DETECTION AND DETERMINATION OF DILUTE, LOW-MOLECULAR-WEIGHT ORGANIC-COMPOUNDS IN WATER BY 500-MHZ PROTON NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The feasibility of using high-field proton NMR spectroscopy to analyze aqueous solutions of organic solutes at micromolar concentrations has been evaluated. N-Nitrosodimethylamine (NDMA) and benzene served as model compounds. The WATR (water attenuation by transverse relaxation) method of solvent suppression was optimized to permit detection of the protons of analytes in the submicromolar concentration regime. All data were collected in blocks to permit quantitative estimation of detection limits and experimental error. Externally referenced peaks heights, rather than peak integrals, were used to measure solute concentration. The detection limit for NDMA, using a 500-MHz instrument for 2 h, was 510ng/mL and, for benzene, using a 4-h acquisition, was 35 ng/mL. The technique was used to monitor the effect of UV irradiation on a 10-mu-g/mL sample of NDMA. The NDMA was eliminated; the predominant photoproduct was dimethylamine (DMA).