Vol 71, No 6 (2016)

A simple, rapid, and efficient flotation-assisted dispersive liquid–liquid microextraction method was developed for preconcentration of trace amount of cobalt(II) ions. In this technique, a mixture of toluene and methanol (20: 80, v/v) was injected through the septum in the bottom of a narrow-bore tube containing cobalt solution. Afterwards, the fine droplets of extraction solvent were formed and cobalt (as 1-nitroso-2- naphtol complex) was collected on the surface of solution by aeration. The effect of different variables on the extraction efficiency of cobalt such as pH of solution, ligand concentration and injection volume was investigated using orthogonal array design. At optimum conditions, the calibration curve was linear over the range of 10–1000 μg/L. The detection limit, relative standard deviation and enrichment factor were 3 μg/L, 3.9% (n = 10) and 120, respectively. The developed method was successfully applied to the determination of cobalt in water and drug samples.

The value of the molar absorption coefficient of ozone in aqueous solutions (2992 ± 71 M^–1 cm^–1 at 260 nm) is found based on the determination of ozone concentration by iodometry. This value is confirmed by the results of determination of O₃ concentration by reaction with the bromide ion and virtually coincides with the maximum absorption coefficient of ozone in the gas phase in the region the Hartley band. In the determinations of ozone concentration in aqueous solutions by direct spectrophotometry, we recommend the value of the molar absorption coefficient ε(О₃)₂₆₀ = 3000 M^–1 cm^–1.

Problem of the determination of the composition of high-purity rare-earth metal salts is discussed. Prospects of the application of direct chemical methods to the determination of the water content of crystal hydrates of rare-earth metal salts used in the GET 173-2013 State Primary Standard of Mass Fraction and Mass (Molar) Concentration of Water in Solid and Liquid Substances and Materials are studied.

It was established that the micellar extracts of spices are electrochemically active on a glassy carbon electrode modified with cerium dioxide nanoparticles in a 0.02 M Brij® 35 in the presence of a phosphate buffer solution (pH 7.4) under the conditions of differential pulse voltammetry. The number of oxidation steps and their potentials vary over a wide range depending on the type of spice. A number of the oxidation peaks of the micellar extracts of spices were identified based on the oxidation potentials of the following individual antioxidants: gallic acid, ferulic acid, p-coumaric acid, caffeic acid, rosmarinic acid, thymol, eugenol, vanillin, syringaldehyde, capsaicin, rutin, quercetin, catechin, tannin, and curcumin. The contribution of the main antioxidants to the amperometric response of the extracts was confirmed by the standard addition method. A procedure for the voltammetric determination of the antioxidant capacity of the extracts of spices based on the oxidation of their antioxidants was developed. The antioxidant capacity of spices was evaluated from the total area of the oxidation steps in units of gallic acid, whose analytical range, detection limit, and determination limit were 50–2490, 11.9, and 39.6 μM, respectively. Twenty types of spices were analyzed. Positive correlations of the antioxidant capacity with the ferric reducing power and the antioxidant activity (r = 0.8971 and 0.9127, respectively at r_crit = 0.497) were found.

A flow-injection method is proposed for determining antiviral guanine derivatives, acyclovir, valacyclovir, ganciclovir, and famciclovir, based on their amperometric detection on a carbositall electrode with a preactivated surface. The method is characterized by a wide analytical range, relatively low detection limits (0.6–1.2 μg/mL), and high performance (75 h^–1). The results of examination of the accuracy and reproducibility of the analysis of solutions of different pharmaceutical forms containing the test substances are presented. The potentials of the developed flow-injection method in the implementation of the “Dissolution” test in an automated mode are demonstrated.

The objective of the present study was to develop and validate a rapid and simple stability indicating analytical method for estimating Ilaprazole. Ilaprazole was subjected to different stress conditions prescribed by International Conference on Harmonization (ICH) such as hydrolysis, oxidation, photolytic and dry heat degradation conditions. The drug was very susceptible to degradation under hydrolysis and photolytic conditions, less susceptible to oxidation and stable under dry heat degradation condition. An acceptable separation of drug and its degradants was achieved by using a C-18 column and mobile phase composed of ammonium acetate buffer (pH 3.2)—acetonitrile (55: 45, v/v). Flow rate was 1 mL/min and detection wavelength was set at 303 nm. Retention time of drug was found to be 6.6 min and analysis can be completed within 10 min. The method was validated with respect to linearity, precision, accuracy, robustness, LOD and LOQ as per ICH. The method was linear (R² = 0.996) in the range of 2.5–250 μg/mL. The recovery was in the range from 99.2–100.2%.

The present paper reports a comparison study of two data processing procedures in GC–MS metabolome components investigation based on two modern softwares: Automated Mass Spectral Deconvolution and Identification System (AMDIS) and GC–MS Solution Postrun Analysis (GC–MS SPA). GC–MS SPA is intended for manual integration and identification, while AMDIS is proposed as a fast, and automatic data analysis tool. Both methods are based on the same free-access library. In the present study, 12 compounds previously detected in a metabolomic fingerprint of grasshopper abdominal secretion, were tested at three concentration levels: 2.5, 5 and 10 μg/mL. The processing procedures were evaluated by comparison of peak area ratio for each tested concentration. The obtained results proved that processing with the use of AMDIS was more sensitive and enabled the identification of all compounds at the lowest selected concentration. Additionally, the differentiation of structurally similar compounds was possible with the use of AMDIS software.

A method is proposed for the gas-chromatographic determination of glycols as bis(diethoxyphosphoryl) alkanes formed by the Atherton–Todd reaction with diethyl phosphite. Gas-chromatographic and mass-spectrometric characteristics of the derivatives obtained are studied. Conditions of the phosphorylation reaction are optimized. The method is applied to the determination of the residual amounts of glycols in oligomeric glycol-o-phthalates.