Vol 71, No 7 (2016)

A simple, sensitive and selective solid phase microextraction with hollow fiber-supported multi-walled carbon nanotube functionalization reinforced sol–gel combined HPLC method was proposed for the determination of naproxen in tap, well and river water samples. In this method, functionalized multi-walled carbon nanotubes (MWCNTs) were prepared and held in pores of hollow fiber with sol–gel technology by immersion of polypropylene hollow fiber segment into the sol of the functionalized MWCNTs/silica composite and ultrasonically treated at room temperature. Effect of main parameters such as volume of donor phase, pH, extraction time, desorption time, type of desorption solvent, sample ionic strength and stirring rate were studied. Under optimum conditions, linearity was observed in the range of 0.03–500 ng/mL, with correlation coefficients of 0.997. The relative standard deviation for three replicate determinations of 50 ng/mL of naproxen was 4.3%. Limit of detection and pre-concentration factor were 0.008 ng/mL and 198, respectively. In order to check the applicability of the proposed method, it was used to determine trace levels of naproxen in different water samples.

A new terbium sensitized spectrofluorimetric method was developed for the determination of trace amounts of dopamine (DA) using ethylenediaminetetraacetic acid as co-ligand and cetyltrimethylammonium chloride as sensitizer. UV absorption and fluorescent spectra were used to investigate the photophysical properties of the ternary complex. Under the optimum conditions, the enhanced fluorescence intensities of the Tb(III) complexes increased linearly with the concentration of DA over the ranges 8 × 10^–8–5 × 10^–5 M and the limit of detection for DA was found to be 2.4 × 10^–8 M. The proposed method has been applied for the quantitative determination of DA in a pharmaceutical preparation and urine samples. The possible energy transfer mechanisms in the lanthanide complexes were discussed.

A possibility of using inductively-coupled plasma high-resolution mass spectrometry for the isotope analysis of monogermanes enriched with isotopes 72, 73, 74, and 76 has been studied. The effects of isobaric and polyatomic interferences in the spectrum of germanium isotopes have been discussed. It has been shown that the signal intensities of ⁱGeH⁺ ions formed in the inductively coupled plasma are 0.00001–0.0001 of the intensity of the ⁱGe⁺ signal. This can result in the overestimation of the found concentration of an isotope with a higher mass number next to the main isotope in recording spectra in the low and medium resolution mode. Approaches ensuring the determination of the isotope composition of highly-enriched monogermanes with the range of isotope concentrations extending five orders of magnitude have been proposed.

We obtained a gold nanomaterial/graphene oxide-modified glassy carbon electrode and characterized it using transmission electron microscope, scanning electron microscope, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy techniques. A response of the electrode using square wave anodic stripping voltammetry for Pb²⁺, Cu²⁺, and Hg²⁺ was found linear in the range from 1 × 10^–7 to 1 × 10^–11 M. The detection limits of Pb²⁺, Cu²⁺ and Hg²⁺ were 0.14, 0.5 and 1.2 pM, respectively. The method was applied to the simultaneous determination of Pb²⁺, Cu²⁺ and Hg²⁺ in seawater samples from a coastal region of Anatolia, and the results corresponded well with the values obtained by inductively coupled plasma-optical emission spectroscopy.

Using the IONCHROM software, we performed modeling of a new chromatographic system on an example of an ion chromatograph from METROHM. To determine all necessary parameters, we had to construct a dynamic map of this system, by which the conditions of the required separation were found in different pH and concentration ranges, after which three or four experiments with the chosen eluents were sufficient. The model corrected with the the found parameters was used to predict the behavior of the system and, in particular, to optimize the analysis.

A procedure is developed for the atomic emission analysis of human hair with the preliminary acid mineralization of samples and excitation of spectra in samples of dry residues of hair mineralizate on the end face of a carbon electrode in an alternating current arch. Spectra were recorded on an MFS-8 spectrograph modernized with a MAES photodiode array. Using the developed analytical procedure, samples of hair were analyzed for the presence of Al, B, Ca, Cu, Mg, Mn, Fe, P, Pb, and Zn. The average concentrations and concentration ranges of these elements were calculated for samples collected from 42 donors. The results obtained were compared with the published data for other geographical regions.

The identification of ignitable liquids is very important and challenging aspect in arson crime investigations. The detection of gasoline and diesel fuel components using solid phase micro-extraction prior to gas chromatography–mass spectrometry for the forensic analysis of fire debris has been carried out. Previous works show that the absorption characteristics of the substrate are one of the most important factors in determining the evaporation rate of the accelerants. In order to determine the presence of the fuel residues, four of the most common substrate materials were tested in this work; wool, cotton, silk and polyester. The obtained results indicate that both gasoline and diesel fuel accelerants persisted longer on wool and silk than on the other selected substrates. Such information illustrates the influence of fuel persistence times after extinguishing and the best materials to be scanned for ignitable liquids at the fire scene.

A procedure is developed for the determination of biologically active substances (BAS) of common St. John’s wort (Hypericum perforatum L.) by HPLC using two columns, Luna C18, 100 Å (for the determination of phenolcarboxylic acids and flavonoids), and Onyx Monolithic C18 (for the determination of phloroglucinols and naphthodianthrones), in the gradient elution mode with diode array detection. The detection limits for analytes are 0.05–0.20 μg/mL. To optimize the conditions, we studied the extraction of biologically active substances from St. John’s wort by a water–ethanol solution at different temperatures and pressures and under the effect of microwave radiation and ultrasound. The maximum amounts of substances were extracted in a dynamic mode under heat and pressure. The procedure was applied to the St. John’s wort samples of different brands and some pharmaceutical products based on it. The components of extracts were identified by retention times, UV spectra, and mass spectra. It was shown that the content of biologically active substances in pharmaceutical samples of St. John’s wort depends on the herb habitat. It was shown that hyperforin decomposed in pharmaceutical formulations based on St. John’s wort during storage.