Химия

Методом капиллярного электрофореза определено содержание
кофеина, консервантов (аскорбиновой, сорбиновой, бензойной
кислот) и подсластителей (сахарината натрия, ацесульфама ка-
лия) при совместном присутствии в 5 типах напитков: чае, кофе,
какао, газированных и энергетических напитках. Дана сравни-
тельная характеристика содержания кофеина и пищевых доба-
вок Е200, Е210, Е300, Е950, Е954 в указанных горячих и прохла-
дительных газированных напитках. Превышения нормативов по

By means of the Density Functional Theory DFT (B3LYP) method, quantum chemical computations of fundamental vibrations spectra of monosubstituted benzenes, pyridines, pyrones and thiopyrones have been carried out. The possibility of the aforesaid method application for the studied series of compounds vibrational spectra prediction have been substantiated.

The method of determination of tetracycline antibiotics (tetracycline, chlortetracycline, oxytetracycline, doxycycline) in the milk of methods HPLC-MS/MS/MS and HPLC-QTOF-MS, with a simple and rapid sample preparation. The ranges defined concentrations of tetracyclines in milk sample of 1 g was 1–200 ?g/kg. Relative standard deviation of the results of the analysis does not exceed 7%. The analysis duration 30–40 minutes.

A method for determining the 20 pesticides (azoxystrobin, boscalid, chlorpyrifos, cyprodinil, diazinon, dimethoate, fluazifop-P-butyl, malathion, metribuzin, penconazole, phosalone, pirimicarb, piri- miphos-methyl, prometryn, propargite, pyraclostrobin, pyrimethanil, triadimenol, triadimefon, trifloxystrobin) in grapes and tomatoes by high performance liquid chromatography with tandem quadrupole – time of flight mass spectrometry detector (HPLC-MS / TOF), using sample preparation QuEChERS.

It is shown that in the analysis of medicines fluoroquinolone by reversed-phase HPLC with fluorimetric detection modification mobile phase ?-cyclodextrin leads to a decrease in the detection limit of antibiotics to 8 times. The possibility of determination of cipro- floxacin in the presence of tetracycline and quinolone derivative series. The proposed method is tested in the analysis of pharmaceutical preparations containing ciprofloxacin.

Synthesis of eight phenylazonaphthols containing hydroxyl-, carboxy-, sulpho- and aldehyde groups was described. The data concerning elemental, thermogravimetric analysis, NMR-spectra and electronic absorption spectra in ethanol were described. 

Предпринято квантовохимическое обоснование природы ин- термедиата (тиильный радикал) и региоселективности (S,S- сочетание) реакции гомолитической окислительной димериза- ции L-цистеина с образованием L-цистина. Протеканию реакции не препятствует электростатический фактор.

A quantum chemical substantiation of the intermediate (thiyl radical) nature and reaction regioselectivity (S,S-coupling) of the L-cysteine homolytic oxidative dimerization resulting by the L-cystine formation has been carried out. The electrostatic factor does not prevent the reaction occurrence.

Development of methods for identification of oils is of high priority in oil industry. The following parameters for 2963 oil samples from five oilfields in the Samara region were determined: density, fraction yield at 200 °C and 300 °C, the mass fraction of sulfur, hydrogen sulphide, methyl and ethyl mercaptan, the mass concentration of chloride salts, the saturated vapor pressure. The matrix of experi- mental data was analyzed using principal component analysis (PCA) and factorial discriminant analysis (FDA) methods.

The influence of the nature of a modifying additive selected from the class of stabilizers and thickeners (high-molecular-weight chitosan, starch, xanthan gum, sorbitol, and pyridoxine hydrochloride) on the rheological properties of the concentrated chitosan–organic acid– water system (freshly prepared or stored at 4 and 20°C) was studied. It is shown that all the modifiers have a stabilizing and thickening effect, resulting in an increased viscosity of the multicomponent system and a lower rate of its fall in time.