Fluorometric assay of ultramicro quantities of glucose with somogyi filtrate and hexokinase

A procedure is described for the determination of glucose in 3 μl of serum or plasma. It is based on the phosphorylation of glucose with ATP mediated by hexokinase. The TPNH generated with glucose-6-phosphate dehydrogenase is measured fluorometrically.Sensitivity is greatly improved over the corresponding procedure using UV absorption for the determination of NADPH. Bilirubin does not interfere. Interference from hemolysis is eliminated by precipitation with Zn(OH)₂ Blood taken with fluoride can be utilized. Fluoride interference is removed with the Zn(OH)₂ and with excess Mg in the substrate. Positive interference by fructose is negligible with some enzyme preparations but is appreciable with others.The results correlate well with those obtained with an ortho toluidine method, after protein precipitation with trichloroacetic acid. The method is especially useful in the Pediatric Laboratory.     

Thermodynamic parameters of solvation of nonelectrolytes in aqueous solutions of amides of carboxylic acids

Interaction and reorganization contributions to solvation enthalpies of nonelectrolytes in aqueous solutions of amides of carboxylic acids with different degree of N-substitution and N-methylpyrrolidone are calculated. The data are discussed using structurally thermodynamic characteristics of water-amide systems obtained by us previously. It is found that the type of concentration dependence of the solvation enthalpy of nonelectrolytes in all solutions investigated is determined by the type of reorganization component. It is shown that the highest solvation exothermicity of nonelectrolytes in water is due to the lowest value of the reorganization contribution in spite of that nonelectrolytes interact weaker with water than with non aqueous components.     

Solid-state NMR spectroscopic study of the structure of grafted layers of phosphonic acid ester-modified hydroxyapatite

Interaction of hydroxyapatite (HAP) surface with phosphonic acid esters is studied under different conditions. The urgency of the study is due to the fact that HAP is one of the main components of bone tissue and is widely applied in the production of materials designed for filling bone defects. Modification of the surface properties of HAP may result in the development of materials with increased biocompatibility. It is revealed that, in the absence of solvents or in the medium of an aprotic solvent, phosphonic acid esters interact with HAP surface to yield pyrophosphate groups. The interaction with the surface does not take place in the presence of protic solvents.     

Influence of the polarity of the microenvironment of pyrene on the intensity of its solid-phase luminescence

The sorption of pyrene by a filter paper modified with lead acetate is studied by luminescence methods. Based on changes in the vibrational structure of fluorescence spectra of pyrene, it was found that the polarity of the microenvironment of pyrene adsorbed from solutions in ethanol increases with the concentration of acetic or hydrochloric acid in these solutions. It was revealed that, when an acid is added, pyrene fluoresces and phosphoresces more intensely at room temperature. It is shown that this is associated with a more efficient sorption of pyrene by the filter paper from acid solutions in ethanol.     

Photometric complex-formation titrations of submicromole amounts of metals in the presence of an approximately equivalent amount of indicator

The photometric titration of the metal indicator complex MI with a ligand L is discussed. A tangent procedure is adopted for the determination of the end-point. From this procedure, in combination with an assumed maximum titration error, titration conditions have been derived. A procedure is introduced which, in conjunction with the derived titration conditions, permits the selection of a suitable titration medium by means of a diagram in which log K, log alpha and log chi are plotted vs. pH. The procedure is applied to determination of lead and zinc in the presence of citric acid, the medium used for their paper-electrophoretic separation. The use of citric acid introduces some limitations; it is shown that the method developed is generally applicable.     

A collaborative study of four methods of assay of benzylpenicillin

The assay of benzylpenicillin by iodimetric titration, spectrophotometry with a mercury(II) chloride—imidazole reagent, titration with mercury(II) nitrate in acetate buffer solution, and titration with mercury(II) perchlorate in aqueous pyridine solution, was examined in four laboratories. The first two methods were applied to two samples (the third one being the reference sample), the mercury(II) nitrate titration to three, and the mercury(II) perchlorate method to two samples. The four methods gave very similar results, but the purity obtained with the mercury(II) perchlorate method was slightly lower, and this procedure is less desirable because pyridine is used as solvent. There were no great differences in the relative standard deviations of the four methods. The titration with mercury(II) nitrate is preferred because it is an absolute method.     

Vinylation of silanes and disiloxanes. Preparation of hexavinyldisiloxane

Vinylation of silanes and disiloxanes has been studied. It has been shown that in the reactions of silanes with vinyl chloride and magnesium or sodium the sole product formed is tetravinylsilane. In the reactions of hexaethoxydisiloxane with vinyl chloride and magnesium, tetravinylsilane is the sole product formed. Hexavinyldisiloxane with yield up to 85% is formed in the reaction of hexaethoxydisiloxane with vinyl chloride and magnesium in the presence of copper(II) salts as alkylation catalyst.     

Dependence of the Rate of Electrodeposition of Metals at Mono- and Multielectrodes on Voltage in the Case of an Exaltation Mechanism of Mass Transport

Dependences of the rate of copper deposition on mono- and multielectrodes out of dilute solutions of acetic acid at voltages of 20–250 V are compared. It is established that the same rate of deposition in the case of a multielectrode (25 electrodes with a diameter of 0.1 mm) takes place at a voltage that is lower by 2.7 times than that in the case of a monoelectrode with a diameter of 0.5 mm and the same area. The same results are obtained during electrodeposition of cadmium and thallium. In order to explain this effect, a two-layered model of potential distribution is suggested. In accordance with this model, the resistance of electrolyte in the vicinity of a multielectrode is equal to the sum of the resistance of the layer nearest to the electrode (where it is determined by the sum of conductances to each microelectrode) and the external layer, where the potential distribution is close to hemispherical. It is shown that calculations in accordance with this model allow one to give an estimate of the effect's scale that agrees with experiment and to predict its possible limits following an increase in the number of electrodes that make up a multielectrode.     

Potentiometric determination of free acidity in presence of hydrolysable ions and a sequential determination of hydrazine

A simple potentiometric method for the determination of free acidity in presence of hydrolysable ions and sequential determination of hydrazine is developed and described. Both free acid and hydrazine are estimated from the same aliquot. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 1.2% relative standard deviation. Hydrazine content has also been determined in the same aliquot with a recovery of nitric acid is 99% with 2% relative standard deviation. The major advantage of the method is that generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal.     

Quenching of fluorescence of solutions of polystyrene and copolymers with methyl methacrylate

Quenching of excimer fluorescence from polystyrene and monomer emission from 5 and 10% methyl methacrylate copolymer with styrene has been studied in solution using dibromoethane and iodine as quenching species. From the measured rate constants along with polarization measurement of the emissions, it is concluded that energy migration does not occur in dilute solution of polystyrene. It is proposed that excimer is formed by rotation of a pendant, excited phenyl group with a face-to-face conformation with its nearest neighbour.     

Kinetics and mechanisms of the oxidation by permanganate of L-Phenylalanine

The oxidation of L-Phenylalanine by permanganate ion in aqueous phosphate buffers is autocatalized by the inorganic reaction product, which is stabilized in solution by adsorption of phosphate ions on its surface. This product is a soluble form of colloidal manganese dioxide. The rate of the noncatalytic reaction pathway is first-order in both the oxidizing and reducing agent. It is not affected by potassium chloride addition to the solution, but by phosphate addition. The rate increases with the pH of the medium. The autocatalytic pathway is first-order in both permanganate ion and colloidal manganese dioxide, (the permanganate ion according to the Langmuir isotherm). The autocatalytic rate increases with reductant concentration (follows the Langmuir adsorption isotherm). It is not affected by potassium chloride addition to the solution, whereas an increase in the phosphate concentration results in an increase in the rate with the same pH of the medium. Mechanisms consistent with the experimental data are proposed.     

Effect of hydrodynamic conditions of the kinetics of Bentonite Suspension Flocculation by Cationic Polyelectrolytes and the strength of formed flocs

The influence of Zetag and SNF FO cationic polyelectrolytes on the aggregation kinetics of bentonite particles in a flow system is studied in detail as a function of the dose of added polymer, charge density of its macromolecules, the regime and intensity of system stirring, and the type of stirrer (magnetic and mechanical stirrers). It is shown that there is an optimal regime, namely, the alternation of slow and rather rapid stirring, that provides the formation of the largest and strongest flocs. The rate of aggregation and the size of formed flocs increase with the amount of added reagent irrespective of the intensity of system stirring, as well as with an increase in the charge density of polyelectrolyte, which is responsible for the affinity of macromolecules for the surface. The effect of polymer charge on the flocculation kinetics is exhibited first of all upon the slow stirring of suspension. The difference in the sizes of aggregates resulted from the flocculation of macromolecules with different charges is leveled with an increase in stirring intensity. An empirical method for comparing the efficiency of the flocculating action of polymers in suspensions prepared using different types of stirrers is proposed.     

Dependence of the enthalpies of formation of glycylglycinate complexes of nickel(II) on the composition of a mixed water-dimethylsulfoxide solvent

The heat effects of the complexation reactions of nickel(II) with a glycylglycinate ion in a water-dimethylsulfoxide solvent in a range of compositions of 0.00–0.60 molar parts of dimethylsulfoxide (DMSO) (an ionic strength of 0.1 was maintained using sodium perchlorate) were determined by means of calorimetry at 298.15 K. It is established that the exothermicity of complexation reactions rises by the first two steps and falls upon the addition of a third glycylglycinate anion with an increase in the concentration of DMSO. It is shown that the formation of mono- and bis-glycylglycinate complexes of nickel(II) in a water-DMSO solvent is determined mostly by the enthalpic contribution. It is concluded that the formation of tris-ligand complexes is more associated with the entropic contribution.     

用红外光谱法测定环烷酸纯度的研究

环烷酸是一类带有碳环结构的一元羧酸,是以各种不同分子量的一元羧酸的混合物存在于石油中．将石油各馏分精炼过程的碱洗废液,经过酸处理,就制得工业环烷酸．工业环烷酸中环烷酸含量是环烷酸最重要的一个理化指标,在红外光谱上,环烷酸的羧基在1700cm^-1附近有一极强的特征吸收峰,并且吸收不受样品中其它组分的干扰．因此,红外光谱是快速准确测定工业环烷酸中环烷酸含量较为理想的方法．     

Non-Steady-State Temperature Field of the Vapor-Gas Mixture in the Vicinity of a Growing Droplet: Balance of the Heat of Phase Transition

The non-steady-state temperature field of the vapor-gas medium in the vicinity of a droplet growing in supersaturated vapor is constructed. In the conduction problem, a time-dependent boundary condition is used which ensures the fulfillment of the balance condition of the heat of phase transition. The resultant temperature field is compared with the one obtained in the heat conduction problem with the equilibrium boundary condition on the surface of a droplet of a fixed radius. Although the solution with the equilibrium boundary condition does not ensure the balance between the heat released on the growing droplet and the heat distributed due to heat conduction in the vapor-gas medium, the difference between the two solutions is not very large. This difference is important for describing the homogeneous nucleation of supersaturated vapor in the vicinity of a growing droplet, as is indicated by comparison of the vapor supersaturation fields constructed with and without allowance for thermal effects, as well as with the use of solutions to the diffusion and heat conduction problems with various boundary conditions.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 333–341.Original Russian Text Copyright © 2005 by Grinin, Zhuvikina, Gor.     

Numerical simulation of phase separation of immiscible polymer blends on a heterogeneously functionalized substrate

The spinodal phase decomposition of an immiscible binary polymer blend system is investigated with numerical models in two-dimensional and three-dimensional (3D). The effect of the elastic energy is included. The mechanism of the evolution of the phase separation is studied and the characteristic length R(t) is shown to be proportional to t(13). In the case when the phase separation is directed by a heterogeneously functionalized substrate, the increase in the characteristic length is divided into two stages by a critical time. The R(t) approximately t(13) diagram can be fitted with a straight line in both the first and second stages. The slope of the fitting line significantly decreases after the critical time. The compatibility of the resulting pattern to the substrate pattern is also measured by a factor C(S). It is observed that there is also a critical time in the evolution of the compatibility for the cases with and without elastic energy. The critical time of C(S) is identical with the respective critical time of R(t). The lateral and vertical composition profiles functionalized substrate is observed with the 3D model. The difference mechanism of the cases with and without elastic energy is discussed.     

A comparison of the effects of chemisorbed sulfide ions on the electrochemical behavior of gold and silver in thiourea electrolytes

It is shown that, in the case of gold, the catalytic activity of sulfur adatoms is significantly higher in the anodic dissolution of metal than in its deposition. In both processes, the catalytic activity increases with increasing overvoltage. The catalytic activity of sulfur adatoms is considerably lower for silver than for gold both in the metal deposition and dissolution, and it is virtually independent of overvoltage. In the case of silver, the catalytic activity of sulfur adatoms in the electrodeposition is slightly higher than in the metal dissolution. There results are compared with the action of heavy metal adatoms on the dissolution and deposition of gold and silver in the cyanide solutions. It is shown that the above regularities are qualitatively true for both systems. The main distinction is that the catalytic activity of sulfide ions in the thiourea solutions reaches a plateau with increasing surface coverage with sulfur adatoms, whereas the activity of heavy metals passes through a maximum with increasing surface coverage. The results are explained in view of earlier determined regularities of kinetics of electrode processes in these systems and the effect of electrocatalysis on these regularities.     

部分水解聚丙烯酰胺浓度对结构形貌的影响

本文用原子力显微镜(AFM)研究了不同浓度的部分水解聚丙烯酰胺(HPAM)溶液在云母片上成膜后的结构形貌。浓度不同,AFM下观察到的结构形貌差别很大。50ppm和1000ppm的HPAM在云母片上成膜后不能形成规则的排列,而100ppm的HPAM在云母片上成膜后形成规则的排列,但不同位置处的排列不同,500ppm的HPAM在云母片上成膜后可形成树枝生长的分形结构。     

Elimination of oxidative degradation during the per-O-methylation of carbohydrates

The possible oxidative degradation mechanism occurring during the per-O-methylation of carbohydrates in dimethyl sulfoxide with methyl iodide in the presence of base is described. Evidence is presented that this process occurs only under anhydrous conditions when there is a long reaction time between the carbohydrate dissolved in dimethyl sulfoxide and methyl iodide, followed by reaction with the base. Under these specific conditions, the oxidative degradation of alditols, and cyclic carbohydrates, with and without a free hemiacetal group, is observed. The reaction between carbohydrate and methyl iodide in dimethyl sulfoxide can result in a complete oxidative degradation depending on the type of carbohydrate and the time of reaction. The oxidative degradation can be accelerated by replacing methyl iodide with dimethyl sulfate. Mass spectrometric identification of the degradation products of d-glucitol indicates simultaneous oxidation processes at all the hydroxyl groups, with site dependent rates of their reactivity. This oxidative process is not a characteristic of the methylation of carbohydrates in dimethyl sulfoxide with methyl iodide in the presence of solid sodium hydroxide and can be totally avoided by treating the carbohydrate with powdered sodium hydroxide before introduction of methyl iodide under nonanhydrous conditions, or by adding a trace of water in dimethyl sulfoxide before methyl iodide, or by using N,N-dimethylacetamide as the solvent. The degradation of the per-O-methylated carbohydrates in the liquid-liquid extraction process is also taken into account, and it is found that the degradation process can be avoid by neutralization of the base before extraction, by using benzene or tetrachloromethane as extraction solvent, and by drying the final organic extract.     

The effect of reaction time on the chain structure of poly(p-phenylene) and a study of doping with FeCl3

This paper deals with the relation between polymerization time and poly(p-phenylene) (PPP) yield in the synthesis of PPP by the Kovacic method. It is found that the reaction is uniform in the polymerization time range of less than 2 hr, with a PPP yield of up to about 60%, and then the yield increases a little with an increase of polymerization time. It has been found from the infrared spectra that the mainchain structure of PPP obtained from different polymerization times is exactly the same without orthoand meta-polymers. However there is a chlorine substitution for hydrogen on the phenyl rings, and the substitution quantity increases with the extension of reaction time. The reason why there is a great difference in conductivity appears with FeCl₃ doping is also studied, and we find it is related to different degrees of rinsing in the doping process.