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A possibility of using a monitor calibrator for the determination of luminescent compounds is shown on an example of quinine. The determination is based on the irradiation of a sample with broadband radiation in the visible and near UV spectral regions from a built-in source exciting phosphor molecules and the simultaneous registration of the radiation incident on the detector. Measurement conditions are selected. Quinine can be determined in the range of 60-750 [micro]M, the limit of detection is 20 [micro]M. The determination is not affected by common inorganic ions, as well as sweeteners and acidity regulators present in many beverages. The developed method of determination is applicable to the analysis of carbonated drinks and drugs. Compared to a traditional spectrofluorimeter, monitor calibrator is characterized by compactness, mobility, ability of detecting luminescence in cuvettes of various sizes and shapes, and lower cost., Author(s): M. V. Gorbunova [sup.1] , T. A. Terentev [sup.1] , V. V. Apyari [sup.1] , S. G. Dmitrienko [sup.1] , Yu. A. Zolotov [sup.1] [sup.2] Author Affiliations: (1) grid.14476.30, [...]

Possibilities of using analytical systems based on silver triangular nanoplates for the spectrophotometric determination of reductants are studied. It is found that the interaction of silver triangular nanoplates with L-ascorbic acid in the presence of silver(I) nitrate is accompanied by a bathochromic shift and an increase in the intensity of the surface plasmon resonance band of nanoparticles, which can be used as the basis for methods for determining reductants. The proposed interaction mechanism includes the reduction of Ag.sup.+ ions to metallic silver under the action of an analyte and its deposition on the surface of nanoparticle seeds. The effects of pH, interaction time, and concentrations of reagents and foreign compounds on the value of the analytical signal are studied. The limit of detection for L-ascorbic acid under the selected conditions is 0.5 mg/L, the analytical range is 1.7-60 mg/L. The approach proposed in this paper was applied to the determination of L-ascorbic acid in leafy green tea and apple juice., Author(s): A. A. Furletov [sup.1] , V. V. Apyari [sup.1] , A. V. Garshev [sup.1] [sup.2] , S. G. Dmitrienko [sup.1] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, Department [...]

We proposed a procedure for the rapid sample preparation of food samples for the determination of nitrofuran metabolites in them by HPLC-MS/MS, using 5-nitro-2-furaldehyde as a new derivatizing agent. Meat samples from broiler chickens treated with nitrofurans for 10 days were used to demonstrate that the time of hydrolysis-derivatization in a thermostated ultrasonic bath could be significantly shortened by raising temperature to 80°C and increasing the concentration of hydrochloric acid to 0.5 M. Metabolites of Furaltadone, Furazolidone, Nitrofurantoin, and Nitrofurazone in chicken meat, liver, stomach, and heart are determined using the developed procedure and an official method. The proposed method ensures the quantitative isolation of metabolites., Author(s): A. O. Melekhin [sup.1] [sup.2] , V. V. Tolmacheva [sup.1] , Yu. N. Kholyavskaya [sup.2] , E. S. Sedykh [sup.2] , S. G. Dmitrienko [sup.1] , V. V. Apyari [...]

5-Nitro-2-furaldehyde is proposed as a new derivatizing agent for determining four nitrofuran metabolites: 3-amino-2-oxazolidinone, 3-amino-5-methylmorpholino-2-oxazolidinone, 1-aminohydantoin, and semicarbazide in chicken eggs by HPLC with tandem mass spectrometric detection. The derivatization products were identified; they are the initial nitrofurans: furazolidone, furaltadone, nitrofurantoin, and nitrofurazone, respectively. Sample preparation includes acid hydrolysis, derivatization, fat removal by hexane extraction, and the further purification of the extracts on cartridges packed with Diapak P-3 hypercrosslinked polystyrene. The method ensures the quantitative isolation of metabolites (recovery rates are 95 to 106%) and good reproducibility (RSD [less than or equal to] 13%)., Author(s): A. O. Melekhin [sup.1] [sup.2], V. V. Tolmacheva [sup.1], E. G. Shubina [sup.2], S. G. Dmitrienko [sup.1], V. V. Apyari [sup.1], A. I. Grudev [sup.2], Yu. A. Zolotov [sup.1] [...]

Hypercrosslinked polystyrene is proposed for the multicomponent solid-phase extraction of residues of 63 veterinary preparations from various classes (sulfonamides, tetracyclines, quinolones, amphenicols, nitroimidazoles, [beta]-lactams, macrolides, lincosamides, and pleuromutilins) in their determination in chicken meat by HPLC-tandem mass spectrometry. Sample preparation includes the extraction of analytes with a McIlvaine buffer solution, fat removal by extraction with hexane, and the further purification of the extracts on cartridges with hypercrosslinked polystyrene. The method ensures the quantitative extraction of analytes (recovery rates are from 83 to 117%) and good reproducibility (RSD [less than or equal to] 12%). Veterinary preparations were identified by the exact masses of analyte ions formed in electrospray ionization on switching positive and negative polarity. The matrix effect for all veterinary drugs was below 20%. The determination was carried out by the method of matrix calibration; the limits of detection and determination were 0.01-0.3 and 0.02-1 ng/g, respectively. An analysis of contaminated chicken meat samples showed that the results are in satisfactory agreement with the data obtained by the methods adopted in the Russian Federation for the determination of various groups of antibiotics., Author(s): A. O. Melekhin [sup.1] [sup.2], V. V. Tolmacheva [sup.1], E. G. Shubina [sup.2], S. G. Dmitrienko [sup.1], V. V. Apyari [sup.1], A. I. Grudev [sup.2] Author Affiliations: (1) grid.14476.30, [...]

Single-drop microextraction (SDME) and hollow-fiber membrane microextraction (HFME) belong to methods of the liquid-phase microextraction preconcentration of organic compounds. These methods are characterized by the low consumption of organic solvents, high preconcentration factors, simplicity, low cost, ease of combination with various chromatographic methods; processes of preconcentration and sample injection are combined in a single device. Since the emergence of SDME (1996) and HFME (1999), a large number of versions have been developed that differ in the preconcentration technique, nature of the extractants used, and combinations with methods for the subsequent determination of the preconcentrated substances. The popularity of these methods among the analysts is evidenced by many reviews that we have summarized in this publication., Author(s): S. G. Dmitrienko [sup.1], V. V. Apyari [sup.1], V. V. Tolmacheva [sup.1], M. V. Gorbunova [sup.1] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, Department of Chemistry, Lomonosov Moscow [...]

A chemical method is proposed for obtaining a nanocomposite based on gold nanoparticles (AuNP) and polyurethane foams (PUF). It includes the sorption of a reducing agent, sodium borohydride, on PUF from a solution containing sodium hydroxide as a stabilizer and cetyltrimethylammonium bromide as an ion-pair reagent, and the subsequent interaction of the modified polymer with chloroauric acid, leading to the formation of a colored nanocomposite. A possibility of using the process of the formation of a nanocomposite based on AuNP and PUF for the determination of melamine in milk powder and milk powder substitute by diffuse reflectance spectroscopy is evaluated. It is found that melamine affects the formation of this nanocomposite, causing a decrease in the intensity of the surface plasmon resonance band of gold nanoparticles in the material. It is proposed to use this effect for the determination of melamine by diffuse reflectance spectroscopy. The influence of the interaction time, the pH of the solution, and the concentration of chloroauric acid on the analytical signal, as well as the interfering effect of amino acids in the determination of melamine, are investigated. Under the chosen conditions, the limit of detection for melamine was 0.2 mg/L., Author(s): A. I. Isachenko [sup.1], A. O. Melekhin [sup.1], V. V. Apyari [sup.1], P. A. Volkov [sup.2], S. G. Dmitrienko [sup.1] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, Lomonosov [...]

Published data on various versions of the homogeneous liquid-liquid microextraction (HLLME) of organic compounds are generalized and systematized, and a classification of these versions is given. The main HLLME procedures are discussed. Examples of the application of HLLME to the separation of organic compounds in the analysis of environmental samples, food products, and biological fluids are given., Author(s): S. G. Dmitrienko [sup.1], V. V. Apyari [sup.1], M. V. Gorbunova [sup.1], V. V. Tolmacheva [sup.1], Yu. A. Zolotov [sup.1] [sup.2] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, [...]

Dispersive liquid-liquid microextraction (DLLME) is one of the most promising methods of the microextraction preconcentration of organic compounds. This method is eco-friendly, simple, and universal; in comparison with conventional extraction, the consumption of the reagents and solvents, the time of extraction, and the cost of analysis in this method are reduced. For a short time from the moment of the appearance of DLLME in 2006, analysts developed numerous versions, differing by the method of dispersion, the nature of the extractant and by combinations with other methods of sample preparation and methods of the subsequent determination of the preconcentrated substances. The popularity of the method among the analysts is attested in a great number of reviews summarized in this publication., Author(s): S. G. Dmitrienko [sup.1], V. V. Apyari [sup.1], V. V. Tolmacheva [sup.1], M. V. Gorbunova [sup.1] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, Department of Chemistry, Lomonosov Moscow [...]

A method is proposed for the determination of cysteine in an aqueous solution by its effect on the formation of gold nanoparticles on the surface of polyurethane foams. The method is based on the interaction of in situ formed gold nanoparticles with cysteine, which results in their stabilization in solution and in a decrease in the color intensity of the nanocomposite detected by diffuse reflectance spectroscopy. The effect of the concentration of the precursor, aurichlorohydric acid, contact time of phases, and the pH of the solution on the sensitivity of cysteine determination is studied. Under the selected conditions, the limit of detection for cysteine was 0.36 [mu]g/mL. A possibility of using the proposed method for the determination of cysteine in brewer's yeast is demonstrated., Author(s): A. I. Isachenko [sup.1], V. V. Apyari [sup.1], P. A. Volkov [sup.2], S. G. Dmitrienko [sup.1], Yu. A. Zolotov [sup.1] [sup.3] Author Affiliations: (1) grid.14476.30, 0000 0001 2342 9668, [...]

The use of hypercrosslinked polystyrene for the group sorption preconcentration of catecholamines is proposed. The conditions for the preconcentration of noradrenaline, adrenaline, and dopamine are optimized: a microcolumn (10 x 6 mm), mass of adsorbent 0.03 g, 25 mL of solution (pH ~ 8.5), and transmission rate of the solution 1.0 mL/min. Compounds were desorbed with 1 mL of 6 M acetic acid and determined in the eluate by reversed-phase HPLC with an amperometric detector (E = 0.8 V). Adsorption preconcentration ensures the reduction of the limits of detection for catecholamines by more than 20 times. The limits of detection were 0.7 ng/mL for dopamine and 1 ng/mL for noradrenaline and adrenaline. The procedure was applied to the analysis of model mixtures based on urine., Author(s): V. V. Tolmacheva [sup.1] [sup.2], D. I. Yarykin [sup.1], M. V. Gorbunova [sup.1], V. V. Apyari [sup.1], S. G. Dmitrienko [sup.1], Yu. A. Zolotov [sup.1] [sup.2] Author Affiliations: (1) [...]