Abstract: A sensitive method based on cloud point extraction (CPE) coupled with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was proposed for the determination of trace lead and cadmium in litchi and longan samples. Factors affecting the cloud point extraction of lead and cadmium, such as sodium diethyldithiocarbamate (DDTC) concentration, pH, TritonX-100 concentration, extraction time and interference ions were investigated. Results indicated that the optimal extraction parameters were pH 5.0, extraction temperature of 100 ℃, extraction time of 15 min, Triton X-100 concentration of 0.3%, DDTC concentration of 0.02 g/100 mL and sample flow rate of 0.3 mL/min. Under the optimal conditions, Pb and Cd were enriched by 30 folds and 26 folds, respectively. The limits of detection of Pb and Cd were 2 ng/mL and 0.1 ng/mL, and the relative standard deviations (RSDs) were 5.2% and 3.6%, respectively. The proposed method was successfully applied to the determination of lead and cadmium in litchi and longan samples.

Key words: cloud point extraction, thermospray flame furnace atomic absorption spectrometry, lead, cadmium, sodium diethyldithiocarbamate