Journal of Analytical Chemistry (v.63, #9)

Studying the dependence of the representative weight of geological samples of gold-containing ores on their particle size by V. A. Shvetsov; N. V. Adel’shina; V. V. Pakhomova; N. B. Kosheleva; L. A. Bezrukova (824-826).
The dependence of the representative weight of a geological sample of quartz sulfide gold-containing ores on their particle size is studied. It is shown that the weight of the furrow samples selected in the chemical assay of gold-containing ores of the first group can be reduced two-to threefold.

Identification problems in the analysis of complex ion mixtures using the example of fumarol gases by N. K. Kolotilina; E. A. Polyntseva; A. M. Dolgonosov; M. E. Zelenskii (827-831).
Problems of identifying ion forms of elements in the analysis of complex natural objects by ion chromatography are considered. A method is proposed for finding the conditions of ion separation using the possibilities of the IONCHROM software; this allows for a significant reduction in the labor intensity of the analysis. The example of determining the anionic composition of a geochemical sample is given.

The complexation of molybdenum(VI) with bis(2,3,4-trihydroxyphenylazo)benzidine (H6L) is studied in the presence of 1,10-phenanthroline. A mixed-ligand complex formed with a molar component ratio of 2: 2: 4. The maximum absorbances of the binary and mixed-ligand complexes are observed at 437 and 426 nm, and their molar absorbance coefficients are (9.02 ± 0.02) × 104 and (10.01 ± 0.01) × 104, respectively. It is found that 1,10-phenanthroline affects H6L and improves the complexation characteristics. A procedure is developed for the photometric determination of molybdenum(VI) in seawater after preconcentration.

Argon-stabilized U-shaped DC arc with a system for aerosol introduction was used for the determination of As, Fe, Hg, Mn, and Pb. By applying a computer program performing a time integration of the registered signals and by optimizing the working conditions of an U-shaped arc plasma, the detection capability for As, Fe, Hg, Mn, and Pb was improved, which contributed to the lowering of the detection limits. The lowest detection limits for Fe, Mn, and Pb were achieved during an integration time of 20 s, and for As and Hg during an integration time of 30 s, and their values were 1.1, 0.1, 0.9, 15, and 2.6 ng/mL, respectively. The detection limits obtained by our method with optimal integration times were compared with the detection limits obtained using other methods: inductively coupled plasma-atomic emission spectrometry (ICP-AES), directly coupled plasma-atomic emission spectrometry (DCP-AES), microwave-induced plasma-atomic emission spectrometry (MIP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), and an improved thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS).

A new luminescence method for determining dysprosium in the presence of terbium by S. B. Meshkova; A. V. Kiriyak; M. P. Tsvirko; V. P. Gorodnyuk (840-843).
The new luminescence method for determining dysprosium in the presence of terbium is developed based on the difference in the lifetimes of dysprosium and terbium in complexes with 3-(6-benzodioxanyl)pyrazole-5-carboxylic acid (τ = 6 and 910 μs, respectively). The possibility of determining the short-lived and weakly luminescent dysprosium(III) ion in the presence of long-living and intensively luminescent terbium(III) was demonstrated for the first time using time-resolved luminescence. The developed method was used to determine dysprosium in luminescent materials doped with both lanthanides.

To determine the molecular weight distribution of natural polydisperse compounds (peat humic acids) and synthetic substituted polyvinyls, membrane filtration, gel-permeation chromatography, and spectrophotometric determination procedures were developed. The determination limit of polyvinyls was 0.1–0.2 mg/mL. The absorbance of polyvinyl solutions was a linear function of the concentration over the range 0.1–6.0 mg/mL. It was found that the size-fraction distributions of both humic substances and substituted polyvinyls depended not only on the molecular weight, but also the molecular conformation.

Chromatographic determination of 6-substituted 2-thiouracyls, thyreostatic preparations by M. S. Chernov’yants; A. O. Dolinkin; I. V. Braslavskaya (848-851).
Optimum conditions (borate buffer solution pH 9.18, voltage 20 kV) were selected for the separation and quantitative determination of antithyroid preparations, 6-R-2-thiouracyls, where R = H (TU), CH3 (MTU), n-C3H7 (PTU) by capillary zone electrophoresis in a quartz capillary 60 cm (effective length of 50 cm) × 75 μm. The procedure allows for the estimation of the concentration of substances in the ranges 1.3–103, 1.4–114, and 1.7–136 μg/mL, respectively, with detection limits of 0.93, 0.73, and 0.86 μg/mL for TU, MTU, and PTU, respectively. The procedure of the gas chromatographic-mass spectrometric determination of PTU with an analytical range of 10–50 μg/mL and a detection limit of 5.22 μg/mL is developed.

A computer program based on a mathematical simulation of gas chromatography was developed for the identification of components during the course of the chromatographic analysis of molecular mixtures. The source data for the program are natural parameters that characterize the stationary phase (certified characteristics) and easy-to-specify operational parameters of chromatograph units. An example of calculating the retention time of a component under specified conditions from a specified Kovats index or, vice versa, calculating the Kovats index from the elution time of a component peak is given.

A procedure is proposed for the generation of standard gas mixtures of volatile organic substances based on chromatomembrane gas extraction with the use of composite carbon-fluoroplastic matrices. The regularities of this process were found, and an adequate physicochemical model was developed. The advantages of the proposed procedure over traditional bubbling and chromatomembrane gas extraction on unmodified matrices were demonstrated.

The gas-chromatographic retention of pyridine, β-picoline, 3-pyridinecarbaldehyde, 3-pyridinenitrile, nicotinic acid, and nicotinamide on polar stationary phases was studied. A scheme was proposed and a procedure was developed for the determination of the reaction components of the catalytic oxidation of β-picoline to nicotinic acid on a column (3 m × 3 mm) packed with Chromosorb WAW + 10 wt % FFAP. The separation time was 28 min. The detection limits were 0.01 and 0.37 ppm for 3-pyridinenitrile and nicotinic acid, respectively.

Gas-chromatographic determination of alkylphenols in atmospheric air and the air of the working area by Yu. A. Karnauhov; N. V. Kuz’mina; F. F. Hizbullin; I. E. Alekhina; V. N. Maistrenko (867-870).
Sampling conditions are optimized in the determination of industrial alkylphenols (agidols) in atmospheric air and in the air of the working area using solid-phase preconcentration on Amberlite KhAD-7 and absorption by toluene. A procedure is developed for the gas-chromatographic determination of alkylphenols on their simultaneous presence in concentration ranges from 0.01 to 1 mg/m3 in atmospheric air and 0.1–50 mg/m3 in the air of the working area.

Conditions were selected for the separation of the herbicide glyphosate (N-(phosphonomethyl)glycine) and products of its microbiological utilization as N-acylated derivatives by ion-exchange liquid chromatography. The order of the elution of compounds on a Repro-Gel H column with UV detection correlates with their structures. The detection limits of the derivatives (wavelength 210 nm) are as follows (ng): glyphosate, 30; glycine and sarcosine, 20 and 43, respectively; aminomethylphosphonic acid, 45. The detection limit of methylphosphonic acid is 14 μg. Glyphosate and its biodegradation products were separated by thin-layer chromatography on plates with silica gel in the system isopropanol-5% aqueous ammonia solution (1: 1).

Procedures were developed for determining streptocide and norsulfazole in the Ingalipt aerosol; dexpanthenol and nipagin in the Dekspantenol aerosol; and oxymetazoline and benzalkonium chloride in a nasal spray by reversed-phase high-performance liquid chromatography (HPLC) in the gradient elution mode using the CH3CN-0.025 M aqueous solution mixture of KH2PO4 (pH 3.0) and UV detection. The developed procedures are comparable in accuracy and precision to chromatographic procedures recommended by regulatory documents; however, they ensure the simultaneous determination of all components of the pharmaceutical preparations and are more rapid and less laborious.

A rapid and sensitive high-performance liquid chromatographic (HPLC) assay for the simultaneous determination and quantification of cefpirome and cetirizine or cefpirome and levocetirizine in pharmaceutical formulations and human plasma without changing the chromatographic conditions is described. Chromatographic separations were performed on a prepacked Nucleosil 120, C18 (5 μm, 12.5 ± 0.46 mm) column using CH3CN: H2O (75: 25, v/v) as a mobile phase at a flow rate of 1 mL/min while UV detection was performed at 232 nm for monitoring the effluent. A number of other brands of C18 columns were also employed which had a significant effect on the separation. The method has been validated over the concentration range of 0.5–50 μg/mL (r 2 > 0.999). The limit of detection (LOD) and quantification (LOQ) for cefpirome and levocetirzine in pharmaceutical formulations and serum were in the range 0.24–1.31 μg/mL. Analytical recovery from human plasma was >98%, and the within and between-day relative standard deviation was <3.1%. The small sample volume and simplicity of preparation make this method suitable for use in pharmaceutical industries, drug research centers, clinical laboratories, and forensic medical centers.

Ion-selective sensors for determining Au(CN) 2 with membranes based on the ionic liquid tetradecylphosphonium dicyanoaurate by A. V. Kopytin; E. N. Pyatova; A. F. Zhukov; Yu. A. Politov; K. E. German; A. Yu. Tsivadze (888-890).
A polymeric membrane for an ion-selective electrode is proposed on the basis of supramolecular systems including a polymeric compound (polyvinyl chloride, PVC) and an ionophore (ionic liquid tetradecylphosphonium dicyanoaurate) in which ionic liquid is simultaneously used as a PVC plasticizer. The selectivity, linear response range, and potential stability of ion-selective electrodes with the optimum membrane composition are measured. The detection limit for Au(I) with the developed electrode is 4.5 × 10−7 M.

Particles of osmium or an inorganic polymeric film of osmium oxide-ruthenium cyanide (OsO-RuCN) electrodeposited on glassy carbon (GC) electrocatalyze the oxidation of dopamine (DA), adrenaline (AD), and noradrenaline (NAD). It is found that these biogenic amines are determined with a high sensitivity by oxidation at an electrode with an OsO-RuCN film. Procedures for the voltammetric determination of DA, AD, or NAD at a composite film electrode are developed. The currents of the substrate oxidation are linear functions of the concentrations in the ranges from 5 × 10−7 to 1 × 10−3 M for DA and from 1 × 10−6 to 1 × 10−3 M for AD and NAD.

An optical sensor has been proposed for the determination of silver by spectrophotometry. The sensor was prepared by immobilizing 5(p-dimethylaminobenzylidene)rhodanine on a transparent triacetylcellulose membrane. The effect of different variables on the response of the sensor was studied and the optimum conditions were established. The sensor responded linearly in the range 1.8–55.6 μM of silver with a limit of detection of 0.8 μM and a response time range of 8–10 min depending on the concentration of the silver ions. The presented optode is reversible and stable if stored in water for more than one month without reagent leaching. The relative standard deviation for seven replicated measurement of 4.6 and 37 μM silver was 3.15 and 2.76%, respectively. The sensor was successfully applied to the determination of silver in a silver sulphadiazine cream, an ore sample, and a radiology film.

Determination of fluoride ions by titration with aluminum chloride to a preset potential by V. V. Egorov; I. V. Kachanovich; V. A. Nazarov (902-906).
A procedure is proposed for determining fluoride ions based on titration with an aluminum chloride solution to a fixed potential. The procedure allows for the significant reduction of the determination error for fluoride ions due to the error of measuring the potential in comparison with direct potentiometry. The applicability of the procedure is confirmed by the results of determining fluoride ions in mixtures modeling the composition of Poles’e fluorinated cooking salt.

Determination of iodide and bromide by flow methods with amperometric detection by J. J. Mutic; S. D. Nikolic-Mandic; A. Dj. Lolic; D. D. Manojlovic (907-913).
Determination of bromide and iodide in real samples (water, pharmaceutical preparations, and biological material) was performed using modified flow injection analyses (FIA) with amperometric detection on platinum electrode. As an additional confirmation of FIA experiments, cyclic voltammetry was employed. Iodide was determined by the kinetic method, its limit of detection was 1.0 nM, and the linearity was 0.1–100 μM. The limit of detection for bromide determination was 50.0 nM and the calibration was linear for 2.5–100 μM and 0.1–10 mM. The relative standard deviation for 1 μM of iodide was 3.03% and, for 5 μM of bromide, it was 1.23% (n = 6). Both methods enable 60 analyses per hour to be performed.

ROSA analytical center for water quality control by N. K. Kutseva; A. V. Kartashova; A. V. Chamaev (914-919).
This paper describes the range of analytical problems to be solved, the equipment, structure, and personnel structure of the center, the methods for ensuring the quality of analyses, and the external relations.