Comparison of analyses of wastewaters for N-nitrosamines using various detectors

Three GC detectors, the AFID, the TEA and the Hall (pyrolytic mode), were evaluated for the monitoring of wastewaters for NDMA, NDPA and NDPhA. All three detectors were adequate for NDMA and NDPA determinations. Due to its thermal lability, NDPhA has to be determined indirectly as its degradation product, DPhA, using the AFID. A column clean-up method for removing DPhA from samples prior to GC analysis is described. Since both the TEA and the Hall (pyrolytic mode) detectors utilize pyrolysis after gas chromatography, they are not satisfactory for NDPhA monitoring. Wastewater analysis using all three detectors gave comparable data; however, the lack of nitrosamine selectivity in the AFID requires both that the sample undergo an initial clean-up and a longer GC bake-off time. It is also noted that the Hall detector used in the pyrolytic mode may offer some advantages for routine nitrosamine monitoring; and is less restricted in its utility than the TEA.