Interlaboratory quality study of the analysis of water for pesticides.

An interlaboratory quality control study was conducted to provide information to 5 participating Canadian laboratories on their capability in analyzing natural waters for 10 pesticides. The study was designed to identify the quality of each laboratory's working standards for 15 organochlorine pesticides, and the accuracy and precision of each laboratory's analytical procedures. Fifteen samples were provided, of which 3 were standards prepared for direct injection into an electron capture gas chromatograph. Instructions were provided to use these 3 standards for quantitating the pesticide content (8-150 ng/L) in 5 pairs of 1 L water samples. These paired samples contained 10 organochlorine pesticides approaching natural levels. Results of the study indicated that participants were fairly precise and achieved the designed ratio 1.5 for concentrations in the paired samples.