Modeling and optimization for separation of ionic solutes in pressurized flow capillary electrochromatography

By manipulation of applied pressure or voltage, pressurized flow capillary electrochromatography (P-CEC) permits unique control of selectivity for ionic solutes. A simple mathematical model has been developed to describe the quantitative relationship between the electrochromatographic retention factor (k(*)) of charged solutes and the applied voltage and pressure. The validity of the model was verified experimentally with hydrophilic interaction mode CEC (HI-CEC). On the basis of the model developed, it was found that the value of k(*) could be predicted accurately using only a limited number of data points from the initial experiments at different voltages or pressures. Correlation between the experimentally measured and calculated k(*) was excellent, with a correlation coefficient greater than 0.999. Optimization for the separation of peptides by P-CEC was also performed successfully on the basis of the proposed model.

Miniaturized tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection cell for capillary electrophoresis and flow injection analysis

The design and performance of a miniaturized chip-type tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] electrochemiluminescence (ECL) detection cell suitable for both capillary electrophoresis (CE) and flow injection (FI) analysis are described. The cell was fabricated from two pieces of glass (20 x 15 x 1.7 mm), and the 0.5-mm-diameter platinum disk was used as working electrode held at +1.15 V (vs silver wire quasi-reference), the stainless steel guide tubing as counter electrode, and the silver wire as quasi-reference electrode. The performance traits of the cell in both CE and FI modes were evaluated using tripropylamine, proline, and oxalate and compared favorably to those reported for CE and FI detection cells. The advantages of versatility, sensitivity, and accuracy make the device attractive for the routine analysis of amine-containing species or oxalate by CE and FI with Ru(bPY)(3)(2divided by) ECL detection.

Electrocatalytic oxidation of hydrazines at a 4-pyridyl hydroquinone self-assembled platinum electrode and its application to amperometric detection in capillary electrophoresis

4-Pyridyl hydroquinone on a platinum electrode adsorbs through the pyridine nitrogen forming stable self-assembled layers. The electrocatalytical oxidation of hydrazines was performed by the modified electrode. The overpotential of hydrazines was decreased markedly at the self-assembled monolayer (SAM) electrode. The mechanism of hydrazine oxidation was also investigated. Amperometric detection of hydrazine under zero potential (vs Ag\AgCI\sat. KCl) was exhibited by the SAM electrode used as an electrochemical detector in a flow system. (C) 1998 Elsevier Science S.A. All rights reserved.

Through the portal – improving the flow of information on non-native marine species in Great Britain.

Abstract: The UK Government funded, GB Non-Native Species Information Portal (GBNNSIP) collects and collates data on non-native species in Great Britain making information available online. Resources include a comprehensive register of non-native species and detailed fact sheets for a sub-set, significant to humans or the environment. Reporting of species records are linked to risk analyses, rapid responses and horizon scanning to support the early recognition of threats (Figure 12). The portal has improved flow of new and existing distributional data to the National Biodiversity Network (NBN) to generate distribution maps for the portal. The project is led by the Biological Records Centre and the Marine Biological Association is responsible for marine non-native species within this scheme. The INTERREG IV funded project Marinexus has included professional research and citizen science work, which has fed directly into the portal. The portal outputs and the work of Marinexus have a range of marine governance applications, including supporting work towards MSFD compliance.

Analysis of the Steady Flow Characteristics Through a Poppet Valve

This paper describes the flow characteristics in the near throat region of a poppet valve under steady flow conditions. An experimental and theoretical procedure was undertaken to determine the total pressure at the assumed throat region of the valve, and also at a downstream location. Experiments of this type can be used to accurately determine the flow performance of a particular induction system. The static pressure recovery was calculated from the near throat region of the valve to the downstream location and was shown to be dependant on valve lift. Total pressure profiles suggest that for this particular induction system, the majority of pressure loss occurs downstream of the valve for lift/diameter ratios up to 0.1, and upstream of the valve for lift/diameter ratios greater than 0.1. Negligible pressure recovery was shown to exist from the cylindrical periphery of the valve head to the downstream location for all valve lifts, indicating that the flow had probably separated completely from the trailing edge of the valve seating face. The calculated discharge coefficients, based on the geometric throat static pressure measurements on the seating face, were in general less than those determined using the downstream static pressure, by as much as 12% in some instances towards the valves lower mass flow rate range.

Modelling the flow of congestive heart failure patients through a hospital system

The number of hospital admissions in England due to heart failure is projected to increase by over 50% during the next 25 years. This will incur greater pressures on hospital managers to allocate resources in an effective manner. A reliable indicator for measuring the quantity of resources consumed by hospital patients is their length of stay (LOS) in care. This paper proposes modelling the length of time heart failure patients spend in hospital using a special type of Markov model, where the flow of patients through hospital can be thought of as consisting of three stages of care—short-, medium- and longer-term care. If it is assumed that new admissions into the ward are replacements for discharges, such a model may be used to investigate the case-mix of patients in hospital and the expected patient turnover during some specified period of time. An example is illustrated by considering hospital admissions to a Belfast hospital in Northern Ireland, between 2000 and 2004.

Two-phase flow regimes in microchannels

Capillary hydrodynamics has three considerable distinctions from macrosystems: first, there is an increase in the ratio of the surface area of the phases to the volume that they occupy; second, a flow is characterized by small Reynolds numbers at which viscous forces predominate over inertial forces; and third, the microroughness and wettability of the wall of the channel exert a considerable influence on the flow pattern. In view of these differences, the correlations used for tubes with a larger diameter cannot be used to calculate the boundaries of the transitions between different flow regimes in microchannels. In the present review, an analysis of published data on a gas-liquid two-phase flow in capillaries of various shapes is given, which makes it possible to systematize the collected body of information. The specific features of the geometry of a mixer and an inlet section, the hydraulic diameter of a capillary, and the surface tension of a liquid exert the strongest influence on the position of the boundaries of two-phase flow regimes. Under conditions of the constant geometry of the mixer, the best agreement in the position of the boundaries of the transitions between different hydrodynamic regimes in capillaries is observed during the construction of maps of the regimes with the use of the Weber numbers for a gas and a liquid as coordinate axes.

Liquid-Liquid Flow in a Capillary Microreactor: Hydrodynamic Flow Patterns and Extraction Performance

The capillary micro reactor, with four stable operating flow patterns and a throughput range from grams per hour to kilograms per hour, presents an attractive alternative to chip-based and microstructured reactors for laboratory- and pilot-scale applications. In this article, results for the extraction of 2-butanol from toluene under different flow patterns in a water/toluene flow in long capillary microreactors are presented. The effects of the capillary length (0.4-2.2 m), flow rate (0.1-12 mL/min), and aqueous-to-organic volumetric flow ratio (0.25-9) on the slug, bubbly, parallel, and annular flow hydrodynamics were investigated. Weber-number-dependent flow maps were composed for capillary lengths of 0.4 and 2 m that were used to interpret the flow pattern formation in terms of surface tension and inertia forces. When the capillary length was decreased from 2 to 0.4 m, a transition from annular to parallel flow was observed. The capillary length had little influence on slug and bubbly flows. The flow patterns were evaluated in terms of stability, surface-to-volume ratio, throughput, and extraction efficiency. Slug and bubbly flow operations yielded 100% thermodynamic extraction efficiency, and increasing the aqueous-to-organic volumetric ratio to 9 allowed for 99% 2-butanol extraction. The parallel and annular flow operating windows were limited by the capillary length, thus yielding maximum 2-butanol extractions of 30% and 47% for parallel and annular flows, respectively.

Efficiency improvement study for small wind turbines through flow control

In this study, a constant suction technique for controlling boundary layer separation at low Reynolds numbers was designed and tested. This was later implemented on small wind turbines. Small wind turbines need to operate in low wind speeds, that is, in low Reynolds number regimes – typically in the range 104–105. Airfoils are prone to boundary layer separation in these conditions, leading to a substantial drop in aerodynamic performance of the blades. Under these conditions turbines will have reduced energy output. This paper presents experimental results of applying surface-suction over the suction-surface of airfoils for controlling boundary layer separation. The Reynolds numbers for the experiments are kept in the range 8×104–5×105. The air over the surface of the airfoil is drawn into the airfoil through a slit. It is found that the lift coefficient of the airfoils increases and the drag reduces. Based on the improved airfoil characteristics, an analysis of increase in Coefficient of Power (CP), versus input power for a small wind turbine blade with constant suction is presented.

Investigations into the extraction and the determination of polycyclic aromatic hydrocarbons (PAHs) from water by solid-phase extraction and capillary gas chromatography/ mass spectrometry

Factors affecting the detennination of PAHs by capillary GC/MS were studied. The effect of the initial column temperature and the injection solvent on the peak areas and heights of sixteen PAHs, considered as priority pollutants, USillg crosslinked methyl silicone (DB!) and 5% diphenyl, 94% dimethyl, 1% vinyl polysiloxane (DBS) columns was examined. The possibility of using high boiling point alcohols especially butanol, pentanol, cyclopentanol, and hexanol as injection solvents was investigated. Studies were carried out to optimize the initial column temperature for each of the alcohols. It was found that the optimum initial column temperature is dependent on the solvent employed. The peak areas and heights of the PAHs are enhanced when the initial column temperature is 10-20 c above the boiling point of the solvent using DB5 column, and the same or 10 C above the boiling point of the solvent using DB1 column. Comparing the peak signals of the PAHs using the alcohols, p-xylene, n-octane, and nonane as injection solvents, hexanol gave the greatest peak areas and heights of the PAHs particularly the late-eluted peaks. The detection limits were at low pg levels, ranging from 6.0 pg for fluorene t9 83.6 pg for benzo(a)pyrene. The effect of the initial column temperature on the peak shape and the separation efficiency of the PARs was also studied using DB1 and DB5 columns. Fronting or splitting of the peaks was obseIVed at very low initial column temperature. When high initial column temperature was used, tailing of the peaks appeared. Great difference between DB! and.DB5 columns in the range of the initial column temperature in which symmetrical.peaks of PAHs can be obtained is observed. Wider ranges were shown using DB5 column. Resolution of the closely-eluted PAHs was also affected by the initial column temperature depending on the stationary phase employed. In the case of DB5, only the earlyeluted PAHs were affected; whereas, with DB1, all PAHs were affected. An analytical procedure utilizing solid phase extraction with bonded phase silica (C8) cartridges combined with GC/MS was developed to analyze PAHs in water as an alternative method to those based on the extraction with organic solvent. This simple procedure involved passing a 50 ml of spiked water sample through C8 bonded phase silica cartridges at 10 ml/min, dried by passing a gentle flow of nitrogen at 20 ml/min for 30 sec, and eluting the trapped PAHs with 500 Jll of p-xylene at 0.3 ml/min. The recoveries of PAHs were greater than 80%, with less than 10% relative standard deviations of nine determinations. No major contaminants were present that could interfere with the recognition of PAHs. It was also found that these bonded phase silica cartridges can be re-used for the extraction of PAHs from water.

Capillary flow behavior of worm-like micelles studied by small-angle X-ray scattering and small angle light scattering

A novel capillary flow device has been developed and applied to study the orientation of worm-like micelles, among other systems. Small-angle X-ray scattering (SAXS) data from micelles formed by a Pluronic block copolymer in aqueous salt solution provides evidence for the formation of worm-like micelles, which align under flow. A transition from a rod-like form factor to a less persistent conformation is observed under flow. Flow alignment of worm-like micelles formed by the low molar mass amphiphile system cetyl pyridinium chloride+sodium salicylate is studied for comparative purposes. Here, inhomogenous flow at the micron scale is revealed by streaks in the small-angle light scattering pattern perpendicular to the flow direction. Copyright (c) 2006 John Wiley & Sons, Ltd.

Beta-lactoglobulin fibers under capillary flow

We describe the capillary flow behavior of gels of beta-lactoglobulin (beta-lg) containing droplets of fibrils and the shear flow alignment of beta-lg fibers in dilute aqueous solutions. Polarized optical microscopy and laser scanning confocal microscopy are used to show that capillary shear flow does not affect the fibril droplet sizes in the beta-lg gels, the system behaving in this respect as a solution of compact colloidal particles under shear flow. Small-angle X-ray scattering (SAXS) on dilute aqueous solutions indicates that the fibers can be initially aligned under capillary shear, but this alignment is lost after 18 min of shear. Transmission electron microscopy experiments on the samples studied by SAXS suggest that the loss of orientation is due to a shear-induced breakup of the swollen fibril network. Dynamic and static light scattering on dilute beta-lg fibril aqueous solutions are used to show that before shear beta-lg fibrils behave as strongly interacting semiflexible polymers, while they behave as weakly interacting rods after 18 min of capillary shear.