Vortex-assisted low density solvent and surfactant based dispersive liquid-liquid microextraction for sensitive spectrophotometric determination of cobalt.

This study describes the development of vortex-assisted low density solvent and surfactant based dispersive liquid-liquid microextraction (VALS-DLLME) for Co(ii) prior to its spectrophotometric detection. The method consisted of the complexation of Co(ii) with pyrocatechol violet (PV) followed by the preconcentration of the Co(II)-PV complex using VALS-DLLME and then an absorption measurement at 600 nm. The optimum conditions for complex formation were a 1 : 3 mole ratio of Co(ii) and PV at pH 7.5, while the conditions for VALS-DLLME were 300 μL 1-dodecanol as extraction solvent, and 300 μL acetonitrile as dispersive solvent under a vortex for 20 s with the addition of cationic surfactant (0.02 mmol L CTAB). Under the optimum conditions, good linearity was in the range of 0.1-10 mg L, the enrichment factor (EF) was 13.5 and the low limit of detection (LOD) was 0.04 mg L. The method was applied to the analysis of Co(ii) in water, green leaf vegetable and vitamin B samples. The proposed method provided good recoveries in the range of 86-104%, which were comparable to those obtained from flame atomic absorption spectrophotometry.