Modification of the NH₂ column method for chromium speciation in surface water and soil water

A new application of the NH2 column method has been tested for speciation of Cr(VI) in soil water and surface water. Soil water and surface water samples were collected from two sites near the world’s largest stainless steel production plant, Outokumpu Tornio Works, about 10 km south of the City of Tornio, Finland. Dissolved chromium species [Cr(VI) and Cr(III)] were quantified immediately from the water samples with the NH2 (aminopropyl-modified silica) column method and a graphite furnace atomic absorption spectrophotometer (GFAAS) and then three months later after the collection. The sum of Cr species concentration determined by the method was equal to total dissolved Cr concentration measured by inductively coupled plasma mass spectrometry (ICP-MS). The method was precise and selective for environmental water samples at low concentrations, and it fractionated Cr species with 100 % specificity without noteworthy interference from other metals. Some difficulties appeared with Cr standard solutions made with deionised water. In addition, the soluble form of Cr(VI) was preserved in a stable form for three months both in the refrigerator and freezer, and almost all the dissolved Cr was in the Cr(VI) form