Simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals in organometallic compounds

A method for the simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals which combines features of the known intermediate storage technique in organic microanalysis and formation of the metal-oxine complex, is described. Carbon and hydrogen are determined gravimetrically as usual. Sulfur and halogens are absorbed and stored on electrolytic silver. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulfur as sulfur dioxide and halogens as hydrogen halides and regenerates the silver layer. The liberated gases can be easily absorbed by dilute hydrogen peroxide and determined titrimetrically. The metal oxide, remaining in the platinum boat, is dissolved in a mixture of nitric-perchloric acids in a test tube and the metal content is determined gravimetrically and titrimetrically using 8-hydroxyquinoline.     

A fast, sensitive HPLC method for the determination of esterase activity on alpha-tocopheryl acetate

Although data on the behavior of tocopheryl acetate (Tac) in the gut is rare, some studies show that this ester is hydrolyzed in the intestine and the released tocopherol (Tol) is absorbed. An HPLC method is published for the simultaneous analysis of Tol and Tac in mixed micelles. This study shows how this method is used for the measurement of esterase activity on Tac using commercial cholesterol esterase. The rate of hydrolysis is determined in less than 20 min on the basis of both Tac disappearance and Tol appearance. The present method is useful for investigating esterase activities on Tac in model systems that mimick the absorption environment or in any biological or nonbiological medium.     

Evolution of oxide layer on a cobalt foil studied by temperature programmed, reduction

Cycles of alternate TPRed and TPOx or isothermal oxidation result in step-by-step oxidation of Co-foil. The amounts of reversibly and irrreversiblty absorbed oxygen were determined. Multiplication of the Red-Ox cycles established the amounts of reversibly absorbed oxygen, so that a limited thickness of the reducible oxide layer should be assumed.     

Mikrobestimmung von Kohlenstoff und Wasserstoff,sowie von 14C,Tritium und Deuterium im Stickstoffstrom

A microanalytical method for the determination of carbon and hydrogen is described. The procedure involves the combustion of the organic substance in a stream of nitrogen and the oxidation of the decomposition products with oxygen. Halogens and sulphur are absorbed by the combustion catalyst (according to Körbl), whereas nitrogen oxides are reduced on a copper surface. The combustion products, CO₂ and H₂O are determined gravimetrically; in the case of radioactive samples they are appropriately absorbed and counted in a liquid scintillation counter. Strongly quenching singly and doubly labelled samples, which cannot be accurately counted even by modification of the counting device, give equally high radioactive yields (75% for ¹⁴C, 30% for ³H), since counting is not influenced by other gaseous impurities. Deuterium is quantitatively determined by measuring the intensity of the OD-signal at 2500 cm^?1 with an infrared spectrometer.     

The fluorimetric determination of phosphate with thiamine

A method for the microdetermination of sulphur in organic compounds by means of combustion in a flow of oxygen is described. The oxides of sulphur are absorbed and stored on a small silver layer. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulphur as sulphur dioxide and regenerates the silver layer. The sulphur dioxide can be easily absorbed by dilute hydrogen peroxide and determined by any convenient method.     

Estimation of gas transport coefficients from differential permeation, integral permeation, and sorption rate data

Experimental methods for studying the transport of gases in polymers may be divided into three categories: integral permeation rate measurement, in which the cumulative amount of a penetrant that has passed through a membrane is determined; differential permeation rate measurement, in which the rate of penetration through a membrane is measured directly; and sorption rate measurement, or determination of the cumulative amount of a penetrant absorbed in a polymer sample. This paper reviews commonly used techniques for estimating diffusion coefficients from transport data of all three types. Several new estimation formulas are presented, and the relative merits of different measurement and estimation methods are discussed. A general relationship between the traditional time lag method for integral rate data analysis and a recently developed moment method for differential rate data analysis is established, extending the applicability of the moment approach to the analysis of non-ideal transport in membranes of arbitrary geometry and composition.     

Notes on analytical procedures : Determination of carbon dioxide

For the determination of carbon dioxide, methods suitable for general applications are described. a. Macro-titration method. The CO2 is absorbed in sodium hydroxide in a bubble column filled with glass beads. The excess of NaOH is titrated after the addition of BaCI2. b. Scmi-micro-titration method. The CO2 is absorbed in barium hydroxide, the excess of which is determined by titration with 0.1 n hydrochloric acid on cresolphthalein as the indicator. The absorption and titration are performed in a special vessel in which the liquid is kept in circulation by the injected stream of air. c. Gravimetrical method.Method b. is specially recommended.     

应用壳核纳米微球固定乙醇脱氢酶联用 HPLC对抑制剂筛选

对新型聚甲基丙烯酸甲酯/壳聚糖纳米微球进行制备、纯化和表征,采用该纳米微球对乙醇脱氢酶进行固定化。让多组分天然产物直接作用于固定化乙醇脱氢酶,通过高效液相色谱(HPLC)检测固定化酶吸附组分,研究多组分天然产物混合物对乙醇脱氢酶具有抑制活性的有效成分。结果表明:由HPLC检测到的被固定化乙醇脱氢酶从多组分化合物中直接吸附的组分对乙醇脱氢酶均有较强的抑制作用,说明该方法从多组分直接筛选抑制剂是可行的,同时,本文所检测到的7种天然化合物对乙醇脱氢酶的抑制活性还没有报道。     

大气环境中硫化氢的测定——亚甲基蓝比色法

通过条件实验，利用大气采样器，采集大气中的硫化氢样品，用碱性锌氨络盐吸收藏吸收后，在三氯化铁存在下，与对氨基二甲基苯胺生成亚甲基蓝，比色法定量测定。结果表明，双管连接比单管效果好，吸收液量以每管10mL、采样时间30～40min、采样流量0．5～0．8L／min为佳。     

氢化物发生-分光光度法连续测定砷和铅

本文提出了以氢化物与硝酸银反应为基础的在一份试样溶液中连续测定微量砷和铅的分光光度法。利用硝酸银-聚乙烯醇-乙醇溶液吸收砷化氢显色测定砷,硝酸银-明胶-乙醇溶液吸收铅化氢显色测定铅。方法灵敏快速,通过稀释有色吸收液可测定砷与铅含量相差较大的样品。应用于沉积物和土壤中砷和铅的分析,获得满意的结果。     

Absorption of uranyl ions in cultures of Saccharomices cerevisiae

As part of an extended study of the absorption of uranium in life structures,some experiments on the uranium absorption in cultures of Saccharomices cerevisiaewere carried out. Using the wet ashing Arsenazo III method the absorbed weightof uranium in dregs dry cells was determined.     

Oxidative Coupling of Thiols to Disulfides in Solution with Tripropylammonium Halochromates, (C3H7)3NH[CrO3X], (X = F,Cl) Adsorbed on Alumina

A mild and efficient method for the oxidative coupling of thiols by tripropylammonium fluorochromate and tripropylammonium chlorochromate absorbed on alumina in solution is reported. Alumina absorbed tripropylammonium fluorochromate and tripropylammonium chlorochromate are efficient and new reagents, which are easily prepared and oxidize thiols to the corresponding disulfides quickly. The reactions are clean and readily controlled to stop at the disulfide stage without the formation of common over-oxidized side products. Thus the advantages of the easy procedure and work up, short reaction times, and excellent yields make this a viable alternative method.     

A wet-combustion method for the determination of chlorine in coals

Chlorine in coals can be determined by wet-combustion with sulphuric acid in the presence of potassium dichromate and silver sulphate. The liberated chlorine is absorbed in hydrogen peroxide and after treatment with mercuric oxycyanide is determined acidimetrically. The method is simple, fairly rapid and should be suitable for multiplicate analysis. The results agree well with those given by two independent methods of analysis, i.e. incineration with Eschka mixture followed by the Volhard titration, and the high temperature combustion method.     

离子色谱法测定空气中氨的含量

建立了以稀硫酸吸收、离子色谱法测定空气中氨的方法。该方法可用于环境空气、工业废气中氨的监测。     

Flow/sequential injection determination of gaseous ammonia with a glass diffusion denuder

A new combination of a flow/sequential injection method for the analysis of ammonia has been developed. Gaseous ammonia is selectively absorbed in a phosphoric acid coated glass tube and determined with Berthelot reagents by flow injection. The combination of the gas diffusion denuder sampler with flow injection makes this method very sensitive and selective. The limit of detection of 0.15 mug NH(3).     

Photoacoustic spectroscopy and sorbed-compound luminescence quantum yields

A new method is proposed for determining luminescence quantum yields for sorbed compounds, which is based on comparing photoacoustic signal amplitudes for the specimen and a nonluminescent standard having the same thermal characteristics and used at the same absorbed energy. Fluorescence quantum yields have been determined for some rhodamine dyes sorbed on silica.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 6, pp. 705–711, November–December, 1987.     

Study of size, type and the kerma approximation for thermoluminescent dosimetry

This study aimed to investigate effects of the thermoluminescent dosimeter (TLD) size and type on the absorbed dose value by using of Monte Carlo calculations. The options in creating conditions to establish the kerma approximation were also studied. The Monte Carlo N-Particle (MCNPX 2.4.0) transport code was used to design simulations. Results of this work indicate that if common mineral materials of TLDs are replaced by air and a huge volume is applied for the TLD, the accurate assessment of absorbed doses is possible while the photon energy fluence in the TLD cell is convoluted with mass energy absorption coefficients of the real TLD material. In this method the simulation run-time is strongly decreased.     

Viscoelastic,dielectric, and piezoelectric behavior of solid amylose

Complex elastic, dielectric, and piezoelectric properties were measured on amylose films as a function of temperature and moisture content at 10 Hz. The real part of the complex Young's modulus of films containing a small amount of moisture was larger than that of a dry film. Peaks in the imaginary parts of these complex response functions were observed at about ?80°C. The height of these peaks decreased when the specimen absorbed a little moisture. The activation energy for this peak as determined from an Arrhenius plot of the dielectric frequency dispersion was about 9.5 kcal/mole. This peak was ascribed to methylol rotation. The real part of piezoelectric e constant was shifted downwards when the specimen absorbed moisture. This was attributed to the instantaneous response in the case of a step function excitation. The structure of amylose was thought to be stabilized by moisture absorption, probably due to hydrogen bonding. The mechanism of methylol rotation was examined by dielectric measurements.     

The spectrophotometric determination of arsenic in sea water,potable water and effluents

Procedures are described for the determination of arsenic in sea water, potable waters and effluents. The sample is treated with sodium borohydride added at a controlled rate. The arsine evolved is absorbed in a solution of iodine and the resultant arsenate ion is determined photometrically by a molybdenum blue method. The time required for a complete analysis is about 90 min, but of this only 15 min is operator time. For sea water the range, standard deviation, and detection limit are 1–4 μgl^-1, 1.4 % and O.14 μg l^-1, respectively; for potable waters they are 0–800 μg l^-1, about 1 % (at 20μg l^-1 level) and 0.5μg l^-1, respectively. Silver and copper cause serious interference at levels of 0.5 mgl^-1, and nickel, cadmium and bismuth interfere at concentrations of a few tens of mg l^-1; however, these elements can be removed either by preliminary extraction with a solution of dithizone in chloroform or by ion exchange. Arsenic present in organo-arsenic compounds is not directly determinable, but can be rendered reactive either by photolysis with ultraviolet radiation or by oxidation with permanganate or nitric—sulphuric acid mixture. Arsenic(V) can be determined separately from total inorganic arsenic after extracting arsenic(III) as its pyrrolidine dithiocarbamate into chloroform.     

Spectrophotometric determination of nitrogen in vanadium,titanium and uranium with thymol after alkali fusion

Vanadium metal packed into a nickel boat with potassium hydroxide, is fused at 500–600°C, and the volatilized ammonia is absorbed in dilute hydrochloric acid. The ammonia is converted to monochloramine with sodium hypochlorite at pH 9.8–10.3, and reacted with thymol at pH 11.5–11.9 for 1 h, and the absorbance is measured at 660 nm. The proposed method was also used for the determination of nitrogen in titanium and uranium. Nitrogen in some other metals such as Al, Be, In, Mg, Mn, Si, Sb, Sn, Ta, V, W and Zn which can be fused with potassium hydroxide and have melting points above 400°C may also be determined.