Journal of Analytical Chemistry

The results of the elemental analysis of blood serum are often used for the diagnosis of different diseases associated with derangements of mineral metabolism. In this work, we studied the main sources of a systematic error in the atomic-emission spectrometric (AES) analysis of blood serum and developed a procedure for the AES determination of Ca, Cu, Fe, Mg, P, and Zn in the human blood serum. The repeatability relative standard deviations of determinations varied from 10 to 24%.

A rapid, relatively sensitive and simple kinetic-spectrophotometric method for determining sodium salicylate content has been developed and validated. This method was based on the Fenton reaction that involved mixing of ferrous ions, hydrogen peroxide and sodium salicylate in acetic buffer medium. Ferrous ions, oxidized by hydrogen peroxide, formed with salicylate anion purple complex whose degradation started immediately. This effect was monitored by the decrease of absorbance at 525 nm. The experimental results showed that the most favorable conditions for complex degradation are: pH = 3.9, $$ c_{Fe^{2 + } } $$ = 4.7 × 10−5 M, and $$ c_{Fe^{2 + } } /c_{H_2 O_2 } $$ = 1/150. The activation energy (E a) calculated from the slope ( $$ - \frac{{E_a }} {{2.303R}} $$ = 2.84 × 103) was 54.3 ± 0.6 kJ/mol. The absorbance increased linearly with the increment of sodium salicylate concentration (r = 0.9983). The system obeyed Beer’s law in a range of 0.93–9.3 μg/mL of sodium salicylate concentration. The calculated values for the detection limit, according to two formulas, available in the literature, were found to be 0.67 and 0.48 μg/mL. The variables affecting the rate of the proposed reaction were investigated. The relative standard deviations for five-replicate determinations of 0.93, 3.31, and 9.30 μg/mL of sodium salicylate were calculated to be 6.80, 2.95, and 1.71%, respectively. The proposed method has been successfully applied to determining sodium salicylate in human serum and wine and validated by HPLC (high-pressure liquid chromatography) reference method.

The problem of determining biologically active low-molecular-weight aminothiols, such as cysteine and glutathione, requires the development of new methods and analytical reagents. Among the latter substances, a group of spiropyrans can be distinguished, which are photochromic organic substances reaching an equilibrium between their cyclic and open forms in solutions. We consider a possibility of using benzofuran spiropyrans as analytical reagents for aminothiols and studied the effect of various substituents in their structure on the change in optical properties in the presence of cysteine and glutathione. An equilibrium in solutions of benzofuran spiropyrans bearing a hydroxyl group in position 7 shifts in the presence of analytes towards the formation of a colored open form. The considered spiropyrans were used to create a simple, selective, and sensitive procedure for the spectrophotometric and kinetic determination of cysteine and glutathione in vitro.

The determination of Pb and Cd by electrothermal atomic absorption spectroscopy with the slurry sampling of carbonized samples into a graphite furnace was considered. Textural and chemical properties of new palladium-carbon modifiers based on activated carbon and carbonized nutshell were studied by high-resolution electron microscopy, x-ray photoelectron spectroscopy, and the adsorption of liquid nitrogen. Advantages of activated carbon as a modifier support were substantiated. Pyrolysis and atomization temperatures were selected for determining elements using matrix modifiers. The developed analytical procedure was tested with reference samples of plant materials. The results obtained agreed well with the certified analyte concentrations. The RSD values were no higher than 8% for lead and cadmium in the ranges 0.3–3.3 and 0.110–1.34 mg/kg, respectively.

The electrophoretic behavior of polyhexamethyleneguanidine hydrochloride (PHMG HC), hexamethylenediamine (HMDA), and guanidine hydrochloride (GHC) was studied. It was shown that PHMG HC and the initial toxic components of its synthesis, GMDA and GHC, can be separated. A procedure was developed for determining PHMG HC oligomers, GMDA, and GHC in aqueous solutions in concentrations from 0.007 to 0.05 mg/mL by capillary electrophoresis. The procedure was applied to the analysis of model mixtures of these compounds.

3-(4'-Amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid, was synthesized and used to construct a modified-graphene oxide nano sheets paste electrode. The electro-oxidation of isoproterenol at the surface of the modified electrode was studied using cyclic voltammetry, chronoamperometry, and square wave voltammetry. Under the optimized conditions, the square wave voltammetric peak currents of isoproterenol increased linearly with isoproterenol concentrations in the range of 2.5 × 10–8 to 2.0 × 10–5 M and detection limit of 12 nM was obtained for isoproterenol. Finally this modified electrode was used for determination of isoproterenol in some real samples.

The conditions of the sorption concentration of o-xylene and polynuclear aromatic hydrocarbons (PAHs) on hypercrosslinked polystyrene in the dynamic mode are developed. A procedure is proposed for the determination of o-xylene and PAHs in thawed snow, based on the sorption preconcentration of these compounds and their further determination by gas chromatography–mass spectrometry. Samples of thawed snow taken in the park of Moscow State University are analyzed.