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Measuring Cell (measuring + cell)
Selected AbstractsApplication of Exchangeable Biochemical Reactors with Oxidase-Catalase-Co-immobilizates and Immobilized Microorganisms in a Microfluidic Chip-CalorimeterENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008M. Leifheit Abstract Several methods for the quantitative detection of different compounds, e.g., L -amino acids, sugars or alcohols in liquid media were developed by application of an automatic measuring unit including a fluid chip-calorimeter FCC-21. For this purpose, enzymes were immobilized covalently on the inner and outer surface of CPG (controlled porous glass)-spherules with an outer diameter of 100,,m and filled into a micro flow-through reaction chamber (VR = 20,,L). The design of the measuring cell allows for easy insertion into the calorimeter device of a stored series of comfortably pre-fabricated measuring cells. These cells can be filled with different enzyme immobilizates. Different oxidases were used and co-immobilized with catalase for the improvement of the detection sensitivity. A signal amplification could be achieved up to a factor of 3.5 with this configuration. ,- D -glucose, ethanol and L -lysine could be detected in a range of 0.25,1.75,mM using glucose oxidase, alcohol oxidase and lysine oxidase. The group of oxidases in combination with the enzymatic catalysis of the intermediate H2O2 allows the quantitative detection of a large number of analytes. A good measurement and storage stability could be achieved for several weeks by this immobilization method. In addition to enzyme-based detection reactions, it was shown that living microorganisms can be immobilized in the reaction chamber. Thus, the system can be used as a whole-cell biosensor. The quantitative detection of phenol in the range of 10,100,,M could be performed using the actinomycete Rhodococcus sp. immobilized on glass beads by means of embedding into polymers. [source] Eignung eines großen Flüssigkeits- und eines Luftpyknometers zur Bestimmung des Rohvolumens von Feststoffen unterschiedlicher Art und GrößeJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2005Berthold Deller Abstract Das Feststoffvolumen von Materialien, die sowohl relativ große als auch spezifisch leichte Bestandteile enthalten, kann nach DIN ISO 11508 (mit relativ kleinen Flüssigkeitspyknometern (FP) und submerser Wägung in Wasser) nicht bestimmt werden. Deshalb wurde geprüft, ob es ohne Zerkleinerung des Untersuchungsmaterials in einem größeren FP (ca. 280,cm3) oder einem Luftpyknometer (LP) genau genug zu ermitteln ist. Materialien mit gröberen Bestandteilen bzw. Feststoffe mit sehr unterschiedlicher Rohdichte ergaben mit dem FP größere Differenzen zwischen Parallelansätzen als die wiederholte Befüllung mit Wasser und die Untersuchung von feinkörnigen Mineralböden erwarten ließ. Die wesentliche Ursache dafür wird in der materialspezifischen Inhomogenität gesehen. Das FP scheint somit für die Untersuchung von Materialien mit Partikeldurchmessern von bis zu 3,cm grundsätzlich geeignet. Die Bestimmung muss jedoch jeweils an mindestens zwei Parallelproben erfolgen und ggf. erweitert werden, um verlässliche Mittelwerte zu erhalten. Die gleiche Bestimmung mit einem selbst gebauten LP ergab zu niedrige Werte für das Rohvolumen, wenn die Materialien ofentrocken, lufttrocken und feucht waren (Ausnahme: solche mit kompakten und relativ großen Partikeln). Die Fehler traten sowohl bei der Messung durch Luftdrucksenkung (ca. ,300 hPa) als auch unter Druckerhöhung (ca. 100,hPa) auf. Das Volumen von reinem Wasser konnte demgegenüber unter Druckerhöhung wesentlich genauer und richtiger bestimmt werden. Nach Kochen der Proben (wie für die Flüssigkeitspyknometrie) und Überdecken mit Wasser in der LP-Messkammer waren die Ergebnisse deutlich besser mit denen des FP vergleichbar und plausibler. Die Fehlerursachen werden darin gesehen, dass die Messung durch adsorbierte Luft (getrocknete und lufttrockene Proben) gestört wird bzw. Wasser von den Materialoberflächen während des Messvorganges verdampft. Suitability of a large liquid pycnometer and an air pycnometer to determine the raw volume of solids of different type and size The raw volume of materials, which contain constituents of relatively large size as well as of low density, can not be determined according to ISO 11508 without grinding. Therefore, this study should show if the analysis can be performed on original-sized materials with a large liquid pycnometer (LP, volume of about 280,cm3) or a self-made air pycnometer (AP). When materials of particle size up to 16,mm and/or of very different raw density were analyzed with the LP, the differences between parallel measurements were considerably greater than those of fine-textured soils and than those expected from repeated filling of the LP with water. They are ascribed mainly to the inhomogeneity of the samples and less to measuring errors. Consequently, the LP used seems to be suitable for the determination of particles with constituent size of up to 3,cm. However, the volume determination of every sample has to be performed at least twice. If the results do not meet the required precision, more repetitious measurements have to be performed, or the sample amount has to be enlarged. The same determination with the AP led to comparable and plausible results only in the case of water and of materials with compact constituents of relatively great size mainly (sand and fine gravel), when the samples were oven-dry, air-dry, or fairly moist. The results of the other materials were comparable, when the same sample preparation was performed as with liquid pycnometry (heating-up in water) and when they were covered by water in the measuring cell during measurement. The deviations from LP measurements were reduced, when measuring was performed by increasing air-pressure conditions (100 hPa) instead of lowering (,300 hPa), but to an insufficient degree. The reason for erroneous results was attributed to the existence of adsorbed air on particle surfaces (dry materials) and the evaporation of water during the measuring step (moist samples), respectively. [source] Dielectrophoresis microsystem with integrated flow cytometers for on-line monitoring of sorting efficiencyELECTROPHORESIS, Issue 24 2006Zhenyu Wang Abstract Dielectrophoresis (DEP) and flow cytometry are powerful technologies and widely applied in microfluidic systems for handling and measuring cells and particles. Here, we present a novel microchip with a DEP selective filter integrated with two microchip flow cytometers (FCs) for on-line monitoring of cell sorting processes. On the microchip, the DEP filter is integrated in a microfluidic channel network to sort yeast cells by positive DEP. The two FCs detection windows are set upstream and downstream of the DEP filter. When a cell passes through the detection windows, the light scattered by the cell is measured by integrated polymer optical elements (waveguide, lens, and fiber coupler). By comparing the cell counting rates measured by the two FCs, the collection efficiency of the DEP filter can be determined. The chips were used for quantitative determination of the effect of flow rate, applied voltage, conductivity of the sample, and frequency of the electric field on the sorting efficiency. A theoretical model for the capture efficiency was developed and a reasonable agreement with the experimental results observed. Viable and non-viable yeast cells showed different frequency dependencies and were sorted with high efficiency. At 2,MHz, more than 90% of the viable and less than 10% of the non-viable cells were captured on the DEP filter. The presented approach provides quantitative real-time data for sorting a large number of cells and will allow optimization of the conditions for, e.g., collecting cancer cells on a DEP filter while normal cells pass through the system. Furthermore, the microstructure is simple to fabricate and can easily be integrated with other microstructures for lab-on-a-chip applications. [source] Application of Exchangeable Biochemical Reactors with Oxidase-Catalase-Co-immobilizates and Immobilized Microorganisms in a Microfluidic Chip-CalorimeterENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008M. Leifheit Abstract Several methods for the quantitative detection of different compounds, e.g., L -amino acids, sugars or alcohols in liquid media were developed by application of an automatic measuring unit including a fluid chip-calorimeter FCC-21. For this purpose, enzymes were immobilized covalently on the inner and outer surface of CPG (controlled porous glass)-spherules with an outer diameter of 100,,m and filled into a micro flow-through reaction chamber (VR = 20,,L). The design of the measuring cell allows for easy insertion into the calorimeter device of a stored series of comfortably pre-fabricated measuring cells. These cells can be filled with different enzyme immobilizates. Different oxidases were used and co-immobilized with catalase for the improvement of the detection sensitivity. A signal amplification could be achieved up to a factor of 3.5 with this configuration. ,- D -glucose, ethanol and L -lysine could be detected in a range of 0.25,1.75,mM using glucose oxidase, alcohol oxidase and lysine oxidase. The group of oxidases in combination with the enzymatic catalysis of the intermediate H2O2 allows the quantitative detection of a large number of analytes. A good measurement and storage stability could be achieved for several weeks by this immobilization method. In addition to enzyme-based detection reactions, it was shown that living microorganisms can be immobilized in the reaction chamber. Thus, the system can be used as a whole-cell biosensor. The quantitative detection of phenol in the range of 10,100,,M could be performed using the actinomycete Rhodococcus sp. immobilized on glass beads by means of embedding into polymers. [source] | ||||||||||