the need for new methods of analysis to quantify the large number of pesticides that can be found at such low levels in water [5].