Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – For organic compound
Reexamination Certificate
1999-09-27
2001-03-13
Tung, T. (Department: 1743)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
For organic compound
C204S415000, C422S082060, C422S084000
Reexamination Certificate
active
06200459
ABSTRACT:
This invention relates to an analytical method and apparatus useful for the determination of ethanol in a fluid sample.
Many forms of analytical methods and apparatus have been proposed for the detection and measurement of various components in fluid samples, and commonly these rely on some form of membrane to control the extent to which the components present in a sample under examination can gain access to a detector (e.g. an electrode) at which they can then be detected and determined. Especially in electrolytic methods it is well known to make sensors using membranes to separate the media being analysed from the active electrode itself.
The main function of the membrane is to separate, as far as possible, those components which are desirable (i.e. can participate in the reactions at an electrode on which the desired determination depends) from interferents - i.e. compounds which may be present but are undesirable because they either interfere with the progress of the desired determination reactions or take part in reactions of their own which compete with those of the component sought and distort or overwhelm the signals which are to be measured. The forms of construction have much in common with each other, and mainly differ in the nature of the membrane or media within it or combined with it in some way.
Some forms of sensor devices rely on the components used to make the membrane, while others rely on the mode of fabrication of the membrane, selecting its physical properties (for example its porosity) or treatments given to it, as these factors can control its effectiveness and selectivity in use.
Other forms of sensors incorporate an enzyme, which converts one substrate compound or analyte into another which may then be more easily measured. Especially, it is known to use oxidase enzymes, which generate hydrogen peroxide—a substance which can be measured very conveniently and accurately by electrolytic methods, especially amperometric methods, and thereby provide a measure of the compound giving rise to the hydrogen peroxide. An example is European Patent No. 216577 which specifies an enzyme electrode sensor with a porous membrane barrier of a specified low (>5%) porosity.
Polyvinyl chloride (PVC) has been proposed as a material for the fabrication of membranes for sensors. It has been proposed for use in plasticised form, as described in European Patent No. 575412, where the plasticiser performs the necessary part of enabling the membrane to function and the PVC only serves to “carry” the plasticiser.
PVC in un-plasticised form has also been proposed for use as a membrane in European Patent No. 652942. In this, a membrane of un-plasticised PVC is shown to possess a selective permeability towards hydrogen peroxide and oxalate. The reason for this selective permeability of un-plasticised PVC itself is not understood, and the effect is surprising as it is not logically related to molecular size and/or charge. No indication or guidance has been given therein of any other species (if any) to which the PVC might be permeable, or why it should be permeable at all.
Such known sensor devices, utilising various membrane materials, have been aimed principally at the analysis of fluids for the presence of sugars, especially glucose, and other substances which may be oxidisable by enzyme action to form hydrogen peroxide. Examples of fluids described as being analysed by these prior devices include biological media for example blood and fruit.
We have now found that a membrane of un-plasticised PVC also has the surprising property of being permeable to ethanol. This is unexpected, as the known permeability of un-plasticised PVC (particularly as described in European Patent No. 652942) is so limited and unpredictable, and is very valuable because it can provide the basis for analytical methods and apparatus for detection and determination of ethanol by selective diffusion of this compound from a fluid sample. It is especially valuable because there is a great need for a convenient and efficient means which can be used for analysing and/or monitoring products in which alcohol (ethanol) is present and processes in which it is produced or present. Uses to which the discovery can be applied include, for example, (a) fermentation processes such as brewing and wine making, (b) the analysis of beer, wines, and other alcoholic liquids, drinks and the like, and (c) examination of process liquids, effluents and other media in which the presence of ethanol may require monitoring and/or control (because it may be either desirable or undesirable) for example for legal purposes.
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Christie Ian Mcintyre
Vadgama Pankaj Madganlal
Pillsbury & Winthrop LLP
Sensalyse Holdings Limited
Tung T.
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