Determination of trace chromium(VI) in water by graphite furnace atomic absorption spectrophotometry after preconcentration on a soluble membrane filter

Abstract

 A new method for the concentration and determination of <0.1 μg/L of Cr(VI) in water by GFAAS is described. It is based on the formation of a chromium(VI)-salicylfluorone (SAF)-tetradecylpyridinium(TDP) ternary complex, the collection of the complex on a soluble membrane filter and the detection of the solution obtained after dissolving the membrane and analyte in a proper solvent. The ternary complex [Cr(VI)-SAF-TDP=1:2:2] is collected on a 0.45 μm nitrocellulose filter. This is dissolved in a small volume of sulphuric acid and the chromium is determined by GFAAS under the optimized conditions. Good linearity is observed over the range 0.010–0.150 μg Cr(VI) in 5.0 mL. The detection limit (three times the standard deviation of the blank) is 0.04 μg/L with 50-fold preconcentration. No interference from ions normally present in water was observed. The method has been applied to the concentration and determination of Cr(VI) in water samples from several sources and the recoveries of added Cr(VI) were 91–101%.