Preparation of a new sorbent, cetyltrimethylammonium bromide (CTAB)-modified obsidian, for the separation, preconcentration of Pb(II), Cd(II) ions in food and water samples

Cetyltrimethylammonium bromide (CTAB)-modified obsidian (CTAB-OB) was utilized as a new sorbent for the separation and preconcentration of Pb(II) and Cd(II) ions by solid phase extraction in some environmental samples prior to their flame atomic absorption spectrophotometric determination. The characterization of CTAB-OB was performed by BET surface area,FTIR and SEM techniques. The effects of significant analytical parameters,including pH of the aqueous solution,eluent type,concentration and volume,CTAB-OB amount,sample volume,adsorption and desorption contact time,were evaluated in detail on the recovery of the analyte ions. The adsorption capacity of CTAB-OB was found to be 48.8 and 43.4 mg g-1 for the Pb(II) and Cd(II) ions,respectively. The detection limits for the analyte ions were 0.89 μg L-1 for Pb(II) and 0.37 μg L-1 for Cd(II),while the relative standard deviations were lower than 3.5% for both of them. In order to ensure the accuracy of the method,certified reference material (CRM-SA-C Sandy Soil C) analyses and spike tests were performed. Then the proposed method was applied to sea and stream water,black tea,and Turkish and import coffee samples to determine their Pb(II) and Cd(II) contents.