Abstract: Microchip devices and methods of use are provided for the controlled exposure of a secondary device. In one embodiment, the microchip device include a substrate, a plurality of reservoirs in the substrate, a secondary device in one or more of the reservoirs, at least one barrier layer covering each of the reservoirs to isolate the secondary device from an environmental component outside the reservoirs, wherein the barrier layer is impermeable to the environmental component, and a microprocessor-controlled actuation means for rendering the barrier layer porous or permeable to the environmental component to expose the secondary device to said environmental component. The secondary device can comprise a sensor or sensing component (e.g., a biosensor). In other embodiments, microchip devices are provided for the controlled exposure of a reacting component, such as an enzyme. In still other embodiments, sensors are provided on the device outside of the reservoirs.

Abstract: Microchip devices are provided which include a substrate having a plurality of reservoirs containing a secondary device, a reacting component, or a combination thereof. At least one barrier layer covers each reservoir to isolate the reservoir contents from one or more environmental components outside the reservoirs. The barrier layer can be selectively disintegrated or permeabilized to expose the isolated contents to the one or more environmental components. The secondary device preferably includes a sensor or sensing component, for example, a biosensor, or a light detection or imaging device, such as an optical fiber. Preferred reacting components include catalysts and reagent, which may be immobilized in the reservoirs.

Abstract: Microchip devices are provided which include a substrate having a plurality of reservoirs containing a secondary device, a reacting component, or a combination thereof. At least one barrier layer covers each reservoir to isolate the reservoir contents from one or more environmental components outside the reservoirs. The barrier layer can be selectively disintegrated or permeabilized to expose the isolated contents to the one or more environmental components. The secondary device preferably includes a sensor or sensing component, for example, a biosensor, or a light detection or imaging device, such as an optical fiber. Preferred reacting components include catalysts and reagent, which may be immobilized in the reservoirs.

Abstract: An electrochemical sensor for detecting the presence and amount of acetate in cell culture and fermentation media. The electrochemical sensor has a pH electrode, an internal reference electrode, a special high-tensile strength gas permeable membrane, and internal reference electrolyte such that acetate concentration can be measured using a pretreatment buffer having a pH of about 5.5.

Abstract: A disposable electrode strip for testing a fluid sample including a laminated strip with a first and second end, a reference electrode embedded in the laminated strip proximate to the first end, at least two working electrodes embedded in the laminated strip proximate to the first end and the reference electrode, an open path for receiving a fluid sample beginning from the first end and being sufficiently long to expose the reference electrode and the working electrodes to the fluid sample, and conductive contacts located at the second end of the laminated strip. The laminated strip has a base layer with a conductive coating, a reagent holding layer, a channel forming layer and a cover. One of the working electrodes contains a reagent substantially similar to the reagent of the reference electrode and a second working electrode contains a reagent having an enzyme.

Abstract: A disposable electrode strip for testing a fluid sample including a laminated strip with a first and second end, a vent, an open path for receiving a fluid sample of less than one microliter beginning from the first end and connecting to the vent, a working electrode, a reference electrode and a pseudo-working electrode embedded in the laminated strip within the open path and proximate to the first end, a reagent matrix coextensive within the open path and covering the three electrodes, and conductive contacts located at the second end of the laminated strip.

Abstract: An electrochemical sensor with a gelled membrane for prolonging the useful life of an ion-selective electrode. The gelled membrane is a hydrophilic membrane having a specially-formulated gel layer coated on one side. The gel-coated side of the gelled membrane is in intimate contact with the ion-selective membrane and separates the ion-selective membrane from the test samples and the calibration and cleaning fluids. The gelled membrane is a semi-permeable barrier which allows passage of the species to be measured while inhibiting the passage of surfactant and proteinaceous material into the polymeric ion-selective membrane.

Abstract: Disclosed is a method of assaying a high concentration of a substance in a liquid sample with a polarographic cell. The cell contains an electrode assembly that includes a reference electrode and a hydrogen peroxide sensor electrode having a laminated membrane covering the liquid sample contacting face of the sensor electrode. The laminated membrane includes an outer membrane permeable to the substance and oxygen, an inner membrane permeable to hydrogen peroxide and located adjacent the face of the sensor electrode, and an enzyme layer between the inner and outer membrane; the enzyme in the enzyme layer can oxidize the substance to generate hydrogen peroxide.

Abstract: The present invention concerns sodium silicate and sodium aluminosilicate glass compositions which contain specified proportions of tantalum oxide and glass electrodes made thereform, which are particularly sensitive to sodium ions in aqueous solutions containing sodium ions and other monovalent cations. These glasses represent an improvement over sodium aluminosilicate glass electrodes of the type disclosed in U.S. Pat. No. 2,829,090.

Abstract: The present invention concerns sodium silicate and sodium aluminosilicate glass compositions which contain specified proportions of tantalum oxide and glass electrodes made therefrom, which are particularly sensitive to sodium ions in aqueous solutions containing sodium ions and other monovalent cations. These glasses represent an improvement over sodium aluminosilicate glass electrodes of the type disclosed in U.S. Pat. No. 2,829,090.

Abstract: Disclosed are pH responsive glass compositions which contain specified proportions of LiO.sub.2, SiO.sub.2, La.sub.2 O.sub.3, and Ta.sub.2 O.sub.5. In some embodiments, the glasses also contain a small proportion of Cs.sub.2 O. The glasses have very low electrical resistivity, are stable against devitrification, and are readily melted and formed into shapes which are suitable for glass electrodes.

Abstract: The present invention concerns sodium silicate and sodium aluminosilicate glass compositions which contain specified proportions of tantalum oxide and glass electrodes made therefrom, which are particularly sensitive to sodium ions in aqueous solutions containing sodium ions and other monovalent cations. These glasses represent an improvement over sodium aluminosilicate glass elctrodes of the type disclosed in U.S. Pat. No. 2,829,090.

Abstract: Apparatus and method for the measurement of a cell current. A polarographic cell, which may be a two or three electrode system, furnishes a cell current which is a measure of a particular constituent of a material under test in the cell. The electrodes are continuously washed by a buffer solution which gives a base line or steady state current. The current from the cell is converted to a voltage for ease of measurement. The first derivative with respect to time is taken of the voltage. When this rate of change of voltage exceeds a pre-selected level, a signal is generated. This signal causes a sample and hold unit to hold and present as a constant output the voltage level at that time. This is the steady state value. The signal also resets a peak detector which accepts the cell voltage and tracks its value until a maximum is reached. Then, the maximum value is held as a constant output quantity.