The main purpose of this study was the comparison of the results of quantification obtained via different sample preparation approaches such as microwave-assisted wet digestion (MAWD) and suspension preparation. Two total reflection x-ray fluorescence (TXRF) spectrometers equipped with Mo x-ray tubes were used to compare results obtained via two different paths of sample preparations which would further be compared to the conventional way of analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) including MAWD. Three dietary supplement samples with different sets and concentrations of elements were analyzed. The benefits and limitations of the simplified path of sample preparation were highlighted. A round-robin test between TXRF and ICP-OES was discussed. Accuracy as the percentage of recovery in all measurements ranged from 80 to 120. Precision for all results did not exceed 8% for TXRF and 5% for ICP-OES. Limits of quantification by TXRF are ranged from 1 to 0.01 mg/pill for different elements. It was shown that suspension preparation of samples might be a useful response to increasing demand for quality control of dietary supplements since it is less time consuming and cost efficient.

Описан способ пробоподготовки витаминно-минеральных комплексов (ВМК) для последующего определения элементного состава методом рентгенофлуоресцентного анализа с полным внешним отражением (РФА ПВО). Предложена подготовка малорастворимых образцов ВМК в виде суспензий в этиленгликоле, так как этот способ позволяет избежать сложной процедуры вскрытия образца, упростить и ускорить процедуру анализа. Для количественного определения использован способ внутреннего стандарта. Результаты определения методом РФА ПВО сопоставлены с данными атомно-эмиссионной спектроскопии с индуктивно связанной плазмой (ИСП АЭС) и с данными, представленными фирмами-производителями. Методом РФА ПВО никель в препарате «Мультимакс» на заявленном производителем уровне не обнаружен. Обнаружение никеля методом ИСП АЭС может быть вызвано его внесением в ходе длительной пробоподготовки при контакте раствора с элементами оборудования, изготовленными из нержавеющей стали. В образце ВМК «Дуовит» было отмечено незначительное содержание хрома и никеля по данным ИСП АЭС. Производителем эти элементы не были заявлены, и методом РФА ПВО не обнаружены. Метод РФА ПВО, хотя и обладает меньшими показателями сходимости по сравнению с широко распространенным методом ИСП АЭС, позволяет использовать значительно более простые методы пробоподготовки (растворение и суспендирование) и сократить время анализа в несколько раз.

Techniques to prepare samples of vitamin-mineral complexes (VMCs) for total reflection x-ray fluorescence (TXRF) analysis are described. Sample preparation of slightly soluble VMCs as suspensions in ethylene glycol is proposed because this method avoids complicated sample digestion and simplifies and accelerates the analytical procedure. The internal standard technique is used for quantitative determination. The results of TXRF determination are compared to those of inductively coupled plasma atomic emission spectrometry (ICP-AES) and to data provided by the manufacturers. Nickel in Multimax VMC was not detected by TXRF at the level declared by the manufacturer. Nickel detected by ICP-AES may be caused by its introduction during lengthy sample preparation where solutions contact stainless-steel equipment. Low contents of chromium and nickel are found in Duovit VMC by ICP-AES. These elements are not declared by the manufacturer and are not found by TXRF. Although TXRF has lower agreement factors than widely used ICP-AES, it uses a much simpler sample preparation technique (dissolution and suspension) and shortens the analysis time by several times.

Here we report formation of gold nanoparticles (GNPs) in micelles of polytyrosine-PEG copolymers that combine the properties of a reducer and a stabilizer. The size and properties of the GNPs were tailored by the excess chloroaurate over the copolymer. The latter quickly formed non-covalent complexes with HAuCl4 and then slowly reduced it to form GNPs. 3 Tyr residues are consumed by reduction of one mole of chloroaurate. The size of the GNPs was controlled by the [Tyr]/[Au(iii)] molar ratio. Small GNPs with D ≅ 8 nm were formed at [Tyr]/[Au(iii)] = 0.5-1.5. 90% of these small GNPs remained bound to the copolymer and could be stored in a lyophilized state. Such polypeptide-gold hybrid materials produced at [Tyr]/[Au(iii)] = 0.5 demonstrated high activity in the catalytic reduction of 4-nitrophenol by sodium borohydride. [Tyr]/[Au(iii)] = 5 led to the formation of large nanoplates (D ≅ 30-60 nm). Thus, in the polymer-based system the GNP size grew in line with the excess of the reducing agent in contrast to Turkevich synthesis of GNPs with citric acid, which also combines the functions of a stabilizer and a reducer. The difference results from the reduction of HAuCl4 in solution according to the Turkevich method and in the micelles of the amphiphilic polymer where the seed growth is limited by the amount of neighboring reducer.

Techniques for the determination of the elemental composition of dietary supplements (Multifort®, Komplivit®) are presented. It is proposed to use a state-of-the-art analytical method, total reflection X-ray fluorescence spectrometry. The differences in the sample preparation of encapsulated and not encapsulated dietary supplements are described. The effect of encapsulation on the results of the analysis is revealed. The results of qualitative and quantitative analysis are compared with the values certified by the manufacturing company.

Methods for the synthesis of polymer hydrogel–metal metamaterials based on polyvinyl alcohol and reduced Cu, Ag, Co, and Fe (or magnetite Fe 3 O 4 ) particles, including the stage of chemical or thermal reduction or chemical precipitation were proposed. The effect of the synthesis conditions on the size of metal or oxide particles and the regularity of particle distribution in the polymer was studied. The samples of composite materials synthesized under different conditions were characterized by nondestructive X-ray fluorescence and X-ray diffraction methods. An XRD study revealed that after the thermal reduction of Cu, Co, and Fe, the composite contained a significant amount of metal oxides. The optimum conditions for the synthesis of polyvinyl alcohol–magnetite metamaterials were found.

An algorithm for total reflection X-ray fluorescence analysis of samples containing significant amounts of light elements with Z < 11, which are difficult to detect, is proposed based on the use of X-ray fluorescence intensity ratios. Such relative signals are much less influenced by the actual shape of a specimen and its mass, thus providing more accurate results of analysis. A Rayleigh-to-Compton scattering intensity ratio depends on the light elements total content, which thus can be evaluated. That a theoretical calibration equation describing a dependence of the Rayleigh scattering intensity on the sample's mass can be applied to the sample mass determination is demonstrated. A fundamental parameter analysis algorithm is designed that minimizes a need for external or internal standards. Its validity is proved by analysis of highly mineralized water samples.

Glutathione-capped gold nanoclusters display polyanionic properties that are manifested in the interaction with cationic species. The nanoclusters form complexes with doxorubicin with effective dissociation constant about 10 µM that increased by an order of magnitude in the presence of 0.15 M NaCl confirming electrostatic character of binding. Adsorption of polylysine arose an increase in the fluorescence of gold nanoclusters due to aggregation induced emission enhancement effect. Fluorescence of the complexes increased several-fold upon addition of up to 1 M of KCl suggesting contribution of non-Coulombic forces in the stabilization of aggregates of gold nanoclusters.

A new approach for the direct determination of the elemental composition of copper–zinc ores by TXRF based on non-aqueous suspension preparation is proposed.

In this work, we report a technique of the self-formation of a nanonet of fluorinated carbon nanowires on the Si surface using a combined etching in fluorine-containing C4F8/Ar and SF6 plasmas. Using scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy, we show that after the etching of Si in the C4F8/Ar plasma, a fluorinated carbon film of nanometer-scale thickness is formed on its surface and its formation accelerates at elevated temperatures. After a subsequent short-term etching in the SF6 plasma, the film is modified into a nanonet of self-formed fluorinated carbon nanowires.

ABSTRACT The total reflection X-ray fluorescence determination of mercury(II) in drinking water at concentrations of 7 × 10−2 to 3.0 µg/L is reported. The mercury(II) preconcentration protocol includes directly suspended droplet microextraction with benzene as a molecular iodine complex. The proposed approach is highly selective. The elements Cr, Mn, Fe, Co, Ni, Zn, and Pb at concentrations up to 0.1 g/L did not interfere with the extraction of trace mercury(II). The method is characterized by high sensitivity (limit of detection of 21 ng/L) and suitable reproducibility (relative standard deviation of 0.12 for 100 ng/L). The accuracy of the results was confirmed by recovery and the method of standard addition.

A review of studies performed at the Division of Analytical Chemistry of the Department of Chemistry of Moscow State University on the determination of the elemental composition of solid samples of the metallurgical industry (coals, coke, copper–zinc ores) by total reflection X-ray fluorescence spectrometry, one of the newest and promising methods of chemical analysis, is presented. This direction is developed at the Division in the last five years. A possibility of the determination of the elemental composition of solid samples as suspensions using the available and safe reagents without sample decomposition is shown. Special attention is paid to the problems of sample preparation and also to the assessment of the effect of the conditions of sample preparation on the results of analysis. Approaches to the improvement of performance characteristics are proposed and the conditions of the preparation of suspensions are optimized.

Novel rapid determination of copper-zinc ore elemental composition by total reflection X-ray fluorescence (TXRF) is proposed. Approaches for solid state sample analysis by TXRF are provided. The sample preparation is chosen to obtain the suspensions in ethylene glycol. The optimum suspension preparation conditions (sample mass, volume of dispersion medium) and the measurement conditions (internal standard element, spectra acquisition time) were determined. The sedimentation stability of suspensions was studied. It was found that the suspensions remain stable for approximately 2min, which is sufficiently long for the sampling the suspension. The proposed technique allows determining the elemental composition of solid ore samples without sample digestion. The sample preparation time takes approximately 20min. The relative standard deviation of the analytical results did not exceed 10%.

A review of works of researchers of the Division of Analytical Chemistry of the Department of Chemistry of Moscow State University over the last 5 years in the total reflection X-ray fluorescence analysis of natural and drinking waters is presented. The advantages of the proposed methodological approaches to the sorption and extraction X-ray fluorescence determination of metal ions in waters are described. Various methods of the improvement of the performance characteristics of the results of analysis are discussed and compared (first of all, sensitivity of determination).

A method is proposed for determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water by means of total-reflection X-ray fluorescence analysis. In this work, the combined technique of preconcentration of rare earth ions is used. This technique consists of coprecipitation of metal hydroxides on the collector (iron (III) hydroxide) and dispersive liquid–liquid microextraction of their complexes with 1-(2-pyridylazo)-2-naphthol by chloroform in the presence of ethanol. The use of the developed hybrid approach allows simultaneous determination of the mentioned metals in mineral water in the range n(10–2–101) μg/L. The results of analysis of Arkhyz and Rychal-Su mineral waters by the proposed extraction–X-ray fluorescent method are confirmed by the literature data, obtained by inductively coupled plasma mass spectrometry.