Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-03-10
1996-10-22
Bell, Bruce F.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204403, 435817, 4352871, 4352879, 4352887, G01N 2726
Patent
active
055672906
DESCRIPTION:
BRIEF SUMMARY
This invention relates to sensor devices such as are used in the determination of a component or components which may be present in a fluid sample, such as a physiological fluid (e.g. blood) or other fluids of biological origin (e.g. fruit), process fluids or effluents.
Many forms of sensor have been proposed, 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 an electrode, at which they can then be detected and determined. Especially, it is well known to make sensors using membranes to separate the media being analyzed 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 take part in the reactions at the 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 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 very accurately by electrolytic methods, especially amperometrically. An example is European Patent No. 216577 (of ICI PLC) which specifies an enzyme electrode sensor with membrane barrier of low (>5%) porosity.
Materials which have been proposed for the fabrication of membranes for sensors include polyvinyl chloride (PVC), but only in plasticized form, as described in European Patent Application No. 92302131.5, where the plasticizer performs a necessary part of the function of the membrane.
Such known sensors, utilising various membrane materials, are very valuable in analytical techniques and the analysis of biological fluids (e.g. blood) for the presence of substances considered critical for medical reasons--e.g. glucose and other materials which may be oxidizable or reducable, or have toxic properties.
We have now found that the selectivity of such a membrane-enclosed sensor can be significantly and surprisingly modified and improved by making the membrane of polyvinyl chloride (PVC) itself, in un-plasticized form.
Thus according to our invention we provide an improved sensor device comprising means for detecting components present in fluid samples and providing an output representative of the content of said component comprising a detecting means and a membrane barrier between the detecting means and the sample to be analyzed, characterised in that the membrane barrier is composed of polyvinyl chloride (PVC) itself, in un-plasticized form.
The detecting means is most conveniently of one of an electrochemical nature, but other types (e.g. spectrophotometric or optical detecting systems) may be used if desired. The detecting means will usually comprise an electrode system and a liquid or gel phase electrolyte-containing medium. In most applications the electrolyte will be aqueous (i.e. aqueous or aqueous-based) but the use of non-aqueous electrolyte media (for example organic-based media) is not excluded.
According to our invention we also provide a method for determining a component in a fluid sample, which comprises contacting the sample with a sensor device as defined above.
Especially, in the devices and method of
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Benmakroha Yazid M.
Christie Ian M.
Reddy Subrayal M.
Vadgama Pankaj M.
Bell Bruce F.
The Victoria University of Manchester
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