determination of ni2+ and cr3+ in aqueous samples by graphite furnace atomic absorption spectrometry after preconcentration by organic gas steam liquid extraction

Heavy metals are well-known environmental pollutants due to their toxicity, persistence in the environment, and bioaccumulative nature [1]. the concentration of toxic heavy metals in water and food samples is fairly low and the interference due to matrix cannot be always eliminated. on the other hand, to cope with these problems, for real samples with complicated matrix, preconcentration procedure is necessary before determination of metal ions [2]. in this study, organic gas steam liquid extraction method was proposed as a simple and sensitive method for the preconcentration of ultra-trace amounts of ni2+ and cr3+ in water as a prior step to their determination by graphite furnace atomic absorption spectrometry. for this purpose, ammonium pyrrolidine dithiocarbamate (apdc) as a complexing agent and methyl isobutyl ketone (mibk) as extracting solvent was used, also, in order to obtain a high extraction recovery, the effect of different parameters such as the volume of organic solvent, the molar ratio of the extracting agent relative to metal, the ph of the aqueous phase, the extraction time and the temperature of the heating chamber were investigated. under the optimized conditions, the limit of detection (lod), limit of quantification (loq) of this method, linear concentration range and percentage of the relative standard deviation were found. to evaluate the selectivity of the proposed method, the interference effects of some common ions including na+, k+, ca2+, mg2+, fe3+, co2+, no3- and cl-, on the recovery of ni and cr were investigated. the average recovery for the extraction of nickel and chromium was over 85%. the limit of detection was 0.38 and 0.25 μgl−1 for ni2+ and cr3+ respectively. the proposed method was successfully applied to the determination of ni and cr in water samples.