Reagentless system for sulphite determination based on polyaniline

A new reagentless system for sulphite (or sulphur dioxide) determination is reported based on the use of an organic conducting polymer, polyaniline, and its absorbance variation at 550 nm, depending on the sulphite concentration. After chemical polymerisation of aniline a very thin film of polyaniline is obtained. Although the response is not fully reversible, each film can be used for at least 10 measurements for low analyte concentrations (up to 0.5 mg l⁻¹) and five measurements for higher sulphite concentrations. Moreover, the reproducibility, ease of preparation and low cost of the films, permit the use of a new disposable system for each measurement. When the change in absorbance at 550 nm was measured for 210 s (stabilisation time), the system showed a linear response, which ranged from 0.025 to 1.50 mg l⁻¹ of sulphite. A theory with regard to the reaction mechanism between the polyaniline films and sulphite is also proposed. The system was applied to sulphite determination in wine samples and the results were in agreement with those obtained by the Official Method of Analysis (iodometric titration).     

一种测定蛋白质的分子吸收光谱分析新体系

使用四溴荧光素(TBFS)作为蛋白质的染色剂,建立了一种测定蛋白质的分子吸收光谱分析新体系———BSA 四溴荧光素,体系十分简单,BSA浓度在0.11～60.0μg·ml-1范围符合比耳定律;测定15.0μg·ml-1BSA溶液10次,求得相对标准偏差为1.26%,桑德尔灵敏度为0 094μg·cm-2。可直接用于血清样品中蛋白质的测定,测得质量控制血清样品中蛋白质质量为35.4±2.4mg,与标准值36.9mg吻合。回收率在97.0%～108.3%之间,结果满意。     

Concentrated electrolyte solutions at high temperatures and pressures

A survey is given of recent experimental results obtained from high-temperature, high-pressure investigations with water, aqueous solutions, and ionic fluids. Data on the static dielectric constant of water to 550°C and 5 kbar are given and discussed with respect to their relation to water structure. Infrared and Raman spectra of HDO in pure water have been obtained to 400°C and 4 kbar, which give information on hydrogen bonding. Xe–H₂O and CO₂–H₂O mixtures were investigated in the infrared. Ni(II) and Cu(II) complexes were investigated by absorption spectroscopy in aqueous solutions of high chloride content to 350°C and 2–6 kbar. The gas-liquid critical point of ammonium chloride was found at 880°C and 1635 bars. This fluid appears to be predominantly ionic even in the critical region. The possibility of converting pure polar fluids such as ammonia and water into concentrated ionic solutions by self-ionization at very high pressures is mentioned.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.     

Tandem cleavage of 2,3,5-trimethyl 7-trifluoroacetyl-1,2,3,4-tetrahydro-pyrrolo[1,2-<Emphasis Type="Italic">c</Emphasis>]pyrimidine by activated alkynes,caused by Michael addition of a tertiary nitrogen atom to a triple bond

The interaction of 7-trifluoroacetyltetrahydropyrrolo[1,2-c]pyrimidine with acetylenedicarboxylic ester (DMAD) and ethyl propiolate in acetonitrile and alcohols has been studied. It was established that DMAD splits pyrrolopyrimidine at the aminal fragment in acetonitrile and methanol with the formation of 1-H-and 2-(N-dimethoxycarbonylvinyl-N-methyl)aminoethyl-1-methoxymethyl-3-methyl-5-trifluoroacetylpyrroles. In acetonitrile ethyl propiolate splits pyrrolopyrimidine both at the aminal fragment and at the C₍₃₎-N₍₂₎ bond (Hofmann reaction), but in ethanol only at the C₍₃₎-N₍₂₎ bond with the formation of 2-propenylpyrroles. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1082–1087, July, 2007.     

煤中有机硫形态结构和热解过程硫变迁特性的研究

利用热解 质谱并结合固定床热解反应装置，对煤中有机硫的形态主其对加氢热解过程 变迁特性的影响，进行了较系统的研究。结果表明，煤中有机硫的形态结构在褐煤中主要以脂肪族、芳香族硫化物为主，而在 煤中则主要以各种不同芳构化程度的噻吩结构为主，初步表明煤中有机硫形态结构随煤变质程度的变迁呈较强的连续递变性。煤热解过程中硫在呼产物中的变迁和分布与煤中有机硫的形态结构特点密切相关。较高芳构化噻吩结构不完全的氧     

LC–MS Determination and Pharmacokinetic Study of a Novel Sulfonylurea: Potential Hypoglycemic Agent in Rat Plasma

To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea (G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte was analyzed on a Kromasil C₁₈ column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow rate was 0.2 mL min⁻¹. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was linear over the concentration range of 2.0–500.0 ng mL⁻¹. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV). This validated method was successfully applied to the pharmacokinetics of G004 in rats.     

Salt promoted adsorption chromatography of malted barley amylases

Summary A sequence for the fractionation of the amylasic components from a malted barley extract is proposed using two salt-promoted, adsorption processes: thiophilic interaction chromatography (TIC) and hydrophobic interaction chromatography (HIC).Two fractions containing -amylase activity were recovered during the thiophilic chromatography; the first was resolved in to -amylase I and -amylase I by HIC on a phenyl-sepharose column; an enrichment factor of 32 was achieved for -amylase I. The other amylasic component eluted from the thiophilic gel was characterized as -amylase II. Although the adsorption of malt amylases on phenylsepharose and the thiophilic adsorbent is salt promoted, the interactions involved in each case are clearly distinguished by the different behaviour and disparate salt effects.     

Determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process

Polymer enhanced ultrafiltration (PEUF) is a newly developed method for the removal of heavy metals from aqueous solutions. This method was applied for the removal of mercury and cadmium with the presence of polyethyleneimine (PEI) as a water soluble polymer. After ultrafiltration experiments for metal–polymer mixtures, two separate streams, namely, retentate and permeate, former of which contains mainly metal–polymer complex and free polymer molecules while latter of which mainly contains free metal ions, were obtained. At the end of PEUF experiments, performance of operation was determined by concentration analyses which was achieved by atomic absorption spectroscopy (AAS) applied in a different way for permeate and retentate streams considering the effect of presence of polymer. For mercury analysis, cold vapor AAS was applied. It was observed that the presence of PEI did not affect the atomic absorption signal when 10% HCl was added to the sample solutions. For calcium and cadmium, flame AAS was used. It was observed that change in PEI concentration results in change in measured concentration of calcium and cadmium. Therefore, two new approaches were developed for accurate measurement of concentrations of calcium and cadmium. It was also observed that presence of other metals did not affect the accuracy of the measurement of a particular metal in the concentration range studied.     

HPLC determination of pyroglutamic acid as a degradation product in parenteral amino acid formulations

Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects.Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur.The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 m Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5.Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce.