Abstract: A sensor uses an immobilized affinity component capable of interacting with analyte species and being associated with a conducting polymer such that the interaction of the affinity component and the analyte induces change in the electrical properties of the polymer. An AC signal is applied to the polymer, and the induced change in impedance resulting from the interaction is measured. The impedance is measured at a frequency or frequencies corresponding to a peak or peaks in the relationship between frequency and impedance change for the polymer and the analyte. The measurement may be made by reference to the imaginary or real component of impedance. The polymer may be in the form of a layer bridging two electrodes between which the impedance is measured. The two electrodes may together define an interdigitated electrode assembly.

Abstract: A sample analyzer incorporates a sensor unit for providing a desired analysis of a sample. The analyzer includes a first body portion having a sensor surface (of the sensor unit) to which a sample is applied for effecting the analysis, a second body portion which is openable and closable together with said first body portion, a chamber incorporating the sensor surface when the first and second body portions are in the closed position, at least one reservoir for holding a treatment liquid and is capable of communicating with the chamber and providing a supply of treatment liquid to the chamber when the body portions are closed.

Abstract: Sensor devices for examining fluid samples having, between the sample under examination and a detector, a membrane made of polyvinyl chloride in un-plasticized form. This membrane material acts as a barrier to paracetamol and sugars but is permeable to hydrogen peroxide and to oxalate, so these species can be determined after passing through the membrane. When they are not present as such in the sample, they may be formed from analytes which are sought (e.g. by enzymic action, which is especially applicable to the determination of glucose, using an oxidase enzyme). The membranes may be made by solvent casting, conveniently to a thickness of 10 to 40 .mu.m, and used in electrolytic systems with a platinum anode. The membrane material can be formed into multi-layer membranes, which may incorporate layers of material to protect it or modify the permeability, or added materials for example enzymes.

Abstract: Sensor devices for detecting components in fluid samples, especially by electrolytic analytical methods, comprising a detecting means (usually an anode, especially one of platinum) surrounded by a selectively permeable membrane barrier composed of a mixture of polyvinyl chloride and polyaryl sulphone polymers. Preferred proportions of the polymers are 1 to 9 parts of polyaryl sulphone for each part of polyvinyl chloride, and the mixture may be formed into membranes by solution casting. Preferably this barrier is used with an inner membrane, especially of porous polycarbonate. In use, these polymer mixtures are especially useful in their selective permeability to glucose. Also provided are methods for their use in analysis, and the polyvinyl chloride/polyaryl sulphone polymer compositions themselves and membranes made from them.

Abstract: Enzyme electrodes having the enzyme enclosed within liposomes supported on, or in a membrane and immobilized therein are provided. The liposomes may be made using lipids and conveniently by "reverse phase evaporation". The enzyme electrodes incorporate conventional electrode elements, e.g., THE Clark electrode pair (Platinum/Silver) and additional membranes or screens, and used particularly in amperometric measurements. The enzyme can be an oxidase and is useful for measurement, directly or indirectly, of low molecular weight species generated by enzymic action, and effective for study of biological fluids.

Abstract: Sensor devices comprising enzyme electrodes incorporating a microporous membrane coated with the carbonaceous material known as "diamond-like carbon" (most conveniently deposited by decomposition of a hydrocarbon, induced by radiation or a high electric field). The membrane material is preferably a polycarbonate and its thickness preferably less than 10 microns, and the coating is preferably 0.01 to 5 .mu.m thick. The preferred porosity is provided by pores of the order of 0.05 to 0.01 microns. The coated membrane imparts high resistance to fouling by contact with whole blood, extends the linearity of the electrode response over a substantially greater range, e.g. in the analytical determination of glucose in blood, and combines a high degree of restriction to passage of interferents while retaining high permeability to hydrogen peroxide and oxygen. Most conveniently used for amperometric measurements, especially using a Clark electrode pair, with an "active" anode of platinum.

Abstract: A sensor of the enzyme-electrode type containing a layer of porous material of restricted permeability between the enzyme and a sample to be analysed. The porous material has a percentage porosity not greater than 5% and preferably in the range 0.005% to 0.5%.

Abstract: A sensor of the enzyme-electrode type comprising an electrode and a membrane permeable to liquids and solutes which is positioned between the electrode and a specimen containing the analyte to be determined, is characterized by the fact that a layer of a porous material, positioned in the membrane between the enzyme-containing layer and the specimen, has been treated to at least partially fill the pores with a liquid of limited volatility which is not significantly soluble in water and is to some degree a solvent for the analyte.

Abstract: A membrane for an enzyme-electrode type sensor treated to increase the range of linearity of the sensor response.

Abstract: A membrane particularly for use in a sensor of the enzyme-electrode type which comprises one or more layers of material and an enzyme-containing layer and in which one layer is formed from a sulphonated or unsulphonated polyarylsulphone or a sulphonated or unsulphonated polyarylketone. The specification also relates to a non-enzymic sensor having a membrane including a layer formed from one of these polymers. Methods for determining an analyte using an enzymic or non-enzymic sensors are also included in the scope of the invention.