Determination of Trace Nickel in Water by UV-Visible Spectrophotometry after Cloud Point Extraction

Cloud point extraction with Triton X-100 and sodium dodecyl sulfate(SDS) as mixed surfactants,1-(2-pyridylazo)-2-naphthol(PAN) as chelating reagent and NaCl electrolyte for pre-concentrating trace levels of nickel,which as a prior step to its spectrophotometric determination has been studied in this paper.The parameters affecting the separation phase and detection process were investigated,and the optimal conditions at room temperature were followed: 5.5 mL of saturated NaCl,0.125 mL of 0.1% PAN,the ratio of SDS and Triton X-100 were between 0.38 and 1.39.Under the optimum experimental conditions,calibration curve was linear in the range of 0.1~1.0 mg·L-1 with R2=0.999 8,and the detection limits is 18.9 μg·L-1.The spiked recovery of nickel were 97%~99%.The relative standard deviation(RSD,n=4) was in the range of 2%～4%.