Preparation of Modified MWCNT with Dithiooxamide for Preconcentration and Determination of Trace Amounts of Cobalt Ions in Food and Natural Water Samples

A fast, sensitive and simple method using multi wall carbon nanotube (MWCNT) coated with dithiooxamide as nanostructure sorbent has been effectively established for extraction and pre-concentration of trace amounts of cobalt ions before their determination by FAAS (flame atomic absorption spectrometry). Modified MWCNT was synthesized by the reaction of dithiooxamide with functionalized MWCNT. Initially, the surface of MWCNT was oxidized by a mixture of nitric and sulfuric acid and then was functionalized using thionyl chloride, following the ligand was attached to the MWCNT. The properties of nanostructure sorbent were characterized by SEM, BET, TGA, elemental analysis CHNS and FT-IR techniques. Some effective parameters on extraction and complex formation, such as pH, modified MWCNT dosage, concentration and type of eluent, contacting time, salt effect and sample volume have been optimized. We achieved the calibration graph in linear range of 3-2000 ng mL(-1) with limit of detection (LOD) of 0.64 ng mL(-1). Relative standard deviation (RSD) for Co (II) ions is calculated to be 2.2%. The projected technique has been used to assay of cobalt ions at ng mL(-1) levels in real samples such as tomato, potato, wheat flour, red beans, oat, tap water, river water and seawater with suitable fallouts.