Miniaturization of separation techniques using planar chip technology

Miniaturization of separation columns implies equally reduced vol- umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron-sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser-induced fluorescence detection at any capillary length of choice between 5 and 50 mm.     

Prediction of the net retention volumes in gas chromatography using porous polymers coated with different stationary phases

Summary A new expression which permits the prediction of the net retention volumes in gas chromatography with column packings of coated porous polymers is reported. The porous polymers Chromosorb 101 and Chromosorb 102 were used as supports and squalane, Ethofat and Carbowax 20M as stationary phases at three different column temperatures of 80°C, 100°C and 150°C. Several organic compounds of various polarity were used as test compounds and the net retention volumes, V_Ntheor, have been calculated according to this new expression. The V_Ntheor values were compared with the experimental net retention volumes, V_Nexp, and it was found that the difference between these two values is dependent on the type of compound and column packing. Nevertheless, the elution order could be predicted in most cases.     

Excess Molar Volume and Viscosity of Isobutyric Acid + Water Binary Mixtures Near and Far Away from the Critical Temperature

The excess molar volume V^E, shear viscosity deviation Δη and excess Gibbs energy of activation ΔG^∗E of viscous flow have been investigated by using density (ρ) and shear viscosity (η) measurements for isobutyric acid + water (IBA+W) mixtures over the entire range of mole fractions at five different temperatures, both near and close to the critical temperature (2.055K ≤ (T−T_c)≤ 13.055K). The results were also fitted with the Redlich–Kister equation. This system exhibited very large negative values of V^E and very large positive values of Δη due to increased hydrogen bonding interactions and correlation length between unlike molecules in the critical region and to very large differences between the molar volumes of the pure components at low temperatures. The activation parameters ΔH^∗ and ΔS^∗ have been also calculated and show that the critical region has an important effect on the volumetric properties.     

The ionization of perchloric and hydrofluoric acids in aqueous solution

Cyclical bifurcated hydrogen bonded structures are proposed for aqueous solutions of hydrofluoric acid and for the bifluoride ion which are consistent with the spectral data. The structure proposed for HF is also applicable to solutions in organic solvents. Raman spectra of tetramethylguanidinium perchlorate suggest that the corresponding Raman spectra of perchloric acid solutions may not be interpreted in terms of a completely dissociated acid. Other evidence including activity coefficient, heat capacity and partial molal volume data suggest that there is some association in relatively dilute perchloric acid solutions between the perchlorate ion and the hydrated proton. This association decreases in concentrated aqueous solutions.     

Volumes,heat capacities and solubilities of amyl compounds in decyltrimethylammonium bromide aqueous solutions

Apparent molar heat capacities and volumes of amylamine (PentNH₂) 0.02m, capronitrile (PentCN) 0.02m and nitropentane (PentNO₂) 0.009m in decyltrimethylammonium bromide (DeTAB) micellar solutions, in water and in octane were measured at 25°C. By assuming that their concentration approaches the standard infinite dilution state, heat capacities and volumes were rationalized by means of previously reported equations following which the distribution constant between the aqueous and the micellar phase and heat capacity and volume of the additives in both phases are simultaneously derived. The present results are compared to those we have previously obtained for pentanol (PentOH). The thermodynamic properties of PentNH₂ in water and in micellar phase are substantially identical to those of PentOH but different from those of PentCN and PentNO₂ whereas the opposite behavior was observed in their pure liquid state and in octane. The nature of the solvent medium seems to affect the thermodynamic behavior of PentNH₂. Also, the study of the apparent molar heat capacities of the amyl compounds investigated here in micellar solutions as a function of surfactant concentration shows evidence of a maximum at about 0.4m DeTAB, which can be attributed to a micellar structural transition. Accordingly, the solubilities of PentCN and PentNO₂ as a function of the DeTAB concentration drop in the neighborhood of the concentration where heat capacities display the maximum.     

Density and Sound Velocity Studies of Aqueous Solutions of Tetradecyltrimethylammonium Nitrate at Different Temperatures

The density and ultrasound velocity of aqueous solutions of tetradecyltrimethylammonium nitrate were measured in the temperature range of 15 to 35°C in 5°C intervals. The concentration range covered the premicellar and micellar regimes. By assuming a pseudophase separation model for the micellar system, we applied the densitometric data to estimate the apparent molar volumes and the apparent thermal expansibility coefficients of the surfactant in monomeric and micellar forms. Ultrasound velocity and density data enabled us to estimate the isentropic compressibility of the surfactant in both forms. The results are compared with relevant literature data for alkyltrimethylammonium bromides.     

Volume and heat capacity of model non-aqueous self-assembly systems

Blends of immiscible polymers are often stabilized by block copolymers which can form non-aqueous micelles and microemulsions in the liquid polymers. The phase diagrans, apparent volumes and apparent heat capacities of model non-aqueous binary and ternary systems were studied in order to investigate the conditions under which such self-assembly systems could form. 1,2-Hexanediol, which can cosolubilize hexane and ethyleneglycol, forms inverse micelles in hexane and weak microaggregates in ethyleneglycol. Genapol X-060, a commercial alcoholic surfactant containing on the average an aliphatic chain of 13 carbons and 6 oxyethylenes (C₁₃E₆), forms microaggregates in poly(ethyleneglycol) 400. These self-assembly systems are strengthen in the presence of a third component which has an affinity for the inner phase.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

A simple flow injection-reduced volume column system for hemoglobin typing

A flow injection (FI)-reduced volume column system was developed for hemoglobin (Hb) typing to be used as an initial screening method for thalassemia. The column was packed with 140 μl diethylaminoethyl (DEAE)-Sephadex A-50 ion exchange beads. Hb can be separated using Tris–HCl buffer solution with pH gradient 8.5–6.5 and then monitored spectrophotometrically at 415 nm. The hemolysate of 40 blood samples from packed red cells were screened for thalassemia by determining the amount of HbA₂ and HbE present. The proposed system was able to predict positive test results from those samples with β, E-trait and EE homozygous thalassemia, Hb types that were independently identified following the conventional method at the hospital laboratory. Advantages of the proposed system over the conventional column technique include low amount of reagents and blood sample needed, short analysis time and low cost. Each analysis required only 80 μl of 50 times diluted packed cells, which is equivalent to 1.6 μl undiluted packed cells, and it can be completed in only 35 min. This simple FI-reduced volume column system was demonstrated to be an economic alternative system for Hb typing to initially screen some types of thalassemia such as β-trait, E-trait and EE-homozygous which are commonly found in Thailand.     

Calculation of the van der Waals volumes of organic molecules

A new and more precise method is proposed for calculating van der Waals atomic and molecular volumes of organic compounds. The method provides for intersections of three or more spheres at one point of space. Such a possibility is essential for calculating the volumes of sterically overcrowded molecules and of molecules with intramolecular hydrogen bonds. A computer program for IBM PC/AT(XT) is developed. Depending on the atomic environment in the molecule, the average values of the volume increments for atoms C, N, O, H, F, Cl, and S are obtained using the data from the Cambridge Structural Database.N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow 117071. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 922–931, April, 1992.     

不同温度下氨基酸在α-咖啡碱水溶液中的体积、粘度及折光率特性

Measurements of density(ρ), viscosity(η), and refractive index(n), were carried out on α-amino acids, DL-solution at 298.15, 303.15, 308.15, and 313.15 K. These measurements have been carried out to evaluate some important parameters, viz., apparent molar volume (φv), partial molar volume (φv0), transfer volume (φ0v (tr)), viscosity A and B coefficients of Jones-Dole equation, free energies of activation per mole of solvent (△μ0#1) and solute (△μ0#2),enthalpies (△H*) and entropies (△S*) of activation of viscous flow, variation of B with temperature ((a)B/(a)T)P, and molar refractive index (RD). These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.