Measurement of lactate in whole human blood with near-infrared transmission spectroscopy

We have evaluated the potential of near-infrared spectroscopy (NIRS) as a technique for rapid analysis of lactate in whole blood. To test the NIRS technique, a comparison was made with a standard clinical method using whole blood samples taken from five exercising human subjects at three different stage of exercise. To expand lactate concentration within the physiological range, standard additions method was used to generate 45 unique data points. Spectra were collected over the 2050-2400 nm spectral range with a 1 mm optical path length quartz cell. Reference lactate concentrations in the samples were determined by enzymatic measurements. Estimates and calibration of the lactate concentration with NIRS was made using partial least squares (PLS) regression analysis and leave-N-out cross validation on second derivative spectra. Separate calibrations were determined from each of the subject samples and cumulative PRESS was used to determine the number of PLS factors in the final model. The results from the PLS model presented are generated from the five individual calibration coefficient vectors and provided a correlation coefficient of 0.978 and a standard error of cross validation of 0.65 mmol l⁻¹ between the enzymatic assay and the NIRS technique. To study the parameters that impact the spectra baseline and the correlation between the calculated model and the data, referenced measurements of lactate against baseline spectrum were made for each individual. A correlation coefficient of 0.992 and a standard error of cross validation of 0.21 mmol l⁻¹ were found. The results suggest that NIRS may provide a valuable tool to assess physiological status for both research and clinical needs.     

Adsorption of p-Nitrophenol in Untreated and Treated Activated Carbon

The adsorption of p-nitrophenol in one untreated activated carbon (F100) and three treated activated carbons (H₂, H₂SO₄ and Urea treated F100) was carried out at undissociated and dissociated conditions.To characterize the carbon, N₂ and CO₂ adsorption were used. X-ray Photoelectron Spectroscopy (XPS) was used to analyze the surface of the activated carbon.The experimental isotherms are fitted via the Langmuir homogenous model and Langmuir binary model. Variation of the model parameters with the solution pH is studied. Both Q _max and the adsorption affinity coefficient (K ₁) were dependent on the PZC of the carbons and solution pH. The Effect of pH must be considered due to its combined effects on the carbon surface and on the solute molecules. Adsorption of p-nitrophenol at higher pH was found to be dependent on the concentration of the anionic form of the solute.     

Thermal And Structural Characterization of Commercial α-, β-, and γ-Cyclodextrins

α-, β-, and γ-cyclodextrins (CDs) marketed by five different companies were characterized from the thermal and structural point of view. Three αCD samples showed two-step DSC dehydration profiles and their XRD patterns were characteristic for αCD⋅6H₂O form I, whereas one brand with an apparent three-step DSC dehydration behaviour was a mixture of αCD⋅6H₂O form I and anhydrous αCD. The differences in the DSC profiles after dehydration and EGA onset decomposition temperatures recorded for the five βCD brands were attributed to different manufacturing and purification processes. The five γCDs brands showed a common thermal behaviour and very similar XRD patterns. The patterns did not match the idealized pattern of γCD⋅14.1H₂O, indicating the occurrence of two different hydrated crystal structures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermodynamic properties of peptide solutions: 7. Partial molar isentropic pressure coefficients of some dipeptides in aqueous solution

The partial molar isentropic pressure coefficients at infinite dilution, K _S,2 ^o , have been determined for a number of dipeptides in aqueous solution at 25°C. For a series of dipeptides of sequence gly-X, where X is an amino acid with a neutral side chain, the K _S,2 ^o values are all more negative than that for diglycine. The results are discussed in terms of the hydration of the side chains. There are significant differences in the K _S,2 ^o values for sequence isomeric dipeptides. These differences can be rationalized in terms of the mutual interactions between the side chain and the ionic end groups in the dipeptides. Possible relationships between K _S,2 ^o and V ₂ ^o , the partial molar volume at infinite dilution, were investigated. For the dipeptides of sequence gly-X there is an interesting linear relationship between K _S,2 ^o /V ₂ ^o and V ₂ ^o .     

Electrical Double Layer on Liquid Sn–Ga Alloy in Aqueous Solutions

Double-layer parameters of a liquid Sn–Ga electrode in aqueous electrolyte solutions are studied. It is shown that Sn in the alloy with Ga is a surface-active component and is forced out onto a surface layer of the electrode. The double-layer parameters of an Sn–Ga electrode (8 at. % Sn), which are measured in the experimentally accessible range of charges, differ radically from the parameters of Ga electrodes and are close to those of Sn electrode. Hence, an Sn–Ga electrode containing 8 at. % Sn simulates electrochemical properties of a liquid Sn electrode. The difference between reciprocal electronic capacitances of Hg and Sn and a corrected electrochemical work function of Sn are determined. It is shown that the chemisorption interaction of an Sn–Ga electrode with water molecules is virtually absent at charges more negative than –7 C/cm². A potential drop on uncharged Sn, which is associated with water chemisorption, is –20 mV. Thus, the hydrophilicity of Sn is slightly higher than that of Hg, Bi–Ga, Pb–Ga, and Tl–Ga and significantly lower than that of In–Ga, Cd–Ga, and Ga.     

Thermodynamic issues associated with combined cyclic voltammetry and wafer curvature measurements in electrolytes

A thermodynamic framework has been provided for the interpretation of combined cyclic voltammetry and surface stress measurements, the latter being obtained from wafer curvature or beam deflection measurements of a solid electrode as a function of applied potential (so-called voltstressograms). Firstly, the derivation of electrocapillarity equations for solid electrodes has been critically reviewed by starting from the Gibbs adsorption equation appropriate for solid–electrolyte interfaces. This allowed us to demonstrate the critical importance of elastic surface strain in the thermodynamic boundary conditions of the partial derivatives intervening in the interpretation of voltstressograms. From these considerations, it was shown for the first time that the electrocapillarity equations for solid electrodes are not appropriate for describing the variation of surface stress with potential obtained from wafer curvature measurements, because such measurements are intrinsically incompatible with the constant strain condition implied in the electrocapillarity equations. An alternative explanation is provided for the experimentally observed proportionality between the current density, measured in cyclic voltammograms, and the first derivative of surface stress with respect to potential, obtained from voltstressograms.     

PSRK: A Group Contribution Equation of State Based on UNIFAC

A group contribution equation of state called PSRK (Predictive Soave-Redlich-Kwong) which is based on the Soave-Redlich-Kwong equation (Soave, 1972) has been developed. It uses the UNIFAC method to calculate the mixture parameter a and includes all already existing UNIFAC parameters. This concept makes use of recent developments by Michelsen (1990b) and has the main advantage, that vapor-uquid-equilibria (VLB) can be predicted for a large number of systems without introducing new model parameters that must be fitted to experimental VLB-data. The PSRK equation of state can be used for VLB-predictions over a much larger temperature and pressure range than the UNIFAC γ--approach and is easily extended to mixtures containing supercritical compounds. Additional PSRK parameters, which allow the calculation of gas/gas and gas/alkane phase equilibria, are given in this paper. In addition to those mixtures covered by UNIFAC, phase equilibrium calculations may also include gases like CH₄ C₂H₆, C₃H₆, c₄H₁₀, CO₂, N₂, H₂ and CO.     

乙醇-环己烷体系中NaI活度系数的测定与计算

由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一…     

Synthesis and characterization of macrocyclic vinyl aromatic polymers

The synthesis and characterization by size exclusion chromatography, liquid chromatography, NMR, matrix‐assisted laser desorption/ionization, thermal analysis, and other techniques of well‐defined and narrow molecular weight distribution macrocyclic polystyrene (PS), poly(2‐vinylpyridine), poly(α‐methylstyrene), poly (2‐vinyl‐naphthalene) (P2VN), and poly(9,9‐dimethyl‐2‐vinylfluorene) (PDMVF) containing a single 1,4‐benzylidene, methylidene, or 9,10‐anthracenylidene unit are reviewed. The absorption and emission spectroscopy of PS, P2VN, and PDMVF is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2139–2155, 2006