IA fast and reliable high-pressure liquid chromatography (HPLC)-inductively coupled plasma-mass spectrometry (ICP-MS) routine method was developed for the determination of inorganic arsenic [As(Ill) and As(V)], organic monomethylarsonate [MMA(V)], dimethylarsinate [DMA(V)], and arsenobetaine (As-B) in human urine. The complete method validation is described, including internal and external quality assurance. Limits of quantification for the As species are 0.1 pg/L, which is sufficient to determine background concentrations of the arsenic species in human urine. Additionally, total As in all urine samples was determined by conventional ICP-MS. Mean concentrations for 82 non-exposed inhabitants from northern Germany are 12.7, 5.9, 4.0, 0.23, 0.52, and 0.17 pg/L for total As, As-B, DMA(V), As(Ill), MMA(V), and As(V), respectively. Approximately 15% of the total As was not identified by the anion exchange HPLC-ICP-MS method, and could be other As metabolites in urine. Two case studies underline the need for As speciation, especially when total urinary arsenic concentrations are elevated. In the first case, we investigated the effect of seafood consumption on the concentration of different arsenic species in urine for different persons. A maximum enhancement of lotal As from 1 up to 2200 pg/L (2000 pg/t for As-B) was observed after a normal fish meal. The second case describes the exposure of a 7-year-old child to As(Ill) by inhalation of calcium arsenite powder. Five hours after exposure, the concentrations in the child's urine for As-B, DMA(V), As(l I I), MMA(V), and As(V) were < 0.1, 189, 304, 229, and 27 pg/t, respectively, and these concentrations were reduced to normal background values after 4 days.
