Application of on-line HPLC-1H NMR to environmental samples: analysis of groundwater near ammunition plants
Coupling of HPLC to NMR was applied for the first time to the analysis of environmental samples, i.e., water samples from an ammunition hazardous waste site. Using the continuous flow mode at very low rates (<=0.017 mL/min) and large volume injection (400 microL), the confirmation of many nitroaromatic compounds could be achieved down to the microgram-per-liter level after solid phase extraction of a groundwater sample from a former ammunition production site. At a flow rate of 0.006 mL/min, it is possible to detect less than 29 nmol (5 microgram) of 1,3-dinitrobenzene injected on a 75 mm x 4 mm reversed phase C-18 column (particle size, 5 microgram). The results obtained by HPLC-NMR are compared to those obtained by HPLC-PDA (photodiode aray) of the same sample, demonstrating that many more compounds can be identified by the former compared to the latter method as a result of coelution of major and minor components in the HPLC chromatogram.