Development and Application of Temperature-Induced Dispersive Solid Phase Extraction for Preconcentration and Determination of Cobalt Ions in Water and Food Samples

This work describes the development of temperature-induced dispersive solid phase extraction (TI-DSPE) for the isolation and measurement of cobalt in food and water samples. The concentration of the preconcentrated cobalt ions was determined using flame atomic absorption spectrometry (FAAS). In TI-DSPE, the dispersion of the sorbent occurs by varying the temperature. The cobalt was complexed with 1-nitroso-2-naphthol and extracted with finely dispersed benzoic acid particles at 60 °C. The extraction efficiencies parameters were assessed and optimized, such as the mass of benzoic acid, dissolution temperature, solution pH, centrifugation conditions, and ionic strength. In the optimum conditions, the analytical curve was linear from 2.0 to 150.0 µg L−1, the limits of detection and quantification were 0.55 and 1.83 µg L−1 respectively, and the preconcentration factor was 50. Ten repeated measurements at 50.0 µg L−1 yielded a relative standard deviation (RSD) of 2.6% (n = 10). High extraction recoveries (96.5–102.5%) were obtained from the analysis of real samples. The validity of the developed procedure was confirmed by analyses of certified reference materials (QC-1187 and SPS-SW2). The results demonstrated that the developed method was simple, efficient, and cost-effective.