Multicapillary System Research Articles

Exact analytical expressions for the band broadening in polydisperse 2-D multi-capillary columns with diffusional bridging

Using a recent generalization of the Aris dispersion method, we have derived exact analytical expressions for the long-time limit dispersion in 2-D multi-capillary packings with diffusional bridging (binary channel system). Both the plug flow and the parabolic flow case are considered. The expressions are mathematically exact over the entire range of possible values of the degree of polydispersity (σ), the retention equilibrium constant K and the diffusion coefficients in the mobile and stationary zone. They are validated by comparing them to the dispersion data obtained by numerically solving the partial differential equation describing the general advection-diffusion mass balance. A correlation coefficient of R2 > 0.99995 is obtained. The form of the obtained analytical expression shows the dispersion arising from the polydispersity effect in multi-capillary systems can be split in two contributions, one related to the actual velocity difference between the adjacent channels and one related to the fact that the average of the intra-capillary C-term band broadening is larger in any σ≠0-case than in the σ=0-case. When leaving the small σ-assumption, a new factor ((1- σ2)/(1+3σ2)2) emerges, common to both the solution for the plug flow and the parabolic case. The analysis shows the parabolic flow not only leads to a larger intra-capillary dispersion (σ=0) than the plug flow case as known from literature but is also more sensitive to the polydispersity effect (up to some 10 to 20%).

Dynamic characteristics of charged droplets in an electrostatic spraying process with twin capillaries

Abstract The experimental and simulated investigations on electrostatic spraying with twin capillaries are carried out. The starting electric voltage required for the cone-jet and the deposition characteristics of the droplets are measured. The whole spraying process, which includes jet and droplet motions, is simulated and the simulated results on the motions of jet and droplet are basically consistent with the experiments. According to the simulated results, the contributions of various electric forces to droplet movement are quantitatively analyzed and the droplet dynamic characteristics, especially the interaction mechanism between two sprays, are revealed. The test results on the droplet deposition characteristics partially support the simulated results on the droplet motion. The present work is useful for a better understanding on the interaction between sprays in double or multi-capillary system.

From 'Lab & Light on a Chip' to Parallel Microflow Photochemistry

Continuous-flow microreactors offer major advantages for photochemical applications. This mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry. Whereas the enclosed microchip offered high space–time-yields, the open capillary-type reactor showed a greater potential for further modifications. Consequently, a 10-microcapillary reactor was constructed and used successfully for process optimization, reproducibility studies, scale-up, and library synthesis. To demonstrate the superiority of microflow photochemistry over conventional batch processes, the reactors were systematically evaluated using alcohol additions to furanones as model reactions. In all cases, the microreactor systems furnished faster conversions, improved product qualities, and higher yields. UVC-induced [2+2] cycloadditions of furanone with alkenes were exemplarily examined in a capillary reactor, thus proving the broad applicability of this reactor type.

Application of short‐end injection procedure in CE

CE is well known for its many advantages, including the speed of the analyses; most of which can be accomplished in less than 10 min. However many potential fields of application such as pharmaceutical research and industry and clinical diagnostics require analyses of large numbers of samples and so need an even shorter analysis time to be practical. There are generally three main options for enhancing the throughput of electromigration methods - using microchip or multi-capillary systems or modifying the method preformed on single capillary instruments. The latter option will probably be the method of choice for most laboratories, since they are only equipped with classical commercial CE instrumentation. Although several approaches can be used - higher electric field, EOF modification, external pressure application during analysis, this article reviews one of the simplest and at the same time most used, the so-called short-end injection procedure.

Re-assessment of the cut-off levels of Carbohydrate Deficient Transferrin (CDT) for automated immunoassay and multi-capillary electrophoresis for application in a forensic context

BackgroundThe determination of Carbohydrate Deficient Transferrin (CDT) in a forensic context should be based on the use of a screening technique followed, for the “positive samples”, by a confirmatory technique. The aim of this study was to compare the two most used automated screening methods for CDT analysis, immuno-nephelometric assay (INA) and multi-capillary electrophoresis (mCE), with a validated HPLC procedure, used as confirmation test, in order to re-evaluate the cut-off concentrations of the screening methods. Methods195 serum samples underwent CDT analysis by using the N Latex CDT direct immuno-nephelometric assay, the multicapillary system Capillarys™ and an anion exchange HPLC method with UV-visible detection at 460nm developed and validated at our laboratories. Statistical analyses were performed by using Bland–Altman plots and ROC curves. Results and discussionThe 95% limits of agreement were ±0.94% when comparing INA and HPLC and ±0.60% when comparing mCE and HPLC. The ROC analysis of both INA and mCE, using HPLC as the reference method, showed that no false negative results were found when the cut-off was fixed to 1.2% for mCE and to 2.3% for INA. ConclusionsThe study showed a good agreement among CDT determinations carried out either with mCE or INA or HPLC. However, the usual cut-offs of both mCE (1.3%) and INA (2.5%) should be lowered to minimize false negatives at the screening analysis.

Evaluation of capillary electrophoresis assay for CDT on SEBIA's Capillarys System: Intra and inter laboratory precision, reference interval and cut-off

Background Carbohydrate-deficient transferrin (CDT) measurement on the multicapillary system Capillarys™ is characterized by high throughput and an on-line sample pre-treatment. This study evaluates the linearity and the precision of this technique, the correlation with the candidate reference method and the effect of genetic transferrin variants. Upper reference limit and cut-off values were calculated. Methods The precision study was carried out following CLSI EP5-A protocol. The between laboratory variation was calculated from an eight-site study. The upper reference limit (URL) was conventionally calculated from a reference population of 225 samples and verified by a Bhattacharya analysis in a large (n = 19,129) population. A population of 314 heavy consumers was used for calculation of the cut-off limit. Additionally the measurement uncertainty was calculated according to EDMA (European Diagnostic Manufacturers Association) and IRMM. Results The imprecision found was less than 5%, linearity was excellent for CDT values ranging from 2% to 20%. The between site variation around the cut-off value (CDT ranging from 1.68% to 1.79%) was clinically not significant. The upper reference limit (95th percentile) was calculated at 1.3% by the conventional IFCC method and confirmed by Bhattacharya calculations. The optimum cut-off for this CZE method was 1.6%, taken into account the measurement uncertainty. The regression equation with the candidate reference method was Disialotransferrin(Capillarys2) = Disialotransferrin(HPLC) ∗ 0.968 − 0.248. Genetic variants and abnormal profiles were well recognized. Conclusions These results demonstrate that the Capillarys CDT method is robust and reliable in routine use with a high degree of homogeneity from one system to another and is highly correlated with the candidate HPLC reference method.

Fully automated analysis of Carbohydrate-Deficient Transferrin (CDT) by using a multicapillary electrophoresis system

Background The techniques universally believed as most reliable for determination of Carbohydrate-Deficient Transferrin (CDT) are HPLC and capillary electrophoresis (CE). Recently a reagent kit for CDT analysis to be used in a multicapillary electropherograph has been introduced. The present work was aimed at a validation of this new commercial system by application of the analytical chemistry parameters and by comparison with validated CE and HPLC methods. Methods One hundred forty serum samples were analyzed with multicapillary CE (Capillarys™, Sebia, France) using kit reagents (CAPILLARYS™ CDT assay), with single capillary electropherograph (P/ACE MDQ, Beckman Coulter, USA) using an original method developed by our group and with HPLC, performed on a gradient HPLC (Shimadzu Europe, Germany), using column and reagents provided in kit (ClinRep®, Recipe, Germany). Results The separation efficiency of the multicapillary system was about 15,000 theoretical plates/column. The resolution of the transferrin isoforms ranged from 1.23 to 1.67. The variation coefficient was < 10% in both intra-run and between run tests. The correlation of results of multicapillary CE with those obtained with single CE and HPLC was statistically significant. Conclusions The multicapillary system shows high productivity with good analytical performances; however, a confirmation of positive results with an alternative method is required.

Capillaries within compartments: microvascular interpretation of dynamic positron emission tomography data

Measurement of exchange of substances between blood and tissue has been a long-lasting challenge to physiologists, and considerable theoretical and experimental accomplishments were achieved before the development of the positron emission tomography (PET). Today, when modeling data from modern PET scanners, little use is made of earlier microvascular research in the compartmental models, which have become the standard model by which the vast majority of dynamic PET data are analysed. However, modern PET scanners provide data with a sufficient temporal resolution and good counting statistics to allow estimation of parameters in models with more physiological realism. We explore the standard compartmental model and find that incorporation of blood flow leads to paradoxes, such as kinetic rate constants being time-dependent, and tracers being cleared from a capillary faster than they can be supplied by blood flow. The inability of the standard model to incorporate blood flow consequently raises a need for models that include more physiology, and we develop microvascular models which remove the inconsistencies. The microvascular models can be regarded as a revision of the input function. Whereas the standard model uses the organ inlet concentration as the concentration throughout the vascular compartment, we consider models that make use of spatial averaging of the concentrations in the capillary volume, which is what the PET scanner actually registers. The microvascular models are developed for both single- and multi-capillary systems and include effects of non-exchanging vessels. They are suitable for analysing dynamic PET data from any capillary bed using either intravascular or diffusible tracers, in terms of physiological parameters which include regional blood flow.

Capillary electrophoresis with laser-induced fluorescence in clinical drug development: Routine application and future aspects

The clinical bioanalytical setting is characterized by sample volumes of <1 ml biological fluid (e.g. plasma, urine), a range of 3–4 decades of concentrations to be quantified and a limit of quantitation in the μg/l–ng/l range for sets of 100–5000 individual samples. Setup of capillary electrophoresis (CE) for routine application in this analytical field was successful for analytes accessible to fluorescence detection by using laser-induced fluorescence (LIF) detection. Empowerment of CE–LIF for routine serial analysis of thousands of samples includes improvement in autosampler techniques, thorough procedures for capillary treatment and particularly more advanced detection technology. Introduction of multi-capillary systems with charge-coupled device cameras and frequency doubled Ar-ion laser ( λ=257 nm) offers this technique the chance of superiority over classical analytical assays — especially in the field of (new) low volume samples e.g. capillary blood or microdialysate encouraging clinicians to search for meaningful non-invasive samples.

Combination of Fractal Geometry and Hydrodynamics: A Novel Approach to the Study of a Multicapillary Electrophoresis System

In this paper, the effect of the capillary structure and its organization in a multicapillary electrophoresis system (MES) were studied. The model was based on a combination of the dynamics of energy transport and the mathematics of fractal geometry. It demonstrated that in order to minimize the energy transport the geometric system structure must obey certain power laws. The results obtained showed that these power laws depend on the hydrodynamic regime and the capillary material. For polymeric capillaries in a pulsed flow, the viscous resistance in the fractal multicapillary system (FMS) varied with 1/r2 for the smallest capillaries (r was the dimension of the capillary cross-section) and with 1/r4 (Poiseuille flow regime) for the largest capillaries. For a constant flow, the Poiseuille regime was always respected. The FMS can use high field strengths without too much energy dissipation to perform rapid and efficient separation.

A molecular beam detector to determine the specific outgassing rate of small specimens

A molecular beam detector was designed to measure the specific outgassing rate of metal samples in the UHV region at reduced influence of the gas desorbed from the walls of the chamber. The detector consists of a nude Bayard-Alpert gauge surrounded by a liquid nitrogen cooled stainless steel tube. The orifice in direction to the sample was designed as a multicapillary system (MCS) containing 85 capillaries of 1 mm diameter. Molecules desorbed from the sample can reach the interior of the detector directional resolved by the MCS and can be detected. A shutter between the MCS and the sample is used for the determination of the background of the equipment. The derivation of the formulae for the determination of the specific outgassing rates from the pressure measured in the detector chamber is explained. First experimental results are discussed.

Analysis of capillary-tissue diffusion in multicapillary systems

The diffusive transport of a substance between a parallel capillary network and the surrounding tissue is investigated. The consumption/production rate of the substance in the tissue is assumed to be constant (zero-order chemical kinetics). The solution of the diffusion problem which describes the distribution of the substance in the tissue and along the capillary network is found in an analytical form. A rather general assumption regarding the symmetry of capillary network makes it possible to formulate a Neumann-type boundary-value problem in a rectangular domain. The solution of the diffusion problem in the rectangle allows the capillary-tissue fluxes to be expressed linearly in terms of the concentrations in the capillaries, and hence leads to ordinary differential equations for those concentrations. Several examples are considered with different network geometry and concurrent or countercurrent flow conditions. The solution makes it possible to investigate the effect of capillary interaction on mass transfer in various microcirculatory units.

Gill function in an elasmobranch

Highly efficient oxygen uptake in elasmobranchs, as indicated by frequent excess of PaO2 over PEO2 has previously been ascribed to the operation of multicapillary rather than counter-current gas exchange by the gills. Analysis of models shows that, at maximum efficiency, a multicapillary system cannot account for values of PaO2 greater than (PIO2+PEO2)/2. In Port Jackson sharks Heterodontus portusjacksoni) PaO2 commonly exceeds (PIO2+PEO2)/2, which indicates the operation of a functional counter-current at the respiratory surface. The anatomical basis of this counter-current is provided by the demonstration that a continuous flow of water passes between the secondary lamellae into septal canals and thence via the parabranchial cavities to the exterior.