Vol 73, No 2 (2018)

A review of methods for the preparation of standard gas mixtures (SGMs) with the known concentrations of organic and inorganic gases and vapors is presented. The classification of methods is proposed and their advantages and disadvantages are compared. Along with the widely known thermal diffusion and gasextraction methods and devices for the preparation of SGMs functioning on their basis, i.e., sources of gas and vapor microflows and vapor-phase sources of gas mixtures, the review considers and discusses metrological possibilities proposed by Russian researchers of chromatomembrane and chromato-desorption methods of SGM preparation and corresponding instrumentation.

Trace amounts of titanium(IV) were determined with a simple and selective method based on cloud point extraction. Preconcentration of titanium from aqueous solution was performed using Triton X-114 surfactant and 4-(2-pyridylazo) resorcinol as complexing agent. After centrifugation, the surfactant- rich phase was removed, diluted with water and ethanol, transferred into a 500 μL quartz cell, and its absorbance was measured at 520 nm. The effect of experimental conditions influencing the extraction process was considered. In the optimum conditions, linearity ranges was 0.01–0.1 with the correlation coefficients (R²) of 0.9903. The limits of detection was 0.005. The method was successfully used for the determination of titanium(IV) in the samples of ore and river water with relative recovery of 98‒99%.

A micelle-mediated separation/preconcentration technique was used for the determination of trace Cd(II) in solid and liquid samples by flame atomic absorption spectrometry. Cadmium ions reacted with ammonium pyrrolidine dithiocarbamate to form a chelate that was extracted from aqueous medium by a non-ionic surfactant Tergitol NP-7 at pH 7. Values of pH, concentrations of ammonium pyrrolidine dithiocarbamate and Tergitol NP-7, temperature, incubation time, sample volume and matrix ions were optimized. The enrichment factor of the method was found to be 25, and the detection and quantitation limits were 1.5 and 3.8 μg/L, respectively. Assessment of the method was performed with a certified reference material, and the observed concentration of Cd(II) was in good agreement with the certified value. The method was also applied to the determination of Cd(II) in waters and industrial samples. Cd(II) concentrations in two industrial ZnO composite samples were determined between 59 and 69 μg/g.

A new chiral sorbent based on mercaptosilica modified by gold nanoparticles, then treated by 3-mercaptopropionic acid and macrocyclic antibiotic vancomycin, was obtained. The enantioseparation of isomeric β-blockers (nadolol, atenolol, metoprolol, alprenolol, oxprenolol, and pindolol) by HPLC was studied on the synthesized sorbent. The effect of the composition of the mobile phase (nature and concentration of the organic solvent, concentration and pH of the buffer solution) on retention times of β-blocker enantiomers, selectivity of separation, and resolution of chromatographic peaks were studied. The best separation was achieved for pindolol and metoprolol. The procedure was used to determine the pindolol enantiomers in the preparation “Visken,” and metoprolol in the “Vazocardin” preparation.

Herbs and herbal based products have been widely used, but some products might contain no herbal ingredient as claimed in the product label. Therefore, it is crucial to develop a fast, sensitive and reliable method to analyze the herbs and their finished products. The roots of Eurycoma longifolia, and the health supplement of E. longifolia and Cordyceps were used as the sample matrices in this study. Sonication assisted extraction was applied to extract the marker compounds, namely eurycomanone and cordycepin from E. longifolia and Cordyceps, respectively. The presence of the marker compounds was established by high throughput ultra-performance liquid chromatography tandem mass spectrometry (UPLC‒MS/MS) using a highly sensitive and selective technique of multiple reaction monitoring (MRM). The positive ion transitions in MRM for eurycomanone and cordycepin are m/z 409 → 391 and m/z 252 → 136, respectively. The test method was validated for its robustness, accuracy, precision, linearity, detection and quantitation limits, as well as estimated for its measurement uncertainty.

The electrochemical oxidation of nortriptyline at a carbon ionic liquid electrode (CILE) was investigated. Nortriptyline is electrochemically inactive on conventional electrodes but CILE exhibited excellent electrocatalytic activity toward oxidation of nortriptyline with the well-defined anodic peak at 860 mV. This characteristic was attributed to the outstanding conductivity and electrocatalytic effect of the ionic liquid, 1-octylpyridinum hexaflourophosphate, used as a binder in the construction of the electrode. The influence of experimental parameters such as pH and sweep rate was also studied. The quantitative determination of nortriptyline was performed using differential pulse voltammetry technique. Under selected conditions the anodic peak current was linear to nortriptyline concentration in the ranges of 4.8 × 10^–6 to 2.4 × 10^–5 M and 2.4 × 10^–5 to 6.4 × 10^–5 M, with correlation coefficients of 0.9992 and 09949, respectively. The detection limit was 3 × 10^–7 M.

We examined 144 samples of red dry wines of varieties Cabernet and Merlot, produced in the territory of the main wine-making enterprises of the geographical zones of Krasnodar krai, to consider the possibility of determining the regional and varietal identity of red wines. The concentration of micro- and macroelements in the wines was determined by inductively coupled plasma atomic emission spectrometry. Chemometric studies were performed in the Statistica package environment, using discriminant analysis and classification trees. Adequate mathematical models were proposed for wines to identify the grape variety and the region where it grows. A software product was developed that automates the necessary calculations.