Suspension Dispersive Solid Phase Extraction for Preconcentration and Determination of Cobalt, Copper, and Nickel in Environmental Water by Flame Atomic Absorption Spectrometry

A novel preconcentration technique termed suspension dispersive solid phase extraction (SDSPE) was developed for selective separation and preconcentration of cobalt, nickel, and copper in environmental water. The method is based on the reaction of zinc sulfate and sodium hydroxide to form zinc hydroxide. The suspension results from the dispersion of the fine particles of the sorbent in the aqueous sample. The complexes of metal ions in the bulk aqueous sample with 1-(2-pyridylazo)-2-naphthol (PAN) were loaded on sorbents. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was eluted by methanol and determined by flame atomic absorption spectrometry. Key parameters such as the type and mass of sorbent, type and volume of eluent, concentration of the chelating agent, equilibration time, and sample volume were optimized and an enrichment factor of 20 was obtained with a sample volume of 40mL. The limits of detection for Co, Ni, and Cu were 2.4, 1.7, and 1.5 mu gL(-1), respectively. The relative standard deviations were 4.3%, 2.7%, and 1.6% at 10 mu gL(-1) for Co, Ni, and Cu, respectively. The method was successfully employed for the determination of these metals in environmental waters.