Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1997-09-30
2001-11-27
Warden, Sr., Robert J. (Department: 1744)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S420000, C204S422000, C204S435000
Reexamination Certificate
active
06322680
ABSTRACT:
APPLICATION AREA
The invention relates to devices for ion composition and redox potential monitoring in process fluids, natural water and sewage, and specifically, a multipurpose ion-selective sensor.
BACKGROUND OF THE INVENTION
Numerous ion-selective sensors designed for monitoring of hydrogen ions in various process fluids are widely known.
Such examples include, in particular, a ion-selective sensor described by P. Meier, A. Lohrum and J. Gareess (Editors) in the study, “Practice and Theory of pH Measurement”, Ingold Messtechnik A G, CH-B902 Undorf/Switzerland, 1989, p. 15. This combined sensor comprises a glass tube body incorporating glass indicator and reference electrodes filled with a liquid electrolyte.
Another known ion-selective sensor (a Switzerland's Ingold booklet “pH/Redox Measurement in Biotechnology. pH-Electrodes. Industrial Probes. Sensors,” Ingold Messtechnik A G, CH-8902 Urdorf/Switzerland 1990, p. 10) has a similar design, but its reference electrode is filled with a gel-type electrolyte.
The both above mentioned sensors have a monolithic glass design and require refillings of their reference electrodes. These sensors are only suitable for predefined spatial positions and are inoperable in harsh conditions (elevated temperatures and those below 0° C., high pressures, zero-gravity and other conditions). Sensors intended for redox potential monitoring are widely employed at present. For instance, a sensor with a reference electrode filled with gel electrolyte and an indicator electrode with a platinum or gold sensing element have been described in a booklet titled “PH/Redox Measurement in Chemical Processes. pH-Electrodes. Industrial Probes. Sensors,” published by Ingold Messtechnik A G, CH-8902 Urdorf/Switzerland, 1990, p. 16.
Similarly to the above mentioned ion-selective sensors, this device comprises an integral, monolithic glass design which is only operational in a predefined spatial position and is not intended for harsh conditions.
Another known ion-selective sensor (the US' Foxboro Company booklet, “pH/ORP/ISE Sensors B71 pH Series,” The Foxboro Company, Foxboro Mass. 02035-2099, 1993, p. 1) was designed for fluorine and hydrogen ion activity monitoring and is suitable for redox potential monitoring applications.
This sensor incorporates a plastic housing tube where a detachable indicator electrode is rigidly fixed in addition to a reference electrode that has a hollow body filled with liquid or gel electrolyte containing a solid dispersed material which forms a spatial structure that is freely movable inside the reference electrode. An indicator electrode filled with liquid electrolyte, together with a solid ion-selective sensor, are installed into the housing tube for ion activity monitoring, and an indicator electrode with a platinum sensing element is inserted into the housing tube for redox potential monitoring.
Compared to the previously mentioned sensors, the claimed device is more flexible in use and therefore has wider applications.
However, all above mentioned disadvantages apply to the latter sensor. They are attributed to the liquid or gel-type electrolyte present in the reference electrode and the liquid electrolyte inside the indicator electrode. This requires frequent refillings of the reference electrode electrolyte, poses spatial limitations for sensor operation and restricts harsh-environment applications.
DETAILED DESCRIPTION OF THE SPECIFIED EMBODIMENTS
The proposed invention is built around the design of a multipurpose ion-selective sensor in an embodiment that would eliminate electrolyte movements inside the electrodes and its entry into the analysed liquid thereby making it functional in any spatial position, critical operating environments, and under any ion composition and redox potential.
This challenge has been met by a multipurpose ion-selective sensor which incorporates a housing tube with a detachable indicator electrode that is fixed to, and is electrically connected with a measurement transmitter, whereby the electrode has an indicator system with a sensing membrane immersed into the analysed liquid; the reference electrode comprises a hollow body with electrolyte filled with a solid dispersed material forming a spatial structure in the electrolyte, a potential-forming semi-element and a connecting member which is contacting the analysed liquid. According to the proposed layout, both the indicator system and its sensing probe have a solid-state design; the reference electrode has an internal surface, and its spatial structure is rigidly linked with this surface and the connecting member.
In this way, the proposed ion-selective sensor employs electrodes which are essentially immune to gravity and enable any spatial position for normal operation. This design eliminates electrode damage at high temperatures (around 200° C.) high pressures (around 5 MPa), zero-gravity conditions and low temperatures of some −60° C., thereby ensuring full operability in extreme conditions. Moreover, the design eliminates the electrolyte entry from the reference electrode and thus greatly extends the useful service life of the claimed sensor. This sensor design enables its application for redox potential measurements in analysed liquids with no regard to sensor spatial position and operating environment.
One and two-chamber designs are available for the reference electrode. For the both embodiments, the electrolyte spatial structure in each chamber of the reference electrode is rigidly linked with internal walls of said chambers, the potential-forming member, each connection member and external wall of the internal chamber.
In the single-chamber reference electrode embodiment, the said rigid link of the spatial structure is achieved by a solid dispersed material of the reference electrode electrolyte, in quantity sufficient for 5-30 wt. % concentrations whereby the said material contains acrylamide and NN
1
-methylemebisacrylamide monomers in proportions of 5-35 weight parts of acrylamide per one weight part of NN
1
-methylemebisacrylamide as well as a monomer polymerisation initiator; in the two-chamber reference electrode embodiment, the second solid dispersed material is present in the internal electrolyte, in quantities suitable for 0.1-5 wt. % concentrations and with a similar composition to the solid dispersed material of the electrolyte contained in the reference electrode body.
This enables various designs of solid-electrolyte indicator electrodes to be mounted in the sensor housing tube where the said electrodes should be the most appropriate for individual analysed liquids and, most importantly, will enable the solid-state configuration of their indicator system and the sensing member.
For instance, the indicator electrode can be configured with a hollow glass body with its one end portion incorporating an indicator system comprising an envelope made of sensitive glass, and an internal surface where the solid electrolyte is connected with a measurement transmitter by an electric conductor. The said sensitive glass can be either a ion-selective grade or a glass sensitive to electron transfer into redox processes.
An indicator electrode can be installed for individual liquids under analysis where the electrode can be either selective to a specified ion of the analysed liquid or, optionally, be suitable for monitoring the redox potential.
For example, the indicator electrode can comprise an inert material body with its indicator system located at one end portion, the said system comprising a ion-selective membrane having an internal surface with a solid electrolyte thereon and connected to the measurement transmitter by an electric conductor; alternatively, an indicator electrode can be made with an inert material body and its indicator system provided in one end portion, with the said system comprising a noble-metal sensitive membrane connected to the measurement transmitter by an electric conductor.
The sealed sensor housing tube design and reliability improvements as well as easier sensor maintenance, assembly an
Advanced Biosensors
Foley & Lardner
Olsen Kaj K.
Warden, Sr. Robert J.
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