A procedure for separation and pre-concentration of trace amounts of cadmium, copper, lead, nickel, and zinc in brine samples has been proposed. It is based on the adsorption of metal ions onto dithizone co-crystallized with microcrystalline naphthalene, in the pH range 8.5-9.1. Nitric acid is used to back-extract the cations from the solid phase, which are measured by ICP-OES. Various parameters, such as the effect of pH, stirring time, and amounts of solid phase, have been studied in detail, to optimize the conditions for the determination of trace amounts of Cd, Cu, Pb, Ni and Zn in synthetic brine samples. The limits of detection values expressed in μg L-1 are 44 (Zn), 11 (Ni), 30 (Cd), 47 (Pb) and 11 (Cu). The precision of the procedure was determined by running 10 replicate samples, each one containing 250 μg L-1 of each element and the relative standard deviations were 2.71 % (Cd), 2.15 % (Cu), 1.53 % (Pb), 2.47 % (Ni), and 2.78 % (Zn). The accuracy of the procedure was confirmed by applying the analyte additions method and the results indicated that quantitative recoveries (≥ 95 %) were obtained.
preconcentration; solid-liquid extraction; naphthalene; dithizone; highly saline matrices
