Determination of Trace Levels of Nickel and Manganese in Soil, Vegetable, and Water

A simple and reliable method for rapid and selective extraction and determination of trace levels of Ni2+ and Mn2+ was developed by ionic liquid (IL) based dispersive liquid-liquid microextraction coupled to flame atomic absorption spectrometry (FAAS) detection. The proposed method was successfully applied to the preconcentration and determination of nickel and manganese in soil, vegetable, and water samples. After preconcentration, the settled IL-phase was dissolved in 100 mu L of ethanol and aspirated into the FAAS using a home-made microsample introduction system. Injection of 50 mu L of each analyte into an air-acetylene flame provided very sensitive spike-like and reproducible signals. Effective parameters such as pH, amount of IL, volume of the disperser solvent, concentration of the chelating agent, and effect of salt concentration were inspected by a (2(5-1)) fractional factorial design to identify the most important parameters and their interactions. Under optimum conditions, preconcentration of 10 mL sample solution permitted the detection of 0.93 mu g L-1 Ni2+ and 0.52 mu g L-1 Mn2+ with enrichment factors 77.2 and 82.6 for Ni2+ and Mn2+, respectively. The accuracy of the procedure was evaluated by analysis of a certified reference material (CRM TMDW-500, drinking water).