Preservation and Field Speciation of Inorganic Arsenic Species in Groundwater

This research describes the development of a dual preservationand field-speciation technique for As(III) and As(V) speciation of a sample preserved with ethylenediaminetetraacetic acid (EDTA) and acetic acid (HAc). The new method was compared with existing preservationand field-speciation methods and was shown to be accurate and precise in spite of possible interference from ferrous iron in the sample. The new preservation-speciation method was further evaluated on 55 drinking water wells (18 samples in triplicate) in Minnesota, North Dakota and California with the result that As(III) measured by field-speciation agreed with subsequent (within 1–3 d) laboratory speciation on the preserved sample with a slope of 0.98 and a correlation coefficient of r2 = 0.999. Preserved samples stored in the dark at room temperature (22–24oC) could maintain their species distribution for 30 to 85 d.