LAUSR

An improved preconcentration method named as cloud point extraction (CPE) with ultraviolet– visible spectrophotometry (UV-vis) has been developed for zinc preconcentration and determination. Non-ionic surfactant Triton X-100 was used as extractant based on the complexation reaction of Zn (II) ions with 1-(2-pyridylazo)-2-naphthol (PAN). Sodium dodecyl sulfate (SDS) and NaCl electrolyte solution worked as cloud point revulsant and synergic reagent, which successfully decreased the cloud point temperature (CPT) of Triton X-100 to 0 °C. The enriched analyte in the surfactant-rich phase was determined by spectrophotometry at 549 nm. The influence factors relevant to CPE were evaluated and optimized, including concentrations of Triton X-100 and SDS, concentration of chelating agent, pH as well as salt effect. Under the optimal conditions, the proposed CPE-UV-vis method showed linear calibration within the range 10-1000 ng/mL of Zn (II) and the limit of detection of the method was 3.3 ng/mL with a preconcentration factor of 38. The relative standard deviation (RSD) was found to be 2.8% (CZn (II) = 100 ng/mL, n = 11). The proposed method was applicable to the determination of trace levels of zinc in real water, soil and blood samples with satisfactory results.