Yellow Springs Instruments

Table 6.2 Analytes measured by membrane biosensors (Yellow Springs Instruments)...

Resin-bound enzyme was packed in Pharmacia C 10/20 jacketed columns for kinetic analysis. Glucose concentrations in hydrolyzates were determined with a YSI Model 27 glucose analyzer from Yellow Springs Instruments. 

Immobilized glucose oxidase with a hydrogen peroxide electrode Yellow Springs Instrument Co., USA TO A Electronics Ltd., Japan Fuji Electric Co. Ltd., Japan... 

Glucose and sucrose in condensed milk (these sugars are not found in raw milk) diluted with phosphate buffer can be measured using analysers made by Yellow Springs Instrument Co. (www.ysi.com/index.html). 

This lead to the development of the first glucose analyser for the measurement of glucose in whole blood (Yellow Springs Instrument 23 YSI, 1974). 

Glucose in pre-treated ice-creams, drinks, molasses and flour has also been determined with a glucose oxidase based nylon electrode. The results were similar to those obtained by the Yellow Springs Instrument glucose analyser and a Boehringer Mannheim glucose test-kit (10). 

University of Washington, 276 Yellow Springs Instrument Company, 40... 

The glucose was determined enzymatically (Yellow Springs Instruments). The response time of the complete analyzer system was ca. 37 min, of which 5 min are due to the transfer distance of 3 m between the reactor, filtration module and analyzer system. The continuous air segmented flow analyzers have the disadvantage that after 3-4 days operation, microorganisms growth was detected in the non aseptic analyzer system. 

Oxygen electrode system (e.g., Yellow Springs Instruments Model 53)... 

Oxygen electrode system with recorder—For example, Yellow Spring Instruments Model 53 oxygen electrode (Yellow Springs, OFI), or equivalent, attached to a linear 10-mV recorder. Five of these units will be required. 

Although conductance/resistance meters are available commercially (e.g., YSI, Yellow Springs Instruments, and others), the simple ac Wheatstone bridge of Fig. 1 is adequate and better illustrates some of the principles for accurate conductivity measurements. Here the ionic solution is placed in the conductivity cell, which is part of abridge subjected to a small ac voltage from a 1-kHz oscillator. The condition of balance for the bridge is detected with an oscilloscope and requires that the alternating potential at points B and D be of equal amplitude and exactly in phase. This corresponds to a balance condition... 

Yellow Springs Instrument Co., Glucose and YSI Immobilized oxidases... 

The solution conductivity was measured using a Yellow Springs Instrument conductivity meter (YSI Model 34) with a high pressure conductivity cell (cell constant of 0.0044 cm ). The high pressure cell consisted of ten stacked, stainless steel disc electrodes (10-mm diameter discs), insulated with Teflon washers. The meter is particularly well suited for use with this type of cell because capacitance errors are minimized by the active circuit and electrode over-potential is eliminated by measurement potentials of less than 1 volt. 

Assemble a Clark electrode (with a fresh membrane, if necessary), constant temperature bath, constant voltage source, and recorder following the manufacturer s instructions. In the subsequent discussion the Yellow Springs Instrument s Clark electrode and sample chamber are used. 

Initial velocity measurements in kinetic experiments were carried out by following the oxygen consumption with an oxygen electrode (Yellow Spring Instruments 1 mL chamber). 

Solution pH was measured with a Ross combination electrode and Orion model 601A pH meter. Specific conductance was measured with a Yellow Springs Instruments model 32 conductance meter and cell. Cations were determined by inductively coupled atomic-emission spectroscopy. Sulfate and chloride were determined by ion chromatography. Bicarbonate was determined by titration with H2SO4 to pH 4.5. 

The next stage was achieved in 1967 by Updike and Hicks, who entrapped GOD in a gel of polyacrylamide, thus increasing the operational stability of the enzyme and simplifying the sensor preparation. Further investigations by Reitnauer (1972) enabled the successful application of an enzyme electrode in a prototype blood glucose analyzer. In 1975 Yellow Springs Instrument Co. (USA) commercialized a glucose analyzer (model 23 A) which was based on a patent by Clark (1970). The Lactate Analyzer LA 640 by La Roche (Switzerland) followed one year later. In this instrument the enzyme is dissolved in a buffer in a reaction chamber placed in front of the electrode. 

Electric company (Osawa et al., 1981). The membrane developed by Newman (1976) is being used in the 23 A glucose analyzer (Yellow Springs Instrument Co., USA, see Section 5.2.3). Lindh et al. (1982) showed that the cellulose acetate membrane is not truly selective for H2O2, but only decreases the permeation of larger molecules. The sensor was 3 times more sensitive to the glycolysis inhibitor paracetamol than to glucose. The membrane permeability was shown to depend on membrane age. 

An alcohol electrode incorporating AOD immobilized in a hydrogen peroxide-selective sandwich membrane is commercially available from Yellow Springs Instrument Co. (USA). 

In contrast, the glucose analyzers of Yellow Springs Instrument Co. (YSI), Fuji Electric, and Daiichi measure only the true glucose concentrations in plasma and serum samples. Upon direct injection of whole blood into the Fuji instrument the measured values are too low by 13% (Niwa et al., 1981). This trend is confirmed by the correlation equation obtained with the AutoSTAT instrument of Daiichi as applied to whole blood samples ... 

Yellow Springs Instrument Co. 49TA 20 to 43°C 0.01°C 0.25°C 435 25-100 Portable battery powered 4-Digit LCD display... 

Yellow Springs Instrument Co. 46TUC 0 to 51°C 0.05°C 0.15°C PLATINUM RESISTOR TYPE 618 25-100 6 Input channels, recorder output, analog meter... 

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