Determination of cobalt in natural water samples after separation and preconcentration by dispersive liquid-liquid microextraction based on the solidification of floating organic drop

A simple، rapid and environmentally friendly method has been developed for the determination of cobalt ions in water samples by dispersive liquid–liquid microextraction based on the solidification of floating organic droplet (DLLME-SFO) coupled with flame atomic absorption spectrometry (FAAS). In this method، cobalt was complexed with 2-nitroso-1-naphthol and extracted into a small volume of 1-dodecanol، which is of low density، low toxicity and proper melting point near room temperature. Several variables that affect the extraction efficiencies، including pH، concentration of chelating agent، type and volume of the extraction solvent and dispersive solvent، extraction time and salt addition، were investigated and optimized. Under the optimized conditions، the limit of detection was 1. 6 µg L−1 with a preconcentration factor of 25 for 25 mL of sample. The proposed method has been successfully applied for the determination of cobalt in real water samples.