ANALYSIS OF CARBAMATE PESTICIDES BY PACKED-COLUMN SUPERCRITICAL-FLUID CHROMATOGRAPHY

The carbamate pesticides in EPA Method 531.1 are separated in 9 min by packed-column supercritical fluid chromatography under steady-state conditions. All (except the naphthol degradation product of carbaryl) are directly, selectively detected without derivatization using a nitrogen-phosphorus detector (NPD). All the compounds are simultaneously detected by UV absorption, offering additional qualitative information. Solid-phase extraction is used to preconcentrate the solutes and change the solvent from water to ethyl acetate. Preliminary detection limits as low as 110 parts per trillion are found. Similar results are obtained when the loop of the injection valve is replaced with a short precolumn. Water samples are pumped through the precolumn, which is then dried and re-wetted with 5 µL methanol. Chromatographic selectivity is a complex function of temperature, pressure, and composition with many peak reversals. The carbamates and two groups of breakdown products each exhibit different selectivities. © 1994 Oxford University Press.