DETERMINATION OF ATRAZINE IN WATER BY MAGNETIC PARTICLE IMMUNOASSAY -COLLABORATIVE STUDY

A collaborative study was performed to determine mean recovery and pre cision for analysis of atrazine in drinking and surface waters by immu noassay. The study design was based on the blind duplicate test plan f or collaborative studies. Three blank waters (municipal drinking water , well water, and surface water) were spiked at 3 atrazine levels. Two water samples with naturally incurred atrazine loads were also spiked with atrazine at 3 levels. In the enzyme-linked immunoassay method, t he water sample is mixed with a pesticide-enzyme conjugate and added t o paramagnetic particles with triazine-specific antibodies attached. A fter separation of antibody-bound atrazine and atrazine-enzyme conjuga te from free components, the bound enzyme conjugate catalyzes a reacti on producing a colored end product. The color developed is inversely p roportional to the original concentration of atrazine in the water sam ple. Fourteen laboratories participated in the collaborative study. Da ta were analyzed for repeatability and reproducibility, and average re coveries at the spike levels were calculated. Over the concentration r ange tested, the mean recovery of atrazine spiked into blank and pesti cide-contaminated waters was 104%. Overall RSD(R) averaged about 40% f or atrazine concentrations near the method detection limit (0.05 mu g/ L) and about 15% at concentrations above 5 times the detection limit ( 0.25 mu g/L). Corresponding single-analyst RSD(r) values were 24 and 1 0%. Recovery and precision for the 3 blank water matrixes and the wate rs that had been naturally contaminated with atrazine showed no signif icant differences. The magnetic particle immunoassay for determination of atrazine in water has been adopted first action by AOAC INTERNATIO NAL.