ATOMIC-ABSORPTION DETERMINATION OF COBALT IN TABLE SALT AND BRINES

The extraction of cobalt in the form of diethyldithiocarbamate with methyl isobutyl ketone and chloroform from sodium chloride solutions was investigated. It was found that the interfering effect of sodium chloride begins at 50 g/dm(3 )when using methyl isobutyl ketone, and at 90 g/dm(3) when using chloroform. It is shown that fulvic acids in concentrations above 12.0 mg/dm(3) underestimate the results of cobalt determination, which makes quantitative determination impossible without the destruction of soluble organic compounds. It is proposed to use ultrasound with a frequency of 18-44 kHz and an intensity of >= 5 W/cm2 for at least 60 s to destroy soluble organic substances of cobalt. It was found that when using the extraction system sodium diethyldithiocarbamate - methyl isobutyl ketone, the quantification limit of cobalt determination is 0.90 mg/kg, which is insufficient for the analysis of real objects of table salt. When using the extraction system sodium diethyldithiocarbamate - chloroform, the quantification limit of cobalt determination is 0.04 mg/kg, which is insufficient for the determination of cobalt in vacuum evaporated table salt. The influence of surfactant concentrations on the analytical signal value in the atomic absorption determination of cobalt was studied. It is shown that the maximum sensitivity of cobalt determination is achieved when using aqueous solutions of Triton X-100 (omega = 5 %). In this case, the sensitivity of cobalt determination increases by 1.53 times. A method for the determination of cobalt in table salt and brines has been developed. The limit of detection of cobalt is 0.026 mg/kg.