RU2068710C1 - Ph-probe - Google Patents

Abstract

FIELD: medical equipment, intended for determining the concentration of hydrogen ions (pH) of biological media. SUBSTANCE: the pH-probe has measuring antimony electrodes in the form of rings rigidly secured on thin-walled sleeves, sealed hose fitted onto the sleeves, chlorine-silver comparison electrode positioned in a non-metallic casing with an electrolytic switch, and conductors connecting the electrodes to the connector. The pH-probe uses an independent casing of the chlorine- silver electrode supplemented with a detachable bowl- shaped adapter, whose bottom has a through hole through which a capillary-porous wick is passed. Part of the wick positioned inside the adapter is impregnated with conductive paste and contacts with the electrolytic switch of the chlorine-silver electrode via a layer of this paste. The other part of the wick is positioned outside the adapter, and the hose working end is sealed by means of the end antimony electrode made in the form of a cylinder and rigidly secured in the hole on the hose end. The hose working end can be sealed by attachment of a non-metallic end-piece on the sleeve of the end antimony electrode. EFFECT: enhanced accuracy. 3 cl, 1 dwg

Description

 The invention relates to medical equipment and can be used to determine the concentration of hydrogen ions (pH) of biological media, in particular for gastroenterological pH meter, that is, pH meter in the human esophagus, also in technical pH meter, for example pH control of various (liquid, etc.) environments in the food industry.

 A known endoscopic pH probe for gastroenterology, consisting of a measuring antimony electrode and calomel electrode, which are connected to the connector by individual conductors.

 Known pH probe containing calomel (Hg / Hg CI) reference electrode, measuring antimony electrodes fixed in an elastic tube and conductor, connected to the electrodes and passing inside the tube.

 The main disadvantage of these calomel pH probes is the presence in the body of the calomel electrode for comparison of such toxic components as mercury and mercury chloride. The ceramic case has an opening (electrolytic key) through which mercury can enter the human esophagus. The use of mercury reduces environmental safety and requires special safety measures in the production and operation of calomel probes.

Known silver chloride electrode for bioelectric studies of man, containing a silver chloride half cell (Ag / AgCl), which is placed in a bowl-shaped housing of an electrically conductive material with an electrolytic key in the form of a porous disk impregnated with an electrolyte [3]
Such electrodes are suitable only for removing the biopotential from the skin of the subject, and not for measurements in a liquid medium as part of a pH probe, since when using this electrode as a reference electrode for a pH probe, it is impossible to calibrate the pH probe in buffer solutions and test it for reliability in measured liquid media. This is explained by the fact that upon contact of a porous pad impregnated with an electrolyte (electrolytic key), an electrode with a liquid medium, the buffer solution or the measured liquid medium is contaminated by the electrolyte from the porous pad due to dissolution and diffusion processes.

 Known pH probe (prototype), containing measuring antimony electrodes in the form of rings, rigidly mounted on thin-walled bushings, a sealed hose stretched on the bushings, a silver-silver reference electrode placed in a non-metallic case with an electrolytic key and conductors connecting the electrodes to the connector [4] The case of a silver chloride electrode consists of a non-metallic base and a ceramic cap with a hole (electrolytic key). Conductors pass inside the hose of an elastic polymer tube.

 The advantage of this pH probe with a silver chloride comparison electrode in comparison with the first and second pH probes is the environmental safety of its production and operation by replacing toxic components (mercury and mercury chloride) with silver and silver chloride. Therefore, a pH probe with a silver chloride reference electrode corresponds to the hygienic requirements for medical devices.

 However, the latter pH probe also has disadvantages. So, such a probe is characterized by an organic time of continuous operation (not more than 2 hours) in liquid media in the case of repeated (at least 100 times) use of the probe. This drawback is due to the design features and the specifics of the silver-silver reference electrode placed in a ceramic cap with a diameter of about 3 mm. In particular, the potassium chloride solution is washed out through an opening in the ceramic cap. Therefore, this probe cannot be used in the case of daily pH-metry with multiple operation (at least 100 cycles). It is also difficult to test such probes for reliability in liquid media for a long time due to a decrease in their resource. In addition, it is undesirable to introduce these probes through the nose of the patient being examined at a daily pH meter in the esophagus and gastrointestinal tract due to the relatively large diameter of the casing (≈3 mm) of the silver chloride electrode, which is also their drawback.

 The technical result of the invention is the possibility of calibrating the pH probe in buffer solutions, testing it for reliability in liquid media and increasing the reliability of the pH probe during long-term measurement of a pH-liquid medium, especially with repeated operation.

 This technical result is achieved by the fact that in the known pH probe containing antimony measuring electrodes in the form of rings rigidly located on thin-walled bushings, a sealed hose stretched on the bushings, a silver-silver reference electrode placed in a non-metallic case with an electrolytic key and conductors connecting the electrodes with a connector, the pH probe is made with an autonomous silver chloride electrode housing containing a removable cup-shaped nozzle, in the bottom of which there is a through hole through which a capillary-porous wick, part of which is located inside the nozzle, is impregnated with an electrically conductive paste and contacts the silver chloride electrode with an electrolytic key through a layer of this paste, the other part of the wick is located outside the nozzle, and the working end of the hose is sealed by means of an end antimony electrode made in the form of a cylinder and rigidly fixed in the hole at the end of the hose.

 The working end of the hose can be sealed by attaching a non-metallic tip to the sleeve of the end antimony electrode.

 The essence of the invention is as follows. The stand-alone case of the silver chloride comparison electrode of the pH probe contains a removable cup-shaped nozzle. The presence of this nozzle, made of non-metallic material, provides the possibility of calibrating the pH probe in buffer solutions, and its testing for reliability in liquid media and expands the scope of its application due to the ability to measure pH-liquid media. Moreover, the design of the silver chloride reference electrode itself, in particular its housing, does not play a big role. So, in the case of a silver-chloride electrode in a non-metallic case with an electrolytic key in the form of a porous disk impregnated with an electrolyte, for example, an electrically conductive paste, a removable nozzle protects the electrolytic key from contact with a buffer solution or measured liquid medium, that is, it eliminates the dissolution (washing out) of the electrolyte from the porous disk in a liquid medium, as well as contamination of the latter, in particular, a buffer solution. This result is achieved due to the fact that only the outer part of the capillary-porous wick in contact with the liquid medium is located outside the removable nozzle. The silver chloride electrode body and the nozzle itself are not in contact with the liquid medium. The part of the wick located inside the nozzle is impregnated with an electrically conductive paste and is in contact with the silver chloride electrode electrolytic key through a layer of this paste.

 Sealing the working end of the hose in one way or another eliminates the ingress of liquid medium (electrolyte) into the internal cavity of the hose, which ensures the reliability of the pH probe in a liquid medium.

 To ensure the tightness and strength of the composite hose of the pH probe with antimony electrodes, all one-piece joints are made by bonding with polymer adhesives.

 In FIG. 1a, b shows the pH probe of the proposed design and its variant, respectively.

 The pH probe contains antimony measuring electrodes 1, made in the form of rings, rigidly mounted on thin-walled bushings 2, a sealed hose 3, stretched on the bushings. As a hose, a polymer elastic tube is used, for example, a polyethylene radiopaque. The connections of the elastic tube (hose) with the bushings 2 are made one-piece by means of polymer glue. The end measuring electrode is made in the form of an antimony cylinder 4, on which a hose is pulled (Fig. 1a). Moreover, to ensure tightness in this case, the connection of the antimony cylinder with a hose is made by gluing with polymer glue 5.

 In addition, the end of the hose can be sealed from getting into the pH probe of a liquid medium by gluing a plastic (or ceramic) tip 6 with glue 5 (Fig. 1b), the pH probe contains a silver chloride comparison electrode 7, which is placed in a stand-alone non-metallic case 8 with an electrolytic key 9. The electrolytic key 9 may be made in the form of a hole filled with an electrode, or in the form of a porous disk impregnated with an electrolyte. As the electrolyte, for example, an electrically conductive paste is used.

 Conductors 10 connect the antimony measuring electrodes and a silver chloride electrode with a low-frequency connector 11. Moreover, the silver chloride electrode can be connected to a detachable removable conductor.

 The case of silver chloride electrode 8 contains a removable cup-shaped nozzle 12, in the bottom of which there is a through hole located opposite the electrolytic key 9 in the housing of the silver chloride electrode.

 A nozzle made of plastic is connected to the housing by a detachable connection (threaded, by tightening, by means of screws, etc.). A capillary-porous wick 13 passes through the through hole of the nozzle, part of which, placed inside the nozzle, is impregnated with an electrolyte (electrically conductive paste) and is in contact with an electrolytic key 9 made, for example, in the form of a porous disk made of foam rubber impregnated with electrolyte. As the electrolyte, an electrically conductive electrode paste 14 is used, which can fill the cavity between the nozzle 12 and the silver chloride electrode case 8. Another part of the wick 13, made, for example, in the form of a cotton thread, leaves the nozzle at a distance of about 20. 100 mm.

 The work of the pH probe.

 In the case of pH metering in the human esophagus, the probe is used with a nozzle on a silver chloride electrode only when it is calibrated in buffer solutions. Since the silver chloride comparison electrode has constant potential, therefore, when the working part of the pH probe, namely the hose 3 with antimony measuring electrodes 1.4 and the outer part of the wick 13, is immersed in a liquid, a potential difference is formed, the value of which is determined by the concentration of hydrogen ions (pH ) in a liquid medium. This potential difference by means of conductors 10 and connector 11 is fed to the secondary Converter for further signal conversion. It should be noted that the nozzle 12 is used only when calibrating pH probes in buffer solutions and when testing them for reliability in liquid media.

 When measuring pH in the human esophagus, the nozzle is removed from the silver chloride electrode body, the silver chloride electrode is attached to the handle of the probe, and the working part of the pH probe, i.e. a hose with measuring electrodes is introduced into the esophagus through the nose or mouth of the subject.

 A pH probe can also be used to measure the pH of a liquid medium in the food industry for a long time (more than a day). In this case, after calibrating the pH probe in the buffer solutions, the nozzle is not removed in the silver chloride electrode case, and the outer part of the wick 13 and the pH probe hose are immersed in the measuring liquid medium. In the case of a multiple measurement mode, the electrolyte inside the nozzle is updated as needed. When measuring the pH of a liquid medium, the distance between the end face of the nozzle and the level of the liquid medium is about 5.20 mm, that is, the nozzle itself does not come into contact with the liquid medium.

 Thus, the proposed design of the pH probe makes it possible to calibrate and test the reliability of pH probes in a liquid medium. Moreover, the pH probe can be administered both through the nose and through the mouth of the subject due to the possibility of reducing the diameter (from 3 mm to 2 mm). The accuracy of calibration of pH probes in buffer solutions was also improved by reducing their contamination with electrolyte from a porous disk. The proposed design of the pH probe will allow it to be used repeatedly for long-term pH measurements of a liquid medium, for example, in the food industry.

 Tests of such probes have confirmed their effectiveness.

Claims (2)

 1. A pH probe containing antimony measuring electrodes, including in the form of rings rigidly mounted on thin-walled bushings, a sealed hose stretched over the bushings, a silver-silver reference electrode placed in a nonmetallic case with an electrolytic key, and conductors connecting the electrodes to the connector characterized in that the pH probe is made with an autonomous silver chloride electrode housing, further comprising a removable cup-shaped nozzle, in the bottom of which there is a through hole through which a capillary a porous wick, part of which located inside the nozzle is impregnated with an electrically conductive paste and contacts the silver chloride electrode with an electrolytic key through a layer of this paste, the other part of the wick is located outside the nozzle, while one of the antimony measuring electrodes is made in the form of a cylinder and is rigidly fixed in the hole at the end hose to seal the latter.  2. The pH probe according to claim 1, characterized in that the working end of the hose is sealed by securing a non-metallic tip on the sleeve of the terminal antimony electrode.