Comparative solid phase extraction, solid phase microextraction, and immunoassay analyses of metolachlor in surface runoff and tile drainage

New analytical technologies are being developed as an aid to identify pollutants in the environment. An interlaboratory collaborative study was initiated to compare solid phase extraction−gas chromatography (SPE−GC), solid phase microextraction−gas chromatography (SPME−GC), and two enzyme-linked immunosorbent assay (ELISA) techniques for analysis of metolachlor in water samples from a field experiment. Concentration in the water samples ranged from <0.1 to 50 μg/L. Metolachlor concentration in water was highly correlated among methods (R2 range 0.80−0.97). Slope of regression lines and intercept values between SPE−GC, immunoassay (IA) i, and IA ii techniques did not differ from unity or zero compared to SPME−GC analysis. The two immunoassay methods agreed well with each other (R2 ranged from 0.94 to 0.97), and differences in concentration were mostly attributed to matrix effects. SPME and ELISA have great potential as tools to detect metolachlor in natural waters. Keywords: Solid phase microextraction; SP...