Determination of lead in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction.

Cloud point extraction (CPE) has been used for the pre-concentration of lead, after the formation of a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and later analysis by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation phase were optimized. Separation of the two phases was accomplished by centrifugation for 15min at 4000rpm. Under the optimum conditions i.e., pH 8.0, cloud point temperature 40 degrees C, [5-Br-PADAP]=2.5x10(-5)moll(-1), [Triton X-114]=0.05%, added methanol volume=0.15ml, pre-concentration of only 10ml sample permitted an enhancement factor of 50-fold. The lower limit of detection (LOD) obtained under the optimal conditions was 0.08mugl(-1). The precision for 10 replicate determinations at 5mugl(-1) Pb was 2.8% relative standard deviation (R.S.D.). The calibration graph using the pre-concentration system for lead was linear with a correlation coefficient of 0.9984 at levels near the detection limits up to at least 30mugl(-1). The method was successfully applied to the determination of lead in water samples.