Vol 74, No 8 (2019)

One of the main limitations of capillary electrophoresis (CE) is the sorption of basic compounds on the walls of a quartz capillary. To prevent this phenomenon in CE, supporting electrolytes with various additives that prevent the sorption of analytes due to the formation of dynamic coatings are commonly used. Alternatively, covalent coatings, which have a number of advantages and expand the analytical capabilities of CE, are used. The main methods of the formation of coatings covalently bound to the walls of a quartz capillary are considered.

Silica modified with 2-nitroso-1-naphthol-4-sulfonic acid (NNS), quantitatively extracting palladium(II) from solutions in the pH range 1–8, is proposed for the preconcentration and photometric determination of palladium(II) in the adsorbent phase. In the sorption of palladium(II) from solutions with pH 1–3, complex compounds of the stoichiometry Pd : NNS = 1 : 2 were formed on the adsorbent surface. They has intense lilac color and a maximum in diffuse reflectance spectrum at 550 nm. A procedure is developed for sorption–photometric determination of palladium in the version of diffuse reflectance spectroscopy with a limit of detection 0.03 µg per 0.1 g of the sorbent. The analytical range is 0.1–10 µg/0.1 g. The procedure was tested in the determination of palladium in wastewater and water extract from the soil.

Myrtus communis L. essential oils were extracted by simultaneous distillation extraction method and studied with gas chromatography–mass spectrometry (GC–MS). The obtained mass spectra were investigated by searching in NIST library, and 54 components were identified, but due to several problems such as varying baseline due to column bleed, low signal-to-noise ratio of peaks, and co-elution, some of components did not have satisfactory match factors. Chemometric resolution techniques were used to resolve these problems. The number of identified components was expanded to 67 using combination of GC–MS with resolution technique. In addition, the presence of worthful components such as α-Pinene (36.19%), 1,8-Cineole (11.44%), d-Limonene (10.04%), Linalool (7.76%), α-Terpineol (5.51%), linalyl acetate (4.19%) and α-Terpineol acetate (2.61%) in Myrtle essential oils have been verified. The results of this study indicate that joining of hyphenated chromatographic methods and multivariate curve resolution techniques can be useful for comprehensive, rapid, and accurate analysis of complex natural product such as Iranian Myrtle essential oils.

A procedure is proposed for the determination of priority polycyclic aromatic hydrocarbons (PAH) in water by gas chromatography–tandem mass spectrometry. The procedure differs from the known ones by the low level of the limit of determination, 0.1–1.0 ng/L and intra laboratory precision of 15–20%. A simple and rapid sample preparation procedure—a single extraction of PAH with n-hexane (sample volume 0.1 L, concentration factor 10²–10³)—can be easily implemented in routine analyses in monitoring research. The direct analysis of extracts eliminates the risk of losses of easily volatile PAH. Among the additional advantages of the procedure are small volumes of the extractant (1 mL) and the organic solvent, respectively, for its subsequent utilization. The procedure was tested in monitoring PAH in waters of Lake Baikal and its side streams and in the analysis of atmospheric precipitates on urban and background areas.

A method for determining aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments using gas chromatography–mass spectrometry and HPLC with spectrofluorimetric detection, respectively, was developed. Various methods are studied for extracting PAHs from the matrix of a solid sample: extraction with organic solvents under mechanical stirring, ultrasonic treatment, and in a Soxhlet apparatus. The recovery depends on the method of sample treatment; it is maximum at mechanical stirring and extraction in the Soxhlet apparatus (up to 60–80%). The simplest method including mechanical stirring is optimal. A procedure for the quantitative separation of aliphatic hydrocarbons and PAHs in a wide concentration range is proposed using column chromatography on silica gel. The limits of detection for PAHs were 0.1–3 ng dry weight; RSD = 4% for benzo[a]pyrene at a concentration of 1 ng/g dry weight. The developed procedure was used to determine aliphatic hydrocarbons and PAHs in real samples of bottom sediments. The proposed option of sample preparation enables identifying and quantifying two groups of substances of petroleum components from one sample and thereby expands the possibilities of determining the source of hydrocarbon contamination of a water body.

Present work deals with a new ion selective membrane electrode suitable for determining trace cadmium(II) concentration in environmental samples. After structural and morphological characterization, the synthesized nanocomposite was observed to be selective towards Cd(II) on the basis of distribution studies, and was further employed in fabricating Cd(II) ion selective membrane electrode. Polyaniline incorporated zirconium phosphoborate nanocomposite prepared by the sol-gel method was used as an electroactive material and the epoxy resin, araldite as binder in the fabrication of membrane electrode. The fabricated electrode exhibits sub-Nernstian response of 22.9 mV/decade over a wide concentration range, low limit of detection (4 × 10^–7 M), fast response time (14 s), long life time of 4 months and wide pH working range (2.5 to 8.0). The electrode was successfully used for estimation of trace levels of Cd(II) in industrial effluents of Ni‒Cd battery and printer toner units.

Methods for the voltammetric determination of flavonoids (rutin and quercetin) using electrodes modified with CeO2 nanoparticles and various surfactants have been developed . The voltammetric characteristics of analytes are most properly recorded on a glassy carbon electrode modified with CeO₂ nanoparticles dispersed in anionic sodium dodecyl sulfate. The electro-oxidation of quercetin and rutin is adsorption-controlled and proceeds with the participation of two electrons and two protons. Under conditions of differential pulse voltammetry in a Britton–Robinson buffer solution with pH 2.0, the analytical ranges are 0.01–1.0 and 1.0–250 µM for quercetin and 0.10–100 µM for rutin with the limits of detection (S/N = 3) of 2.9 and 28 nM, respectively. The proposed approaches were tested in analyzing water and alcohol extracts from medicinal plant materials (St. John’s wort herb, marigold flowers, and bearberry leaves). The conditions for the extraction of flavonoids from raw materials with ethanol are found. The results of the voltammetric determination of quercetin and rutin in plant raw materials correlate with the total flavonoids according to spectrophotometry: r = 0.929 with r_crit = 0.521 for n = 11 in the case of quercetin and r = 0.951 at r_crit = 0.729 for n = 6 for rutin.

A method is considered for determining concentrations of components in solutions of two electrolytes with one common ion. We used optical micrometry by measuring the degree of swelling of granules of crosslinked polyvinyl alcohol in a test solution. To determine the concentration, the test solution was successively diluted, and a set of polymer swelling values was obtained. The data were used to build a total calibration curve for this mixture. Concentrations of the components of the solution were found by the least squares method, the software implementation of which is based on the coordinate descent.