Plastic electrodes have been developed for measuring pH in the human gastrointestinal tract. The electrodes have a plastic hydrogen ion sensitive membrane sealed to a length of fluid filled PVC tubing. Two recently developed hydrogen ion sensitive ligands have been examined. Their operational characteristics have been described. These electrodes have an electrical response of 52 to 58 mV/pH unit change in the range pH 4-9, with a diminished response outwith this range. They have a low resistance value and a fast response time of one second to reach 90% of their maximum response. The electrodes can be passed down the biopsy channel of an endoscope to obtain mucosal pH readings under direct vision. Readings obtained in this way using plastic electrodes are comparable to those obtained with glass electrodes. Alternatively, these electrodes can be joined to a Crosby capsule, allowing continuous recording of mucosal pH through to the jejunum during jejunal biopsy procedures. These electrodes can be used repeatedly or may be acceptable as inexpensive disposable items for sterile clinical use.
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