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PubMed1994

Separation of fifteen non-steroidal anti-inflammatory drugs using micellar electrokinetic capillary chromatography.

Micellar electrokinetic capillary chromatography with sodium dodecylsulfate as anionic surfactant was used to separate simultaneously fifteen non-steroidal anti-inflammatory drugs. UV detection was performed at 254 nm. The electroosmotic flow was carefully adjusted for optimal separation. Resolution of the drugs was obtained using a buffer containing 40 mmol l-1 NaH2PO4, 0.104 mol l-1 sodium dodecylsulfate and 3% (v/v) methanol, adjusted to pH 8 with sodium hydroxide. Lack of interference was checked with a number of drugs and metabolites. Between-day coefficients of variation ranged between 2 to 10%.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1994

Capillary zone electrophoresis in polymer networks of polymerase chain reaction-amplified oligonucleotides: the case of congenital adrenal hyperplasia.

The use of capillary zone electrophoresis (CZE) in polymer networks for the analysis of an 8 bp (base pair) deletion in congenital adrenal hyperplasia was investigated. Separations were performed in Tris-borate-EDTA buffer (pH 8.3) containing 6% liquid linear polyacrylamide as a sieving dynamic matrix and 10 microM ethidium bromide for improving DNA fragment separation. Easy analysis and detection of the 127 and 135 bp amplified fragments was accomplished. The capillary column can be used for > 50 analyses before degradation and loss of resolution. The results are comparable to those obtained by gel-slab zone electrophoresis in a 12%T, 4%C polyacrylamide matrix. The sensitivity, by simple UV absorption at 254 nm, is similar to that obtained in gel slabs by dye intercalation staining.

Adrenal Hyperplasia, Congenital↗

PubMed1995

Rapid and sensitive procedure for the separation and quantitation of D- and L-serine in rat brain using gas chromatography-mass spectrometry.

A very simple and rapid GC-MS procedure for the separation and quantitation of D- and L-serine has been developed utilizing a conventional bonded-phase capillary column. The procedure involves initial esterification with isobutanol followed by acylation with the chiral derivatizing reagent S-(-)-N-(heptafluorobutyryl)prolyl chloride (HPC). This procedure requires neither extraction nor clean-up steps and is sensitive to 50 pg on-column. Total time of the procedure is under 3 h and derivatives are stable at room temperature for at least 5 days, making this procedure ideal for automated injections. A simple, one-day synthesis of HPC is described which yields > 99.9% optical purity.

Acylation↗

PubMed1995

Highly sensitive and rapid determination of theophylline, theobromine and caffeine in human plasma and urine by gradient capillary high-performance liquid chromatography-frit-fast atom bombardment mass spectrometry.

A sensitive and reliable analytical procedure has been established for the detection of theophylline (TH), theobromine (TB) and caffeine (CA) in human plasma and urine by gradient capillary high-performance liquid chromatography (HPLC)-frit-fast atom bombardment mass spectrometry (FAB-MS) (LC-frit-FAB-MS). Two capillary columns and a column-switching valve were used in this LC system to allow all of the sample injected to be introduced into the MS system. 7-Ethyltheophylline was used as the internal standard (I.S.). The xanthines in the specimen were extracted with an Extrelut column. The lowest detected amount was ca. 5 ng/ml using this method.

Caffeine↗

PubMed1995

Determination of cimetidine in human plasma by free capillary zone electrophoresis.

The separation of cimetidine from the metabolites cimetidine amide and cimetidine sulfoxide, endogenous creatinine and the internal standard ranitidine was achieved by capillary electrophoresis in less than 5 min. All compounds were well separated from cimetidine, including possible plasma ingredients, as the UV spectra of cimetidine standard and cimetidine from the plasma extract match. Plasma levels of cimetidine were determined in the range 250-3000 ng/ml in plasma and higher concentrations were determined by dilution of the sample with blank plasma.

Capillary Action↗

PubMed1995

Capillary reversed-phase high-performance liquid chromatographic determination of acetyl-methylprednisolone in feline spinal cord.

Capillary reversed-phase high-performance liquid chromatography (RP-HPLC) was used to determine acetylmethylprednisolone (A-MP) that had been administered to feline spinal cord tissue. The method used a 300 mm x 0.32 mm I.D. packed capillary octadecylsilyl (ODS) column and an isocratic mobile phase of 40 mM triethylamine formate (TEAF, pH 3.2)-acetonitrile (50:50, v:v). The chromatographic behavior of A-MP was evaluated with respect to peak-area and peak-height by varying the A-MP concentration (12-190 microM) with a fixed injection volume (1 microliter), and by varying the injection volume (1-10 microliter) with a fixed concentration (12 microM) of A-MP. The limit of detection (signal-to-noise ratio, 3:1) was 250 pg (600 fmol) of synthetic A-MP. Various amounts of A-MP directly spiked into feline spinal cord segments were solvent extracted, separated, and plotted against peak-area (r2 = 1.00). Background tissue without A-MP gives minimal (< 1%) interference at 243 nm. The method also detects exogenous A-MP that was administered into feline spinal cord via an intrathecal injection. Furthermore, the presence of A-MP was confirmed via its molecular ion and corresponding product ions that were obtained by fast-atom bombardment tandem mass spectrometry (FAB-MS-MS).

Animals↗

PubMed1995

Direct gas chromatographic determination of dechloroethylcyclophosphamide following microsomal incubation of cyclophosphamide.

A method for the sensitive determination of dechloroethylcylclophosphamide (3-DCl) in microsomal incubation mixtures was developed. 3-DCl, a side-chain oxidation product of cyclophosphamide (CP), was isolated by extraction with acetic acid ethyl ester following solid-phase extraction on C8 cartridges. Quantification of the metabolite was performed by direct capillary gas chromatography with a nitrogen-phosphorus detector without prior derivatization. The method showed good sensitivity and reproducibility with a detection limit of 1 ng/ml and a limit of quantification of 5 ng/ml. The suitability of the method is shown for the quantification of 3-DCl following incubation of CP with human liver microsomes.

Animals↗

PubMed1994

An MRI study of drying in granular beds of nonporous particles.

MRI is used to study the role of capillary and gravitational forces in controlling mass transport of water during isothermal drying of granular beds of nonporous particles. A new model is presented that shows how capillary and gravitational forces relate to Fickian diffusion driven by a chemical potential gradient. In granular beds, where capillary and gravitational forces dominate, the image profiles give direct information on the dependence of the degree of saturation on capillary suction pressure. The effects of changing particle size and surface tension on the profiles is investigated quantitatively, and it is shown that high capillary pressures create anomalies in the drying profiles.

Algorithms↗

PubMed1994

Water proton relaxation in dilute and unsaturated suspensions of non-porous particles.

NMR water proton relaxation times are reported for suspensions of silica powder of varying silica/water ratios. Pore size distributions and pore connectivities are derived from the relaxation time distributions for the water-saturated suspension. Capillary theory appears to explain the relaxation behaviour of the unsaturated, packed suspensions. The relaxation data in suspensions that have lower solid/liquid ratios than the saturated, packed suspension are sensitive to the particular radial distribution function. This is analysed with a simple cluster model.

Capillary Action↗

PubMed1995

IL-1 beta and TGF-beta 1 modulate the sulphation grade of chondro-disaccharides in porcine articular cartilage: a capillary electrophoresis study.

This report describes the effect of interleukin-1 beta (IL-1 beta) and transforming growth factor-beta 1 (TGF-beta 1) on proteoglycan release from cartilage explants and modification at the sulphation level. Matrix proteoglycans purified by ion-exchange chromatography were composed of two distinct peaks (1 and 2) each showing a different Kav value when they were subjected to size-exclusion chromatography on a Sepharose CL-2B column. Glycosaminoglycans (GAGs) of conditioned medium and extracellular matrix proteoglycans were digested by chondroitin ABC and AC lyase, suggesting that chondroitin sulphate (CS) is the major GAG present (80-90%). Structural analysis of disaccharides, by capillary zone electrophoresis, revealed a different pattern of sulphated glycosaminoglycans when cartilage was treated with either IL-1 beta or TGF-beta 1. Analysis of GAGs released into the medium from TGF-beta 1 treated cartilage showed a reduction in the level of 4-S-disaccharide (delta Di4S) and an increase in non-sulphated disaccharides (delta Di0S), while no significant changes were found in IL-1 beta treated cartilage. In the extracellular matrix, IL-1 beta and TGF-beta 1 induced a more complex rearrangement of the GAGs. The level of non-sulphated disaccharides was increased whereas that of total sulphated disaccharides was reduced. Taken together, these results suggest that both cytokines modify the structure of GAGs, probably by interfering with the activity or the synthesis of sulphotransferases involved in GAG turnover.

Animals↗

PubMed1993

Capillary electrophoresis: pioneering new approaches for biomolecular analysis.

There is little doubt that electrophoretic techniques have made an immeasurable contribution to our understanding of biochemical systems. Capillary electrophoresis (CE), the subject of this article, is not yet as widely utilized as 'slab' gel electrophoresis for the separation of biological molecules, but may confer several advantages over more conventional techniques. For example, it offers fast separation, needs only minute quantities of sample, gives high quantitative reproducibility and can be automated. These qualities make it a highly attractive method, which will ultimately lead to new horizons for biomolecular analyses.

Animals↗

PubMed2003

A mathematical model of lateral flow bioreactions applied to sandwich assays.

Lateral flow (LF) biodetectors facilitate low-cost, rapid identification of various analytes at the point of care. The LF cell consists of a porous membrane containing immobilized ligands at various locations. Through the action of capillary forces, samples and reporter particles are transported to the ligand sites. The LF membrane is then scanned or probed, and the concentration of reporter particles is measured. A mathematical model for sandwich assays is constructed and used to study the performance of the LF device under various operating conditions. The model provides insights into certain experimental observations including the reduction in the level of the detected signal at high target analyte concentrations. Furthermore, the model can be used to test rapidly and inexpensively various operating conditions, assist in the device's design, and optimize the performance of the LF device.

Biosensing Techniques↗

PubMed2004

Analysis of lateral flow biodetectors: competitive format.

Lateral flow (LF) biodetectors facilitate low-cost, rapid identification of various analytes. The LF cell consists of a porous membrane containing immobilized ligands at various locations. Through the action of capillary forces, a mixture of sample and reporter particles is transported to the ligand sites, where the target analytes and the reporters bind to the immobilized ligand. The concentration of the reporters is measured with a scanner. A mathematical model for two different competitive assays is constructed and used to study the performance of LF devices under various operating conditions. The model predicts the signal magnitude as a function of target analyte, reporter, and ligand concentrations, reaction rate constants, and flow rate. The predictions are compared and qualitatively agree with experimental data. The model provides insights into various experimental observations. Furthermore, the model can be used to optimize the performance of LF devices and to inexpensively and rapidly test the system under various operating conditions.

Binding Sites↗

PubMed2004

Dynamic free-surface deformations in axisymmetric liquid bridges.

Thermocapillary convection in a differentially heated liquid bridge is investigated in a two-dimensional numerical study. The deformable free surface is obtained as a solution of the coupled transport equations at fixed unit Prandtl number and aspect ratio. Only steady convection can be realized in this axisymmetric computation with either non-deformable or deformable surfaces. Dynamic free-surface deformations do not induce transitions to oscillatory convection even at large Reynolds numbers. Free surfaces are convex near the cold wall due to large surface pressures at the stagnation-point. Near the hot wall they change from concave to convex with increasing Re due to large normal viscous stresses. Large Capillary numbers cause additional surface ripples there while having little effect on the interior. Heat loss from the free surface has dramatic influence on the dynamics and must be included in theoretical models of thermocapillary instabilities.

Capillary Action↗

PubMed2004

A microbead array chemical sensor using capillary-based sample introduction: toward the development of an "electronic tongue".

The development of a micromachined fluidic structure for the introduction of liquid samples into a chip-based sensor array composed of individually addressable polymeric microbeads is presented. The micromachined structure consists of micromachined storage cavities combined with a covering glass layer that confines the microbeads and fluidic channels. In our sensor array transduction occurs via optical (colorimetric and fluorescence) changes to receptors and indicator molecules that are covalently attached to termination sites on the polymeric microbeads. Spectral data are acquired for each of the individual microbeads using a charged-coupled device (CCD) allowing for the near-real-time analysis of liquid sample. Hence the micromachined fluidic structure must allow for both optical access to the microbeads and fluid flow through the micromachined cavities that serve as the microreactors/analysis chambers. One of the key parts of the structure is a passive fluid introduction system driven only by capillary force. This simple means of fluid introduction realizes a compact device. The capillary flow on the inlet channel has been studied, and the responses of the microbeads (alizarin complexone) to a liquid sample have been characterized. The test results show that this system is useful in a micro-total-analysis-system (mu-TAS) and biomedical applications.

Biomimetics↗

PubMed2005

Optical microsensors for pesticides identification based on porous silicon technology.

A simple and low cost optical sensor, based on porous silicon nanotechnology, has been used to detect and quantify the presence of atrazine pesticide in water and humic acid solutions. In both cases, a well defined optical signal variation can be registered, even at low concentration as 1 ppm. The phenomenon can be ascribed to the capillary infiltration of liquid into the pores, which changes the average refractive index of the structure. Due to the resonant cavity enhanced operation of the proposed sensors, very low detection limits can be reached.

Atrazine↗

PubMed2004

Flow and injection characteristics of pharmaceutical parenteral formulations using a micro-capillary rheometer.

A micro-capillary rheometer consisted of a fine needle with an internal diameter of 347 microm attached to a 1 ml removable-needle syringe within an Instron device that operated in compression mode to provide various crosshead speeds ranging from 150 to 950 mm min(-1) covering typical clinical injection rates, and that determined the resulting force on the plunger. The crosshead speed and the resulting force were used to calculate the shear rate and the shear stress respectively. These were used in standard capillary flow expressions together with an independent measurement of the wall frictional force and allowed the viscosity of parenteral Newtonian solutions and non-Newtonian suspensions to be measured quantitatively and their rheological behaviour in needles of clinical dimensions to be established. Commercial pharmaceutical parenteral formulations consisting of three oil-based solutions and three aqueous suspensions were chosen for this study. The net injection forces were also obtained and it was shown that both the oil-based solutions and the aqueous suspensions covered similar ranges. The viscosities for the parenteral solutions were determined from the slope of the linear regression (R(2)>0.97) between shear stress and shear rate and ranged between 0.029 and 0.060 Pas. For the aqueous suspensions examined, viscosities decreased from low shear rate to high shear rate, following a power-law model and indicating a pseudo plastic behaviour. Standardisation of the micro-capillary rheometer with Newtonian silicone oils calibrated with a Rheometrics Fluids Spectrometer showed viscosity values consistent between the rotational flow measurements and capillary flow measurements which were within 5% and showed very high degrees of reproducibility between replicate samples. This degree of reproducibility allowed differences in the contribution of the wall frictional force to the required plunger force for both the oil-based and aqueous parenteral formulations to be determined reliably. The wall frictional force values for all formulations were similar (0.6-1.6 N) but the frictional forces of aqueous systems were found to decline significantly with plunger speed. The micro-capillary rheometer has been used to evaluate the impact of concentration changes due to sedimentation on the injectability of one of the aqueous suspensions, where it was shown that not only the viscosity increased but the shear thinning behaviour ceased at higher shear rates. The micro-capillary rheometer which was able to operate in clinical shear rate ranges has been shown to detect deteriorations in the injectable rheology of suspensions, which in the case here was due to pre-injection sedimentation.

Capillary Action↗

PubMed2005

Leveling response factors in the electrospray ionization process using a heated capillary interface.

Several investigators have observed a discrepancy in electrospray response of complementary strands from denatured DNA, which has been attributed to the difference in hydrophobicity between the two strands; the more hydrophobic species tend to have higher ion abundances. The implementation of a heated electrospray source has allowed us to "level" the electrospray response for two equimolar complementary strands with different hydrophobicities. As the temperature was increased, the ratio of ion abundances of the less hydrophobic noncoding strand to the more hydrophobic coding strand approached unity. Furthermore, the heated electrospray source was used to denature amplicons containing 7-deaza purines, which can be used to facilitate sequencing by mass spectrometry.

Capillary Action↗