Biomedical subjects

Elwin X Vrouwe

Publications and source records attributed to Elwin X Vrouwe.

4 recordsLinked to original sources

PubMed2006

Microchip capillary electrophoresis for point-of-care analysis of lithium.

BACKGROUND: Microchip capillary electrophoresis (CE) is a promising method for chemical analysis of complex samples such as whole blood. We evaluated the method for point-of-care testing of lithium. METHODS: Chemical separation was performed on standard glass microchip CE devices with a conductivity detector as described in previous work. Here we demonstrate a new sample-to-chip interface. Initially, we took a glass capillary as a sample collector for whole blood from a finger stick. In addition, we designed a novel disposable sample collector and tested it against the clinical standard at the hospital (Medisch Spectrum Twente). Both types of collectors require < 10 microL of test fluid. The collectors contain an integrated filter membrane, which prevents the transfer of blood cells into the microchip. The combination of such a sample collector with microchip CE allows point-of-care measurements without the need for off-chip sample treatment. This new on-chip protocol was verified against routine lithium testing of 5 patients in the hospital. RESULTS: Sodium, lithium, magnesium, and calcium were separated in < 20 s. The detection limit for lithium was 0.15 mmol/L. CONCLUSIONS: The new microchip CE system provides a convenient and rapid method for point-of-care testing of electrolytes in serum and whole blood.

Antimanic Agents↗

PubMed2005

Rapid inorganic ion analysis using quantitative microchip capillary electrophoresis.

Rapid quantitative microchip capillary electrophoresis (CE) for online monitoring of drinking water enabling inorganic ion separation in less than 15 s is presented. Comparing cationic and anionic standards at different concentrations the analysis of cationic species resulted in non-linear calibration curves. We interpret this effect as a variation in the volume of the injected sample plug caused by changes of the electroosmotic flow (EOF) due to the strong interaction of bivalent cations with the glass surface. This explanation is supported by the observation of severe peak tailing. Conducting microchip CE analysis in a glass microchannel, optimized conditions are received for the cationic species K+, Na+, Ca2+, Mg2+ using a background electrolyte consisting of 30 mmol/L histidine and 2-(N-morpholino)ethanesulfonic acid, containing 0.5 mmol/L potassium chloride to reduce surface interaction and 4 mmol/L tartaric acid as a complexing agent resulting in a pH-value of 5.8. Applying reversed EOF co-migration for the anionic species Cl-, SO42- and HCO3- optimized separation occurs in a background electrolyte consisting of 10 mmol/L 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and 10 mmol/L HEPES sodium salt, containing 0.05 mmol/L CTAB (cetyltrimethylammonium bromide) resulting in a pH-value of 7.5. The detection limits are 20 micromol/L for the monovalent cationic and anionic species and 10 micromol/L for the divalent species. These values make the method very suitable for many applications including the analysis of abundant ions in tap water as demonstrated in this paper.

Electrophoresis, Microchip↗

PubMed2005

Microchip analysis of lithium in blood using moving boundary electrophoresis and zone electrophoresis.

The determination of inorganic cations in blood plasma is demonstrated using a combination of moving boundary electrophoresis (MBE) and zone electrophoresis. The sample loading performed under MBE conditions is studied with the focus on the quantitative analysis of lithium. A concentration adjustment takes place when the sample components migrate into the chip during the sample loading step. Using a heart-cutting method, a diluted sample plug is subsequently separated with capillary zone electrophoresis. The excessive dispersion that is typical of the samples with a high ionic strength is thereby prevented. The method can be easily applied to commercially available capillary electrophoresis microchips under the condition that the electroosmotic flow is suppressed. For the first time the lithium concentration is determined in the blood plasma from a patient on lithium therapy without sample pretreatment. Using a microchip with conductivity detection, a detection limit of 0.1 mmol/L is obtained for lithium in a 140 mmol/L sodium matrix.

Electric Conductivity↗

PubMed2004

Direct measurement of lithium in whole blood using microchip capillary electrophoresis with integrated conductivity detection.

The direct measurement of lithium in whole blood is described. Using microchip capillary electrophoresis (CE) with defined sample loading and applying the principles of column coupling, alkali metals were determined in a drop of whole blood. Blood collected from a finger stick was mixed with anticoagulant and transferred onto the chip without extraction or removal of components. The electrokinetic transport of red blood cells inside the channels was studied to find sample loading conditions suitable for the analysis of lithium without injecting cells into the separation channel. Both bare glass chips and chips coated with polyacrylamide were used showing the behavior of the cells under different electroosmotic flow conditions. In serum a detection limit for lithium of 0.4 mmol/L was reached. Proteins quickly contaminated untreated chip surfaces but devices with coating gave reproducible electropherograms. In addition, potassium and sodium were also detected in the same separation run. To our knowledge, this is the first device to directly measure ions in whole blood with the use of capillary zone electrophoresis on a microchip.

Acrylic Resins↗