THE APPLICATION OF 4- (2-PYRIDYLASE)RESORCIN FOR EXPRESS DETERMINATION OF LEAD IN MEDICINAL PREPARATIONS
A new test method for determining lead (II) in medicinal plant raw materials and medicinal herbal preparations using an indicator plate immobilized with 4-(2-pyridylazo)resorcinol solution has been developed. Additional processing of the plate with 1 M sodium tartrate solution allows determinating of lead (II) in the presence of not more than 30.0 μg cadmium (II) and mercury (II) in the sample. The acidity required for the test reaction (pH 10.0) is created directly during the sample preparation. Direct processing of the test plate with a buffer solution facilitates the occurrence of side processes namely the formation of poorly soluble bases that generally makes it difficult to fix the intensity of its color. In addition, in order to avoid the occurrence of adverse reactions, it was sealed in a water-gas-tight material. The color of the indicator plate immersed in the analyzed solution develops within 2-5 minutes and varies depending on the xenobiotic content from red-orange to brown-orange. Moreover, the quantitative course of test reaction directly depends on the concentration of the reagent deposited on the indicator plate. As a result of the conducted research, the metrological characteristics of the developed test method have been established, namely, the interval of unreliability of lead (II) detection (0.060 ÷ 0.10μmol), detection limits (0.093 μmol) and visual determination (0.159 μmol). Such a narrow interval of unreliability (0.67) indicates good analytical characteristics of the selected test reaction and the stability of the test system to external influences. Due to the fact that the limit of visual determination is slightly higher than the maximum permissible lead content (II) for medicinal plant raw materials and medicinal herbal preparations (OFS.1.5.3.0009.15), the developed test method can be recommended only for the detection of xenobiotics in the analyzed samples. Testing of methodology was carried out on samples of medicinal plant raw materials and medicinal herbal preparations of industrial production. Based on the results of the determination, it was established in the presence of lead trace in all analyzed samples. The reliability of the obtained results was confirmed by the results of determination of xenobiotics by atomic absorption spectrometry with electrothermal atomization (OFS.5.5.000.0009.15). Thus, the developed method for determining lead is characterized by simplicity of the experiment, it does not require expensive equipment that allows it to be used in a conventional control and analytical laboratory.