Recyclable non-ligand dual cloud point extraction method for determination of lead in food samples.

A new pH-mediated non-ligand dual cloud point extraction (NL-DCPE) was first developed for extraction Pb(II) from food samples. The NL-DCPE method includes two cloud point extraction (CPE) steps and the recycling of the copolymer. The first procedure was based on the forming of lead hydroxide at pH 9.5 and subsequent lead hydroxide was entrapped in a thermoseparating triblock copolymer [(PEO)10(PPO)23(PEO)10] (L44) phase. At second stage, the copolymer-rich phase was treated with the acidic solution, and Pb(II) was back extracted into the aqueous phase. So the problem emerging from the high viscosity of the copolymer-rich phase can be well solved. Under the optimized conditions, the extraction efficiency of 97.20% and detection limit of 1.9 μg L(-1) were obtained. Moreover, the copolymer L44 was successfully recycled and reused for more than two times. This method was successfully used for analyzing Pb(II) in food samples with satisfactory recoveries in the range of 94.01-101.19%.