Applicability of cloud point extraction for the separation trace amount of lead ion in environmental and biological samples prior to determination by flame atomic absorption spectrometry

A sensitive cloud point extraction procedure(CPE) for the preconcentration of trace lead prior to its determination by flame atomic absorption spectrometry (FAAS) has been developed. The CPE method is based on the complex of Pb(II) ion with 1-(2-pyridylazo)-2-naphthol (PAN), and then entrapped in the non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of PAN and Triton X-114, equilibration temperature and time, were investigated in detail. A preconcentration factor of 30 was obtained for the preconcentration of Pb(II) ion with 15.0 mL solution. Under the optimal conditions, the calibration curve was linear in the range of 7.5 ng mL−1-3.5 μg mL−1 of lead with R2 = 0.9998 (n = 10). Detection limit based on three times the standard deviation of the blank (3Sb) was 5.27 ng mL−1. Eight replicate determinations of 1.0 μg mL−1 lead gave a mean absorbance of 0.275 with a relative standard deviation of 1.6%. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method has been applied for determination of trace amounts of lead in biological and water samples with satisfactory results.