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A simple and sensitive solid phase extraction of Zn2+ and Cu2+ in water samples employing Dithizone modified octadecyl (C-18) SPE sorbents was investigated. The effect of Phenanthroline and EDTA chelation of metals on extraction efficiencies of sorbents was compared for unmodified and dithizone modified C-18 sorbents.  Each C-18 SPE sorbent was pre-treated, and 100 ml of each sample of Zn2+ and Cu2+ (100µg/L) at different pHs (3.0, 5.0, 7.5 and 10) was percolated through the dithizone modified C-18 SPE sorbent at a steady flow rate of 5ml/min. The procedure of metal chelation was by mixing 100 ml of sample each with 2ml of EDTA and phenanthroline ligands (1000 mg/L) at varied pH and percolating through the C-18 pre-packed cartridge. The adsorbed metal ions were eluted with 5.0 mL of hydrochloric acid (1.0 mol/L) and concentrations were determined by flame atomic absorption spectrometry FAAS.  Recoveries from the sorbents were evaluated and expressed in percentage.  Recoveries were generally low (0.0-28.5%) for Cu2+ at the investigated pHs. Dithizone modified C-18 SPE gave better recoveries for 66.7 % of Zn samples but lower recoveries for Cu in 41.7 % of samples, when compared to the unmodified sorbent. SPE technique based on EDTA-Zn chelation resulted in optimum recovery (90.0%) for Zn at pH 3, while phenanthroline-Zn chelation produced optimum recovery (31.1%) at pH 10. The dithizone modified C-18 SPE sorbent produced better recoveries for Zn2+ from water samples when compared to unmodified one and could be a potential technique of sample preparation for determination of metals in water samples, hence warrants further investigation.   
Keywords: Solid Phase Extraction, ligands, modified, sorbent, recoveries