Determination of chemical forms of arsenic in environmental water for endemic arsenism disease area of Azuoqi by NAA

The areas of endemic arsenic disease in the Azuoqi belong to the drinking water type arsenism diseace area. A simple and sensitive method to identify the chemical forms of As was presented. Inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were separated by the use of coprecipitation and cation exchange chromatography combined with neutron activation analysis. Separation of inorganic and organic arsenic (MMA and DMA) was based on coprecipitation with Fe(OH) 3, inorganic arsenic was coprecipited quantitativelly, but MMA and DMA was not coprecipited at all. Experiments showed that MMA and DMA in solution were adsorbed on cation exchange resin in pH2. MMA was eluted by 60mL of 0.5mol/L acetic acid-ammonium acetate buffer (pH4.7) and then 60mL of 3mol/L NH 3·H 2O was used to strip the DMA. The recovery of MMA and DMA was 96% and 103%, respectivery.