An ion-selective electrode having an ion-selective membrane in direct contact with an electrical conductor is provided in which the membrane coats an uninsulated zone surrounded by insulation on the surface of a conductor which is coated with a layer of electrical insulation. The membrane overlays the insulation surrounding the insulation free zone and comprises a polymer which is generally of sufficiently similar composition to that comprising the electrical insulation layer so that it adheres to the insulation forming a membrane with increased structural strength. Embodiments of the electrode containing phosphatidylcholine in the ion-selective membrane have increased sensitivity.
A polymeric membrane electrode gives potentiometric responses to macromolles, such as protamine, in solution or biological specimens. A protamine-responsive membrane includes a lipophilic cation-exchange material for ionic macromolecules in a specially formulated plasticized, polymeric matrix material. Potentiometric response to protamine has been observed in membranes comprising 30-70 wt. % polymeric matrix material, such as polyvinyl chloride; 1-3 wt. % salt of a tetraphenylborate, such as potassium tetrakis(4-chlorophenyl) borate or salt of an organophosph(on)ate, such as calcium bis-[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate; and 30-70 wt. % of a plasticizer, such as 2-nitrophenyl octyl ether or tris (2-ethylhexyl) phosphate. The potentiometric response of these membranes to protamine can be used to study the binding interaction of protamine with heparin (both native and low molecular fractions) or to monitor protease activity, for example, by following the rate of degradation of intact protamine or a synthetic substrate by trypsin, as well as to measure protamine concentration in biological fluids, such as blood or plasma.
A sensor for the amperometric assay of cholesterol is provided which comprises a sensing electrode containing a first redox mediator and a reference electrode in simultaneous contact with a reagent strip containing a second redox mediator. The presence of the second redox mediator greatly amplifies the current flow produced by the presence of cholesterol and produces linear correlation of current flow with concentration over an extended range. The sensing electrode comprises a non-conductive support member having an electrically conductive layer containing the first redox mediator. The reference electrode is typically a Ag/AgCl electrode formed by coating an ink containing Ag/AgCl dispersed in a resin on a non-conductive base. The reagent strip is a porous or fibrous carrier, typically a paper, impregnated with a mixture containing the second redox mediator, cholesterol esterase, cholesterol oxidase, horseradish peroxidase, at least one surfactant and at least one stabilizer comprising an aqueous thickening agent. In one version of the sensor, the sensing electrode comprises a support member of polyester film coated with an electrically conductive graphite composition containing dimethylferrocene as the first redox mediator and the second redox mediator comprises 3,3',5,5'-tetramethylbenzidine. The sensor may be constructed in several physical forms. In one form, the sensing and reference electrodes are in the form of strips and the reagent strip is sandwiched between the electrically conductive layers of the electrodes with the reference electrode having a hole, through which the reagent strip is exposed, for the introduction of sample.
Aqueous membrane permeable by mass transport to a charged and uncharged species of interest, comprising a synthetic polymeric material and a surface active agent which is miscible with the synthetic polymer. The surface active agent is distributed throughout the membrane and is present in an amount such as to provide for the permeability of the membrane to the species of interest.
This invention pertains to fluorophoric compositions and methods of their use for enhancing visualization of various constituents of ion selective electrodes.
An ion sensor having an ion selectivity, which comprises an internal electrode of metal/metal salt, composed of an electroconductive layer of at least one metal and a layer of an insoluble salt of the metal in contact with the electroconductive layer, an ion selective membrane whose supporting membrane is composed of a hydrophobic polymer, and an intermediate layer capable of keeping water molecules, provided between the internal solid electrode and the ion selective membrane, where the organic compound having a water-keeping property is polymethylene glycol, polyethylene glycol or polypropylene glycol, each having a molecular weight of 200 to 600, and the inorganic compound having a water-keeping property is calcium chloride, gold chloride, magnesium perchlorate, magnesium fluoride or vanadium chloride dioxide, is suitable for analysis of specific ion species in a biological fluid with practically prolonged maintenance of properties of electrode.
