Trends in sorption preconcentration combined with noble metal determination.

Nowadays much attention is being paid to the determination of trace amounts of noble metals in geological, industrial, biological and environmental samples. The most promising techniques, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS) are characterized by high sensitivity. However, the accurate determination of trace noble metals has been limited by numerous interferences generated from the presence of matrix elements. To decrease, or eliminate, these interferences, the sorption preconcentration of noble metals is often used prior to their instrumental detection. A great number of hyphenated methods of noble metal determination using sorption preconcentration have been developed. This review describes the basic types of available sorbents, preconcentration procedures and preparations of the sorbent to the subsequent determination of noble metals. The specific features of instrumental techniques and examples of ETAAS, FAAS, ICP-AES, ICP-MS determinations after the sorption preconcentration of noble metals are considered. The references cited here were selected mostly from the period 1996 - 2006.     

Sorption preconcentration in combined methods for the determination of noble metals

Combined methods for the determination of noble metals with the use of sorption preconcentration with complexing, anion-exchange, and other sorbents are reviewed. Characteristics of sorbents, techniques of sorption preconcentration, and techniques for the preparation of a concentrate for determination are considered. Features of instrumental methods for the determination of noble metals in the analysis of different materials are discussed. Examples of the use of sorption preconcentration in combined methods for the determination of noble metals are given from publications between 1996–2005.     

Preconcentration of noble metals with the POLYORGS 4 complexing sorbent under the action of microwave irradiation

The sorption of Au(III), Pd(II), Pt(IV), Rh(III), and Ir(IV) with the POLYORGS 4 complexing sorbent in the static mode was studied at room temperature and on thermal and microwave heating. It was demonstrated that the sorption of noble metals from 1 M HCl and 1 M HNO₃ solutions can be substantially accelerated under the action of microwave irradiation. Based on the obtained data, the conditions of the group preconcentration of noble metals for their subsequent determination by the ETAAS and ICP AES methods were selected. The preconcentration procedure was used for the analysis of certified reference material SARM-7B (platinum-containing ore), VT-1 (copper-nickel sulfide ore), and the alloy of copper with noble metals.     

Microwave preparation of natural samples to the determination of mercury and other toxic elements by atomic absorption spectrometry

Methods have been developed for the preparation of samples containing organic matrices (natural high-color waters, soils, bottom sediments, aquatic organism tissue) to the determination of mercury and other toxic elements (As, Cd, Pb, Se) by different procedures of microwave digestion under elevated pressure (closed systems, vessels with partial removal of the gas phase). It is found that, under optimal oxidative and temperature-time conditions, the partial removal of the gas phase does not lead to losses of volatile elements if sample portions under 2 g are used. The duration of preparation of a series of samples does not exceed 40 min. The detection limits for mercury in the cold vapor atomic absorption spectrometry and for Cd, Pb, As, and Se by electrothermal atomic absorption spectrometry are 5 and 0.13, 6, 13, and 13 μg/kg, respectively. The accuracy of determination is confirmed by the results of analysis of certified reference materials of water and plant materials and also by the standard addition method. The selected conditions of preparation of sludge samples have ensured the determination of mercury by the cold vapor atomic absorption spectrometry in drinking, natural, and sewage waters with a detection limit of 0.07 μg/L.     

A new combined ETAAS method for the determination of platinum, palladium, and gold traces in natural samples

A new combined method is developed for determining trace platinum, palladium, and gold in natural materials of complex composition. The method involves sorption preconcentration with solid-phase extractants obtained by impregnating polymer supports (hypercrosslinked and highly crosslinked polystyrene resins) with an imidazolium ionic liquid (1-hexadecyl-3-methylimidazolium bromide), elution with acetone under normal conditions or with a solution of thiourea in 1 M HCl under microwave heating, and the ETAAS determination of analytes in the eluate. The efficiency of the method is confirmed by the analysis of various ores and rocks.     

Effect of Microwave Irradiation on the Cross-Linking of Polyvinyl Alcohol

The possibility of dehydration (cross-linking) of polyvinyl alcohol upon microwave irradiation of thin polymer films was examined. The properties of polyvinyl alcohol samples treated by convection heating and irradiation were compared. Immobilization of polyvinyl alcohol on polymer matrices by microwave irradiation was studied.     

Preparation of Binuclear Rhodium(II) Tetraacetate (Initial Compound for the Coulometric Determination of Rhodium) under the Action of Microwave Radiation

A rapid method is proposed for the preparation of binuclear rhodium(II) tetraacetate [Rh₂(OAc)₄(HOAc)₂] under the action of microwave radiation. This complex is potentially suitable for the coulometric determination of rhodium. The mechanism of the redox process Rh₂(III, II) Rh₂(II, II) in acetic acid solutions of this complex has been characterized by cyclic voltammetry, controlled-potential coulometry, and spectrophotometry.     

Microwave sample preparation for geochemical and ecological studies

The review considers the general principles and current status of microwave sample preparation and the areas of its application to solving geochemical and ecological problems.