Extraction and preconcentration of nickel, cadmium, cobalt, and lead cations in aqueous samples using dispersive solid phase extraction performed in a narrow-bore tube

Over the past decades, industrialization and mining activities have been led to emergence and dispersal of various pollutants in ecosystems. Among these contaminants, most heavy metals as a hazardous class of environmental pollutants can be harmful to human health even at low concentrations [1]. For example, lead may cause brain damage, kidney injury, seizures, and anemia. Also, it is harmful to plants and animals [2]. Human exposure has risen dramatically as a result of global industrial revolution and plethora of their use in several industrial, agricultural, domestic, and technological applications. Heavy metals cannot be biodegraded, so they persist in the environment and cause pollution of air, soil, and water ecosystems [3]. Therefore, the management of efficient, inexpensive, safe, and environmentally friendly methods for identifying, limiting, and determination of metal pollutions is earnestly required.In this investigation, a new version of dispersive solid phase extraction performed in a narrow–bore tube using large volume of sample solution followed by HPLC–DAD has been proposed for the simultaneous determination of some heavy metals including Ni (II), Cd (II), Co (II), and Pb (II). In the proposed method, iso–propanol as a dispersive solvent is mixed with a few amount of C18 sorbent and used for dispersing the sorbent into an aqueous solution containing the formed oxinate complexes of the studied cations. By this action, the sorbent passes through the solution in a short time instead of passing the solution from the cartridge which is done in the conventional solid phase extraction in a long time. Some important parameters including type and amount of sorbent, type and volume of dispersive solvent, sorbent conditioning, extraction time, pH, kind of buffer, chelating agent concentration, salt addition, and elution solvent kind and volume which may affect the extraction efficiency were studied. Under the optimum extraction conditions, the method showed wide linear ranges. Enrichment factors and extraction recoveries were obtained in the ranges of 831–1073 and 50–64%, respectively. Limit of detections were in the range of 0.05–0.40 μg L-1. The relative standard deviations for intra and inter–day precisions were lower than 9% for all analytes at 10 or 50 µg L-1 concentrations (each analyte).