Using dimethyl indocarbocyanide (DIC) as ion-pair agent for chromium speciation and its application in GFAAS analysis of water

A novel procedure for the determination of Cr(VI) using electrothermal atomic absorption spectrometry with Zeeman background correction was developed. The method is based on the reaction of Cr(VI) with dimethyl indocarbocyanine (DIC) in acidic medium in the presence of chloride ion followed by liquid–liquid extraction of the ion associate formed and subsequent GFAAS detection. The optimum conditions (pH, concentrations of chloride ion and DIC) were determined for the extraction of Cr(VI) into toluene. Furthermore, the effect of temperature on the separation, the stability of the complex formed, possibilities of preconcentration and possible interference of Fe, Cd, Co, Ba, Al, Hg, Zn, Ni, Cu, V, Mn and Pb were studied as well. The detection limit (LOD) of the method for Cr(VI) was found to be 0.25 μg L−1 and RSD was mostly better than 5% using a 1 : 1 ratio for the organic and water phases.