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

Abstract

The heavy metal cadmium is one of the most dangerous toxicants in the environment. Regardless of the aggregate state, cadmium compounds are poisonous and have the ability to accumulate in plants and a human and animal organisms.

Cadmium pollutes the environment through its use in mining and metallurgical industries, in the manufacture of pigments and plastic stabilisers, as well as production of nickel-cadmium batteries. In addition, high concentrations of cadmium are found in tobacco smoke. Therefore, the control of its content in industrial facilities and in the environment is an important and actual task for analytical chemistry.

Modern methods of analysis do not always allow to solve this problem due to the complexity of sample preparation and low availability of equipment. The proposed extraction-absorption method with the use of basic dyes makes it possible to determine the trace amounts of elements without preliminary concentration and separation from accompanying ions. Thus the method becomes more sensitive and selective.

The interaction of cadmium iodide anion complex (׀׀) with thiazine dye cation ─ tetramethylthionine has been studied. The ionic associate formed is extracted by a single extraction with a mixture of dichloroethane and toluene (1:3). The optimal conditions of extraction was established: acidity of the aqueous phase; concentration of dye, potassium

iodide, cadmium, etc. The compliance with the basic law of photometry is observed in the cadmium concentration interval of 0.625…12,5 µg/ml. The molar absorption coefficient is 82500±500 l·mol^-1·cm^-1. The composition of cadmium ionic association is established by spectrophotometric methods: Asmus direct line and equilibrium shift.

The method is applied for determination of cadmium in tobacco and milk products.

The proposed method is available for use in factory laboratories and daily analysis.