Simultaneous determination of nickel, cobalt and mercury ions in water samples by solid phase extraction using multiwalled carbon nanotubes as adsorbent after chelating with sodium diethyldithiocarbamate prior to high performance liquid chromatography

• Develop a new enrichment method for nickel (Ni2+), cobalt (Co2+) and mercury (Hg2+) with MWCNTs.
• Establish a simple and sensitive method for the simultaneous analysis of metal ions.
• Widen the applicability of MWCNTs in environmental field.

Multiwalled carbon nanotubes (MWNTs) have been widely used for the enrichment of trace important pollutants in environment because of its large specific surface area, high extraction efficiency, and easy operation. In this study, a solid phase extraction method was established to determine nickel (Ni2+), cobalt (Co2+) and mercury (Hg2+) ions using MWNTs as the adsorbent and sodium diethyldithiocarbamate (DDTC) as the chelating agent. The final analysis was performed on a high performance liquid chromatography (HPLC). The factors that may influence the extraction efficiency were optimized in detail including the type and volume of elution solvent, sample pH, volume of chelating agent solution, and volume of sample solution, etc. The experimental results indicated that good linear relationship between peak area and the concentration of the ions was achieved in the range of 0.1–100 μg L−1, 0.1–50 μg L−1, and 2.7–300 μg L−1 for Ni2+, Co2+, and Hg2+, respectively. The precision was determined by calculating the relative standard deviation (R.S.D.) values that were in the range of 6.2–11.7% under the optimal conditions. The detection limits of Ni2+, Co2+, and Hg2+ were in the range of 0.04-0.9 μg L−1 (S/N = 3). The presented method was applied for the determination of the metal ions mentioned above in real water samples, and satisfied results were achieved. All these indicated that proposed method will be a good alternative tool for monitoring the target ions in environmental samples in the future.