A Method Using Liquid-Liquid Microextraction in a Dynamic System for Preconcentration and Determination of Lead in Food Samples

In this paper, a method using liquid-liquid microextraction in a dynamic system combined with spectrophotometry was developed for preconcentration and determination of lead in samples of shrimp and oyster. In the procedure, a system is proposed in which the organic drop is maintained at the bottom of a glass tube, with the passage of a stream of aqueous solution, avoiding the use of a microsyringe. The method is based on the transfer of metal species present in the aqueous phase in the form of complexes with the ligand 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol (5-Br-PADAP) to the organic phase trichloroethylene. Experimental conditions, such as sample flow rate, concentration of the complexing reagent, extraction solvent, time of extraction, and pH, were optimized. Under optimized conditions, the limit of detection and quantification obtained were 0.48 and 1.60 μg L−1, respectively. The accuracy was evaluated by the determination of lead in the certified reference material BCR-414, Plankton. The procedure was applied to the determination of lead in samples of shellfish, with recoveries ranging from 92 to 103 %. The method enabled a fast, accurate, and simple alternative for the determination of lead in seafood samples.