EXTRACTION-ABSORPTIOMETRIC DETERMINATION OF CADMIUM BY RHODAMINE DYES IN TOBACCO AND MILK PRODUCTS

Abstract

Cadmium is a toxic and cumulative heavy metal that poses a threat to human health even in low concentrations. Cadmium poisoning mainly occurs as a result of its use in industry. Cadmium enters the environment during ore processing, waste incineration- plastics, cadmium-nickel batteries, etc., tobacco smoke and transport.

Despite the emergence of modern methods of element analysis, the extraction-absorptiometric method remains relevant due to its accessibility and high sensitivity.The advantage of using basic dyes is that they form ionic associates (IA) with anionic metal complexes, which are extracted with organic solvents, leaving excess dye in the aqueous solution. This make the method highly sensitive and selective.

The interaction of the cadmium iodide anion complex with the cation of rhodamine dyes—rhodamine S (RS) and rhodamine 6G (R6G) has been studied. The ionic associate formed is extracted by a single extraction with butylacetate (when using RS) and a binary mixture of dichloroethane and toluene (1:3) (when using R6G).The optical density of the organic phase was measured at wavelengths λ=555 nm (RS) and λ=515 nm (R6G). The optimal conditions for the formation and extraction of IA have been established: acidity of the aqueous phase; concentrations of dyes, potassium iodide, cadmium, etc. The compliance with the basic law of photometry is observed in the cadmium concentration interval of 0.625–10 μg/ml (for RS) and 0.65–10 μg/ml (for R6G). The molar absorption coefficient is 62300±400 l·mol^-1·cm^-1 and 28700±300 l·mol^-1·cm^-1for RS and R6G, respectively.The composition of cadmium IA was determined using spectrophotometric methods: Asmus direct line and equilibrium shift. The molar ratio of the dye cation to the cadmium iodide complex (for two dyes) is 1:1.

Our direct extraction-absorptiometric method was used to determine cadmium in tobacco and milk products.