Determination of Trace Amount of Cobalt in Water Samples by Spectrophotometry with Cloud Point Extraction

Trace level cobalt in water was extracted and preconcentrated by cloud point extraction (CPE) and determined by spectrophotometry.The sodium dodecyl sulfate (SDS) was acided by HCl and NaCl as hydrophobic ligand and 1-(2-pyridylazo)-2-naphthol (PAN) as complexing reagent.The chemical variables affecting CPE were evaluated and optimized.The optimum conditions are as 1.90mol/L NaCl,1.20 mol/L HCl,3×10 -2 mmol/L PAN,1.25% SDS,60℃ in a thermostated bath for 50min,centrifugated at 2400r/min for 5 min. Under the optimized condition,the concentrations of cobalt showed a linear range of 16.7—83.3μg/L.The limit of detection of 2.870 μg/L for cobalt with the enhancenment factor of 50 and relative standard deviation of 0.96%? ?.30% (n=5).The method was applied to the determination of cobalt in water samples with satisfactory result.