| Summary: | 碩士 === 中山醫學大學 === 職業安全衛生學系碩士班 === 100 === N-nitrosamines are a class of probable human carcinogens. They often present in food, drinking water and environment. Human exposed to N-nitrosamines through ingestion and inhalation. In addition to exogenous exposure, N-nitrosamines can also be formed endogenously inside the body from its precursors, nitrate or nitrite and secondary or tertiary amines.
In this study, we developed an isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) with on-line solid-phase extraction (on-line SPE) for a quantitative analysis of nine N-nitrosamines in human urine, namely N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitrosomorpholine (NMor), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-buthylamine (NDBA) and N-nitrosodiphenylamine (NDPhA). Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) ion sources were evaluated and compared for nine N-nitrosamines determination. A 12 ml of crude urine was added with isotopic internal standards, then purified by activated carbon and concentrated to 0.1 ml under a high purity nitrogen stream. A 10 μl aliquot of prepared sample was then directly injected into the on-line SPE LC-MS/MS. The results showed that in the ESI mode, limit of detection (LOD) for NDMA, NMEA, NPyr, NDEA, NPip, NMor, NDPA, NDBA, NDPhA were 0.88, 0.15, 0.11, 0.09, 0.08, 0.03, 0.01, 0.003, 0.0004 fmol, respectively, while in the APCI mode, the LOD for NDMA, NMEA, NPyr, NDEA, NPip, NMor, NDPA, NDBA were 0.04, 0.03, 0.04, 0.04, 0.09, 0.002, 0.02, 0.008 fmol, respectively. Because NDPhA is a thermally labile nitrosamine, it was unable to be quantitatively detected in the APCI mode.
This method was further applied to measure urinary nine N-nitrosamines levels in 44 healthy subjects. The results showed that among nine N-nitrosamines only NDMA (0.7±0.52 ng/mg creatinine), NMEA (0.04±0.04 ng/mg creatinine), NDEA (0.17±0.09 ng/mg creatinine), NPyr (0.12±0.05 ng/mg creatinine), NDBA (0.024±0.007 ng/mg creatinine), NDPhA (0.09±0.13 ng/mg creatinine) were detectable, while the others were under LODs of our method. Overall, the present method would be useful to assess the human exposure to N-nitrosamines.
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