A simple, rapid, and sensitive anodic stripping voltammetric method for the determination of Pt (IV) is described. It is based on depositing an intermetallic indium-platinum alloy phase on the surface of a modified graphite electrode, and recording the oxidation peak of indium from that alloy phase with the help of linear scan voltammetry. A systematic study of the behavior of different In-Pt phases revealed that the peak potential of indium oxidation from the different phases can be explained on the basis of simple thermodynamic considerations. Different alloy phases have characteristic peak potentials. For the purpose of analysis, it is possible to choose such conditions that only one specific alloy phase forms, viz. PtIn. This is the case for a concentration (milligrams per liter) ratio of In (III)/Pt(IV)050,000:1, at least.
Nowadays the actual problem of geochemistry is a deep and complex processing of mineral raw materials. Data on the quantitative content of precious and rare metals in various types of ores and rocks are necessary. It stimulates the development and improvement of chemical analytical methods for determination of these elements. Such methods are not applicable without sample preparation stage. Preparation of samples for analysis is the decomposition and preconcentration of rare and precious metals from matrix of mineral raw materials. The sample preparation schemes of platinum, palladium and rhenium are described in this paper.
It is shown that platinum can be determined by anodic stripping voltammetry at the peak of selective electrooxidation of copper from intermetallic phase with platinum of Cu 3 Pt composition. The composition of intermetallic copper-platinum phase formed on the electrode during pre-electrolysis was calculated on the amount of potential displacement (ΔЕ) of copper electrooxidation.
Electrolytic deposit of indium, platinum and platinum-indium alloy on the surface of graphite electrodes has been studied using the scanning electron microscopy and the stripping voltammetry. The scanning electron microscopy method has revealed that platinum-indium alloy on the surface of the graphite electrode contains indium, platinum and chlorine. But platinum is unable to be determined on the surface of the graphite electrode without a metal activator due to its precipitation in very small quantities. Under the anodic oxidation of indium-platinum precipitation, the anodic peaks caused by the selective electro-oxidation of indium from the intermetallic compounds with platinum are observed on the current-voltage curves. Wherein, platinum remains on the electrode surface, and can be oxidized from the electrode at the potentials of the electrode purification (more than 1 V).
In spite of selectivity of platinum and rhenium stripping voltammetry analysis techniques, it is very difficult to identify them in the presence of other metals. This manuscript reports on the stripping voltammetric determination of platinum and rhenium in the presence of other metals. The effect of accompanying elements on the electrochemical oxidation processes of platinum and rhenium has been described. It has been shown that it is possible voltammetric determination of platinum and rhenium after removal of interfering matrix components of mineral raw materials at the stage of sample preparation.
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