Determinations of N-Nitrosodimethylamine (NDMA) at part-per-trillion (ng/L) concentrations in contaminated groundwaters and drinking waters featuring carbon-based membrane extraction disks

A new solid phase extraction procedure extracts N- Nitrosodimethylamine (NDMA) at part-per-trillion (ng/L) concentrations from aqueous samples using a C{sub 18} (reversed-phase) membrane extraction disk layered over a carbon-based extraction disk. The reversed-phase disk removes nonpolar water-insoluble neutrals and is set aside; the carbon-based disk is extracted with a small volume of dichloromethane. NDMA is quantitated in the organic extract using a gas chromatograph equipped with both a short-path thermal desorber and a chemiluminescent nitrogen detector (CLND). The Method Detection Limit for the procedure is 2 ng of NDMA/L; the analyte recovery is approximately 57%. A related procedure substitutes a standard automatic sampler for the short-path thermal desorber, and is suitable for determining NDMA in heavily-contaminated aqueous samples. The Method Detection Limit for the `high-level` procedure, which employs an automatic sampler, is 180 ng of NDMA/L, with an analyte recovery of approximately 64%