A rapid and sensitive method for the differential determination of Cr"' and Crv' in river water is described. Chromium species can be separated by sorption on a polymeric Detata sorbent containing conformationally flexible aminocarboxylic groups. Preconcentration using either static or dynamic conditions is possible. Microwave heating energy was used to promote the sorption. Quantitative sorption of CrI" was achieved at pH 7, and that of Crvl at pH 3; hence, complete isolation of the two forms of Cr is possible. The optimum conditions (flow rate and sorbent volume) for sorbent extraction of Cr"' and Crvl were evaluated. The technique developed is based on the ability of the sorbent to preconcentrate Cr rapidly under dynamic conditions in the presence of a microwave field. Determination of Cr by electrothermal atomic absorption spectrometry is possible either after desorption or directly in the sorbent phase. The detection limit (based on the 3s criterion) is 30 ng 1-1; the technique is characterized by high reproducibility.

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New ecological and geochemical problems call for the sophistication of techniques for analyzing platinum samples [1]. Special attention is given to the search for and study of new potential sources of nontraditional platinum raw materials among organic substances at different stages of metamorphism (coals, carbonaceous shales, iron-manganese concretions, etc.) [2,3]. The study of the anomalous iridium distribution in some sedimentary rocks and the control of environmental contamination with platinum, iridium, and rhodium because of the use of combustion catalysts are also urgent tasks [4]. These problems are complicated by the test samples including high concentrations of organic substances and low concentrations of noble metals, which occur as various species insufficiently studied yet [5,6].The most common natural species of noble metals are native metals (including invisible colloidal metals), as well as intermetallides, sulfides, tellurides, selenides, arsenides, and antimonides [4,7]. Being siderophils, noble metals form compounds with iron and iron-group elements, particularly chromites. In carbon-containing natural samples, organic compounds of noble metals can also be found, along with the most common native species and solid solutions (e.g., platinum-copperiron) [2,6]. The ecological contamination with platinum and palladium is usually due to the presence of metal nanoparticles in dust and soil [8]. In at least the two latter cases, acid decomposition can be the most efficient method for solubilizing noble metals (provided the complete oxidation of the organic matter).Inductively coupled plasma-mass spectrometry (ICP-MS) (including its isotopic dilution version), electrothermal atomization-atomic absorption spectrometry (ETA-AAS), and inductively coupled plasma-atomic emission spectrometry (ICP-AES) offer most promise for the instrumental determination of trace noble metals [4,5,[8][9][10]. The potentials of each method used in the combined analytical schemes depend on the analyte nature and concentration, as well as on the presence of interfering matrix components, which affect the choice of the determination parameters.The possibilities of different instrumental methods in determining noble metals, as found from the generalized data of some analytical laboratories, are presented in Table 1 [11]. It can be seen that the actual detection limits for noble metals are relatively similar. At the same time, each method has its own unique features; these will be considered below.In spite of the high tolerance for the matrix compositions of test solutions and high efficiency of multielement determination, the ICP-AES is insufficiently sensitive for the direct determination of noble metals in solutions after the decomposition of most of the natural samples. Hyphenated techniques involving the separation of matrix components allow ICP-AES to be used for determining trace noble metals, although some problems arose. For example, the determination of gold is characterized by a significant and rapidly appearing memor...