Development of determination method of trace nickel in natural water by ID-oxygen added nitrogen-MIP-MS with direct measurement of liquid-liquid extracted organic phase

This work introduces the development of a novel determination method of trace nickel (ng l(-1) level) in natural water samples. Nickel in the water samples is liquid-liquid extracted into methyl isobutyl ketone (MIBK) as nickel-diethyldithiocarbamate (DDTC) complex, and isotope dilution-oxygen added nitrogen-microwave induced plasma mass spectrometry (ID-oxygen added nitrogen-MIP-MS) is conducted by direct measurement of the liquid-liquid extracted organic MIBK phase. The accuracy of the proposed method was confirmed by analysing certified reference materials (NRC NASS-5 seawater, NRC SLRS-3 riverine water and NRC SLRS-4 river water), and the analytical results obtained were in good agreement with the certified values. The detection limit for nickel is 1.3 ng l(-1) when the water sample is 50 times concentrated. The precision as RSD is < 4%. The proposed method was applied to clarify the concentration-depth vertical profiles of nickel in Lake Mashu, Japan, as the Baseline Station of the United Nations GEMS/Water (Global Environment Monitoring System/Water) Programme.