Internal Column Research Articles

Heat transfer and hydrodynamic investigations of a baffled slurry bubble column

Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 µm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed.

Non-extraction HPLC method for simultaneous measurement of dyphylline and doxofylline in serum

A direct injection HPLC method for the simultaneous measurement of dyphylline and doxofylline in serum is reported. Chromatography is carried out with a "Pinkerton" internal surface reversed-phase column and phosphate buffer (0.1 mol/L, pH 6.8) as mobile phase. Absorbance at 275 nm is monitored. Only 10 microL of serum is required to detect less than 1 mg of each drug per liter in biological samples. The standard curve for the method is linear over the range 6-100 mg/L, and precision is acceptable for both drugs, with CVs of 2% and 1.5% for respective concentrations of 6.2 and 25 mg/L. None of the 76 drugs tested for interference affected the measurement of either drug. Four samples can be injected per hour. This method provides a fast, accurate way to monitor two interesting therapeutic agents used in chronic obstructive airway diseases.

Demonstration of the Feasibility of Radially Compressed Microbore HPLC Columns

Abstract This work involved the development of radially compressed, microbore high performance liquid chromatography (HPLC) columns. The design of the overall system and the column are described, and the problems associated with the design features are reported. Variables examined during the course of this work included the column material, column length, packing method, flow rate, radial compression pressure, and internal column pressure. Efficiencies (expressed as plates/meter) are shown for various combinations of those variables and are compared to those obtained using a commercial, steel microbore column.

Bubble properties and mixing characteristics in an airlift bubble column with redistributor

The effects of gas velocity liquid velocity redistributor and their free surface area on bubble properties (size rising velocity size distribution) and mixing characteristics (mixing time circulation time) were studied in an internal airlift bubble column Bubble properties were measured by resistivity probe method, and mixing characteristics were obtained by salt-base impulse method in air-water system. The empirical correlations between bubble properties, mixing characteristics and various operating parameters were proposed The disk type redistnbutor was more effective to redisperse coalesced bubbles than the perforated plate type Especially, the disk type with 19.5% free surface area had given the best result.

Chromatograph with external column evaluated for determining breath hydrogen in clinical studies.

A novel breath-hydrogen analyzer involving an external chromatographic column in the form of a cartridge packed with molecular-sieve material and dessicant is described. The instrument incorporates a sintered SnO2 solid-state sensor into the detector, which registers a change in electrical potential in response to the adsorption of reducing gases; ambient room air is drawn through an activated charcoal filter by a small, internal pump and used as the carrier gas. Once calibrated with a gas of known H2 concentration, a digital meter registers the concentration of H2 in an unknown sample of breath air. The response is linear with concentration up to 160 microL/L. The external column is both necessary and effective for screening out contaminating reducing gases. The correlation coefficient for 250 gas samples measured simultaneously with an external-cartridge instrument and with an internal column chromatography is greater than 0.99. Results by the new analyzer corresponded 100% with those by the conventional machine for detecting carbohydrate malabsorption; for diagnosing efficient carbohydrate absorption, results by the two instruments agreed for 96% of the tests.

Optimum support properties for protein separations by high-performance size exclusion chromatography

Optimum chromatographic properties of high performance size exclusion chromatography (HPSEC) of proteins, such as resolution, molecular weight accuracy and recovery, are obtained on packings and columns with tailor-made physical and chemical structures, employed at properly adjusted eluent compositions and operation conditions. SEC-theory suggests that a broad molecular weight fractionation range and high linearity of the log-linear calibration plot can be achieved by the use of two packings (10- and 80-nm pore size, characterized by a pore-size distribution (psd) equal to or less than 1 decade and by equal internal column porosity (p)), rather than a single 30- to 50-nm pore-size packing with a wide psd. Favourably high-phase ratios of (p)/(o)/ 1.0 for HPSEC columns were accomplished with a minimum interstitial column porosity (o) and a high value for the internal column porosity (p) (the specific pore volume, nu(p), multiplied by the packing density, varrho(p).) Ligands such as diol, N-acetoxyamino and oligomeric ether with a propyl- or propoxy-spacer bonded to the silica at the highest density appear to provide high mass recovery and bioactivity as well as chemical stability. Such packings, available in 3-5 mum particle size ranges of narrow distribution, packed into columns 6 mm i.d. and 500 mm in length, offer the best compromise with respect to resolution, speed and pressure drop. More careful studies are required to explain the effects of protein conformational changes and interconversions during elution on HPSEC columns.

The fate of insulin in cardiac muscle. Studies on isolated muscle cells from adult rat heart.

Isolated muscle cells from adult rat heart were used to study myocardial degradation of insulin and the reactions after the initial binding event. After 60 min of association at 37 degrees C, 90% of specifically bound insulin could be dissociated from the cells; this fraction remained unaltered under steady-state conditions (up to 180 min). To assess the nature of cell-associated radioactivity, cardiocytes were solubilized and filtered on Sephadex G-50. After 5 min of association only intact insulin was observed, whereas under steady-state conditions 4% of 125I-labelled insulin bound to the cells was degraded to iodotyrosine-containing fragments. The Km for insulin degradation by isolated heart cells was estimated to be 1.75 x 10(-7)M. Receptor-mediated insulin degradation was studied by examination of the nature of radioactivity released by the cells after different times of association. After 5 min 83% of dissociating material consisted of intact insulin, whereas this fraction decreased to 50% under steady-state conditions. Treatment of cells with the lysosomotropic agent chloroquine (0.1 mM) significantly decreased the fraction that was eluted at the internal column volume. This study demonstrates that insulin degradation by the heart cell occurs by a receptor-independent and a receptor-dependent mechanism. The latter may involve internalization and a lysosomal pathway.

Criticality Studies for a Neutron Multiplier

Critical experiments were performed on an annular assembly of 9(3.2) wt% /sup 235/U enriched U-Al alloy fuel elements in light water to provide data for the design and operation of a subcritical neutron multiplier of a /sup 252/Cf neutron source. The various factors affecting criticality were determined. In addition to measurement of the critical fuel rod loading under various conditions, values of k/sub eff/ were determined as a function of fuel rod loading by means of pulsed neutron source experiments. The data provide the design basis for operation of the neutron multiplier, yielding a maximum flux value in the internal irradiation column consistent with maintaining a degree of subcriticality in operation.

Isolation and Identification of Drugs of Forensic Interest by High Performance Reverse Phase Ion Pair Partition Chromatography

Abstract A method is presented for the isolation and identification of milligram or microgram quantities of drugs of forensic interest. High performance reverse phase ion pair partition chromatography is performed on a 9.4 millimeter internal diameter microparticulate octadecylsilane column employing a water, methanol, acetic acid, alkylsulfonate mobile phase. Subsequent to collection from the liquid chromatograph, a simple extraction is performed followed by Infrared (IR) analysis and/or solid probe Mass Spectrometry (MS). A study is presented using phenylpropanolamine hydrochloride and ephedrine hydrochloride as a test model for the determination of the optimum concentration of counter ion required for a semi-preparative separation. The method is applied to an LSD seizure from a clandestine laboratory, methamphetamine in a street exhibit, and an amobarbital - secobarbital mixture in a multi-barbiturate capsule.

The barium carbonate procedure for the preparation of glass capillary columns; Further informations and developments

The present second report on the preparation of glass capillary columns, based on producing a crystal layer of barium carbonate on the internal capillary surface, completes the information given in the first report mainly in three directions. First, more practical experience with long term use is presented, showing this column type to be very promising because of universality, durability, simplicity, and efficiency. Second, more insight is given into the underlying processes, as well as into the produced effects. A new aspect concerns the double function of the barium carbonate layer, namly roughening the internal column wall and covering the catalytically active silica surface. Third, more elaborate procedures reducing the particle size of barium carbonate crystals are discussed. On finer particles more homogeneous films, yielding higher separation efficiency, are obtained. Detailed practical directions to new procedures are given.

Preparative gas chromatography in the industrial rubber laboratory

Preparative gas chromatography has been a practical tool to prepare laboratory quantities of highly purified materials. Actual applications have included monomer purification, separation of azeotropic mixtures, resolution of stereoisomers and solvent purification. These separations have been achieved with a modified Prepmaster using a 2.5 inch internal diameter column. Scale-up of analytical resolution to the preparative column was maintained primarily by controlling the radial gas flow distribution. Special insert baffles, were made and installed within the column. Standard liquid phases were used depending upon the separation required. A critical step in the experimental operation is the trapping of the isolated peak. Fogging was prevented by using small water-cooled columns packed with glass beads to maintain the mass transfer rate greater than the heat transfer rate. Each system required somewhat different trapping conditions. Sample sizes ranged from 2 to 25 ml and daily throughput was 10–100 ml depending upon the difficulty of the separation. Material purity greater than 99.9% was usually achieved.

Histology and fine structure of spermatozoa and egg passage in the female tract of Dermacentor andersoni stiles (Acari-Ixodidae)

The final phase of spermiogenesis in the hard tick Dermacentor andersoni occurs in the seminal receptacle of engorged females. This phase is characterized mainly by rupture of the outer sheath of advanced spermatids at their pointed tips, and subsequent elongation as the internal column of these cells evaginates. The sheath invaginates at the opposite end to form the narrow posterior half of the sperm cell. Rupture of the endospermatophoric wall releases the large mass of contained spermatozoa, which begin migration up one or both oviducts. During the migration to the ovarian lumen, spermatozoa exhibit a propensity for active penetration of epithelial cells lining the oviducts. This phenomenon is also observed with spermatozoa in the ovarian lumen. Penetration of epithelial cells by spermatozoa is interpreted to be a response by the latter in seeking eggs for penetration and fertilization.

Punching Failure of Slabs—Transfer of Moment and Shear

A theoretical method of analysis is presented for the calculation of the punching load of an internal column of a flat slab structure subjected to moment and shear transfer. The analytical procedure utilizes elastic thin plate theory and takes into consideration the complex state of stress which exists in the compression zone of the slab around the column periphery. As this prediction is based on lower bound limit analysis a safer estimate than that based on yield line analysis results. A detailed description of the steps involved in the analysis is given in a flow diagram which indicates that four different modes of failure are possible. The validity of the assumptions made is checked by comparing the predicted punching loads with those obtained from tests that are reported in the literature. This method will be of value in supplementing existing empirical procedures.

Analysis of slab and girder bridges by the finite strip method

The finite strip method is used for the analysis of simply-supported and continuous slab girder bridge decks of constant width. New features presented herein include the derivation of the stiffness matrix of a beam and its coupling with strips, the derivation of the stiffness matrix of a strip with longitudinal variation in thickness, and the analysis of bridges with discrete internal column supports. The finite strip method requires the operation on narrow-band matrices of small order which can be easily carried out on a small capacity computer, and the computations involved are remarkably less than in other methods. Some of the results obtained by this method are verified by model testing while other results are compared with “exact” or approximate solutions. Good agreement has been observed for all cases.

Vibration of a Cylindrical Shell in an Acoustic Medium

In this paper is considered the response to forced vibration of an infinitely long thin cylindrical shell, surrounded by a fluid extending to infinity and containing the fluid. When the fluid is air, there are resonant frequencies close to (1) the natural frequencies of the shell in a vacuum, and (2) the natural frequencies of the internal column of fluid. Numerical results show the variation of these resonant frequencies with the number of circumferential waves, the ratio of the axial wavelength to the mean radius of the shell and the ratio of the thickness to the mean radius. With water as the fluid, the resonant frequencies show considerable divergence from the natural frequencies of the shell in a vacuum. The application of the results to shells of finite length is discussed.

Determination of the Neutron Temperature at the Center of the Thermal Test Reactor

The effective temperature of the thermal neutrons at the center of the internal column of the Thermal Test Reactor has been measured by means of a danger coefficient technique. Assuming that the th...