Vol 72, No 5 (2017)

The publications dedicated to the determination of individual sulfur-containing compounds in liquid hydrocarbon raw materials and their processing products by gas chromatography are summarized. In the analysis of petroleum raw materials, the preliminary separation of sulfur-containing compounds and a hydrocarbon matrix is usually performed. In the analysis of liquid oil refining products and gas condensate, the direct determination of individual sulfur-containing compounds can be frequently conducted. The use of currently available sulfur-selective chemiluminescence and atomic emission detectors in combination with nonpolar or slightly polar capillary columns and also two-dimensional chromatography is the most promising.

Uncontrolled partial losses at the step of sample injection into a gas chromatographic column increase errors of determination by the external standard, absolute calibration, and standard addition methods. Modified method is proposed for quantitative analysis; it includes the introduction of additional standards into test samples and calculations by the ratio between the areas of chromatographic peaks and peaks of standards rather than the absolute areas of chromatographic peaks. The calculation equations are presented for modified methods of quantitative analysis using additional standards, including those for estimating random errors of determination. The relative standard deviations of peak areas were shown to be 6–38-fold lower than the analogous statistical characteristics of absolute areas. This ensures a high accuracy of quantitative determinations even under the conditions of low reproducibility of sample dosing. Solvents contained in the analyzed samples can be used as additional standards. This version can be recommended as a routine method of data representation and processing.

A methodology for separation, characterization, and quantitative elemental analysis of volcanic ash nanoparticles is proposed. A combination of field-flow fractionation in a rotating coiled column and membrane filtration is used in the isolation and separation of nanoparticles. The size and morphology of nanoparticles were studied by static light scattering and scanning electron microscopy. The concentration of major- and trace elements in the bulk sample and the separated fractions was determined by inductively coupled plasma atomic emission spectrometry and mass spectrometry. It is shown that the total concentrations of most elements in the ash sample are comparable to their average concentrations in the Earth’s crust. On the other side, in the fraction 50–100 nm, the concentrations of Ni, Zn, Ag, Sn, Sb, Pt, Tl, Pb, and Bi are one or two orders of magnitude higher than their total concentrations, which probably indicates the preconcentration of corresponding elements from volcanic gases by nanoparticles. In the fraction represented by water-soluble forms of elements and nanoparticles smaller than 50 nm, Cu, Zn, Pb, and several other elements are found; the partition of elements between the solution and solid phase (nanoparticles) is assessed. The proposed methodology requires further development and application to the analysis of volcanic ash from various regions of the Globe.

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil.

Di(2-ethylhexyl) phthalate (DEHP) is used as plasticizer in polyvinylchloride (PVC) plastics. Its metabolites and the parent phthalates are considered toxic. As the DEHP plasticizers are not chemically bound to PVC, they can migrate, evaporate or be leached into indoor air and atmosphere, foodstuff, and other materials. We have reported a novel, easy and available analytical method for the determination of DEHP and its metabolite, mono(2-ethylhexyl) phthalate (MEHP) in human urine samples by the in-syringe dispersive liquid–liquid microextraction method coupled with gas chromatography with flame ionization detector. The limits of detection and precision (RSD) were 2.5 μg/L and 1.4% for DEHP and 1.1 μg/L and 3.0% for MEHP, respectively. This method could be utilized for routine monitoring of the trace DEHP and MEHP in urine of human exposure to plasticizers.

Sunitinib malate, as an anticancer compound and a multi-targeted tyrosine-kinase inhibitor for treatment of glioma, was comprehensively studied by using different liquid chromatography methods. Since sunitinib malate shows Z-E isomerism, various reverse phase high performance liquid chromatography (RP-HPLC) programs were designed to access quantitative determination and good separation of Z-E stereoisomers. Moreover, some impurities including N-oxide and impurity B were to be separated from the main isomer with acceptable resolution. In the present work, different RP-HPLC programs were developed in which the type of mobile phase, flow rate, pH, and temperature were optimized to reach the best analysis conditions and control the rate of Z to E conversion. In addition, the effect of some operational parameters during the solution preparation including initial concentration of the analyte, temperature, pH, and type of solvent on the stability of Z isomer were investigated. The opted conditions for quantitative analysis were C8-Hector column as stationary phase, methanol as solvent, ammonium acetate buffer containing triethylamine as mobile phase, the pH of mobile phase of 8.5, the flow rate of 1.0 mL/min, and detection at 425 nm. In this situation the peaks of E and Z isomers were at 16.3 and 19.7 min. Full validation of the designed method was done based on ICH guidelines.