Antimony electrode assembly and method of manufacture, and use thereof

An antimony electrode for pH measurement is formed with a convex, very smooth tip and sealed within a flexible plastic sheath with just the tip exposed. A reference electrode is provided either separately or in conjunction with the antimony electrode, the reference electrode being sealed within a plastic tube surrounded by an electrolyte. One end of the reference electrode is operatively connected through one end of the tube, to a conductor cable. The other end of the reference electrode terminates spaced internally from the other end of the tube and a plug closes this other end. This plug is formed from a material such as wood, which is saturated with electrolyte that forms an electrolytic connection between the exposed end of the plug of the electrolyte within the tube and hence with the reference electrode in the tube.

BACKGROUND OF THE INVENTION 
This invention relates to new and useful improvements in the manufacture 
and use of antimony electrode assemblies for the measurement of pH either 
orally or internally and with or without a separate or integral reference 
electrode. However, it will of course be appreciated that it can be used 
to measure pH in other environments if desired. One method of manufacture 
of antimony electrode assemblies is described in Canadian Pat. No. 987,388 
dated Apr. 13, 1976. 
This Canadian Patent discloses the method of forming the antimony rod from 
which the relatively small pieces are cut or otherwise detached from the 
rod. 
One of these pieces is then soldered in end to end relationship, by one end 
thereof to one end of a length of silver wire and relatively hard plastic 
is used to coat all of the rod, the solder junction and part of the silver 
wire leaving the distal tip of the rod exposed and it is this tip that is 
used to measure pH. 
However, it has been found that this exposed tip is relatively rough thus 
disturbing the pH readings to the extent that they fluctuate depending 
upon the circumstances. Furthermore, covering the junction between the rod 
and wire, and a portion of the wire has been found to weaken rather than 
strengthen the junction inasmuch as if a bend does occur in the wire above 
the lower end of the relatively hard plastic, the plastic tends to crack 
away relatively easily. 
SUMMARY OF THE INVENTION 
The present invention teaches, among other things, improvements in the 
method of manufacture which contemplates grinding the end of the antimony 
rod which will remain exposed, to a convex substantially hemispherical 
configuration and then highly polishing this convex surface so that it is 
substantially crystallographically undisturbed. The area around the tip of 
the antimony rod is then coated with an epoxy resin which can be cured to 
a relatively hard coating and this coating may extend either part way 
along the rod or all of the way along the rod excluding the soldered joint 
at the other end of the of the rod and any of the silver wire attached to 
the other end by the soldered joint. 
The electrode and all or part of the silver wire is then inserted into a 
flexible TEFLON (T.M.) tube which shields and insulates the antimony 
electrode and the silver wires gives the necessary strength to the 
junction between the electrode and the wire and permits the wire to be 
manipulated within limits so that it can be used in the variety of 
circumstances including esophageal pH monitoring. 
In accordance with the invention there is provided a method of 
manufacturing a pH electrode from a length of antimony rod consisting of 
the steps of; 
(a) grinding the distal end of the antimony rod into a convex 
configuration, 
(b) highly polishing said distal end as close as possible to a single, one 
place crystal face, 
(c) securing a conducting wire by one end thereof to the other end of said 
antimony rod, 
(d) covering part of said rod with a relatively hard epoxy resin but 
leaving the convex distal end bare, 
(e) covering the antimony rod, the junction of the rod with the conducting 
wire and at least part of the conducting wire, with a flexible plastic 
tubing up to but not including the convex distal end of said rod, and then 
(f) sealing the tubing to the antimony rod at least around the bare convex 
distal end, against the ingress of contaminants. 
In accordance with another aspect of the invention there is provided an 
antimony electrode for pH measurement comprising in combination a 
relatively short length of antimony rod secured by one end thereof, as by 
soldering, to one end of a conducting wire, the distal end of said rod 
being convex and substantially hemispherical and having a highly polished 
surface approaching a single, one plane crystal face, a relatively hard 
epoxy resin covering at least part of the length of said rod but with the 
distal end remaining exposed, a flexible plastic tube surrounding said 
rod, the junction of said rod with said conducting wire, and at least part 
of said conducting wire, with said distal end of said rod remaining 
exposed, said portion of said plastic tube adjacent said distal end of 
said rod being in sealing relationship around said rod to prevent ingress 
of contaminants. 
In accordance with a further aspect of the invention there is provided a 
reference electrode assembly comprising in combination a length of tubing, 
an electrolyte permeated plug in one end of said tubing, a reference 
electrode within said tubing and operatively extending from the other end 
thereof in sealing relationship therewith, and an electrolyte within said 
tubing surrounding a portion of said reference electrode within said 
tubing, said electrolyte permeated plug operatively connecting the distal 
end of said plug to the electrolyte within said tubing. 
With the foregoing in view, and other advantages as will become apparent to 
those skilled in the art to which this invention relates as this 
specification proceeds, the invention is herein described by reference to 
the accompanying drawings forming a part hereof, which includes a 
description of the best mode known to the applicant and of the preferred 
typical embodiment of the principles of the present invention, in which:

DETAILED DESCRIPTION 
Proceeding therefore to describe the invention in detail, the antimony, 
which is 99.9% pure, is broken out of a glass encased rod in a manner 
similar to that described in the above identified Canadian Patent. The 
diameter of the rod is approximately between 1-2 mm. The rod is then 
broken or cut into small pieces approximately 2-3 mm long. These pieces, 
when cut, have very rugged ends similar to that shown in FIG. 2. One end 
10 of the antimony piece of rod 11 is then ground to a convex 
substantially hemispherical configuration 10A as shown in FIG. 3 making it 
relatively easy to clean before use. This convex surface 10A is then 
highly polished with a fine pumice. 
This surface 10A is then again polished to an extremely high finish with a 
special metallurgical polish such as JEM-sparkle (TM) a tumbling charge 
repolish manufactured by Lortoner Inc., Seattle, Wash., U.S.A., 98107. 
This is used in order to prevent any distortion of subsequent results due 
to polish residue lodging in micro-crevices which might occur if a polish 
such as Jewellers Rouge is used. Metallurgical polish is inert in this 
respect. 
The purpose of the polishing is to bring this exposed surface as close as 
possible to a single, one plane crystal face that is exposed to the liquid 
or surface being tested. 
Measuring and comparing the ground and polished surfaces one with the other 
may be accomplished by using a Reflexometer in order to confirm what can 
be seen with the naked eye or by magnification. This enables replication 
to take place within design parameters. 
A silver wire 12 is then soldered as at 13 to the other end 14 of the 
antimony electrode 11 in end to end or butt-joint relationship. Relatively 
hard epoxy resin 15 is then used to cover all or part of the electrode 15 
except the face 10A and flexible TEFLON (T.M.) tubing 16 covers the 
assembly and acts as reinforcement and as an insulator. As will 
hereinafter be described in detail, the next step is to completely seal 
the area around the polished tip of the electrode in order to prevent any 
leakage of liquid along the sides and between the sheath and the electrode 
which of course would cause readings to be erratic. 
A suitable epoxy for use in coating all or part of the rod 11 is an epoxy 
manufactured by Hysal division of the Dexter Corporation and listed as 
Hysal IC has been found to be eminently successful in bonding to the sides 
of the electrode in order to prevent leakage. This product is factory 
pre-mixed in a vacuum and placed in ICC vials. The vials are fast frozen 
and maintained in a frozen condition during transportation and storage. 
When ready for use, the vials are individually thawed and the epoxy is 
applied to the total surface of the electrode that has not been polished. 
In other words all of the electrode with the exception of the polished one 
end may be coated and the electrode is then placed in an oven for two 
hours at 60.degree. C. in order that curing may take place. This IC epoxy 
is non-toxic when cured and has been U.S.D.A. approved. 
It should be understood that only the polished exposed end of the antimony 
electrode is used in the monitoring process. The rest of the exposed sides 
are coated with this relatively rigid epoxy 15 although of course full 
length coverage is not essential. 
I have found that four different stages of applying the epoxy 15 may be 
used efficiently. 
(1) Epoxy applied to cover 100% of the electrode and the solder up to but 
not including the silver wire attached thereto, leaving the polished face 
exposed. 
(2) Epoxy applied to cover 100% of the electrode only, once again with the 
exception of the polished end. 
(3) Epoxy applied to cover 75% of the antimony electrode with the polished 
face being exposed. 
(4) Epoxy applied to cover 100% of the antimony electrode and 75% of the 
solder, once again leaving the polished face exposed. 
The above are exemplary only and may of course be varied, once again 
depending upon design parameters. 
However, whichever degree of covering with the relatively rigid epoxy 15 is 
used, nevertheless it will be understood that any exposed surface of the 
electrode, excepting the polished tip or face, together with exposed 
solder and attached silver wire must be shielded electrically and this is 
accomplished by means of inserting the assembly into a length of treated, 
clear extruded TEFLON (T.M.) tubing such as Cole-Flex TT-250/22. AMS-3655. 
This tubing has an inside diameter of 0.027 inches with a wall thickness of 
0.010 inches and an outside diameter of 0.047 inches. However other 
dimensioned tubing may of course be utilized. 
The end of this tubing engaging around the antimony electrode portion of 
the assembly adjacent the polished end surface, must be sealed to the 
epoxy 15 in order to prevent contamination occurring between the tubing 
and the epoxy. Because of the difficulty of sealing TEFLON (T.M.) tubing, 
the end of the TEFLON (T.M.) tubing must be neutralized before adhesively 
securing same to the electrode. 
The exposed inner and outer surfaces of the TEFLON (T.M.) tubing 
approximately 3 to 4 inches back from the end to be attached, are treated 
as follows in small individual beakers although other containers may of 
course be used. 
(a) Flush and dip in Ethyl Acetate, then air dry (Fisher Scientific 
E14573952); 
(b) Flush and dip into a solution until the tubing turns dark brown 
(immersed for 50 to 60 seconds) and then air dry (Chemgrip Treating Agent 
by Chemplast Inc.); 
(c) Clean and flush in Acetate; 
(d) Flush and rinse in a solution of hot water and detergent; 
(e) Air dry. 
In the final assembly of the electrode, the silver wire with the antimony 
electrode attached by solder, is pulled through one end of the treated 
TEFLON (T.M.) tubing. A small quantity of 0151 Hysal Epoxy or other 
equivalent adhesive is applied to the end tip of the TEFLON (T.M.) tubing 
that has been treated, just before it is finally pulled into position with 
this treated end substantially flush with the exposed polished end of the 
electrode as clearly shown in FIG. 1. The completed unit is then left to 
air dry at room temperature of 70.degree. F., for approximately 12 hours. 
FIG. 4 shows a chart which indicates: 
(a) testing of an antimony electrode before grinding. 
(b) the test after grinding to a concave shape; 
(c) and testing after two polished finishes as hereinbefore described. 
Two pH sources were used, namely, pH3 and pH7 and four tests were taken 
with the results shown on the chart, it being understood that the 
electrodes were cleaned between each use. It will be noted that the highly 
polished electrodes (c) prove far superior to the conventional electrode 
shown in (a). 
Conventional electrodes do not have a highly polished convex exposed face 
but a rough surface or sometimes, a ground convex shape which is not 
polished so that variations in pH measurements occur. 
Some conventional electrodes use a relatively hard epoxy which covers all 
of the antimony electrode with the exception of the exposed face, all of 
the solder and a small portion of the silver wire attached to the 
electrode by the solder. Often, the balance of the silver wire has also 
been epoxied and shielded with a softer epoxy which is also subject to 
breaking when bent. 
The present assembly overcomes all of the disadvantages inherent with 
conventional assemblies and in addition provides a highly polished exposed 
antimony electrode surface which enables extremely accurate measurements 
of pH to be taken as shown in (c) on the chart shown in FIG. 4. 
Dealing next with FIGS. 5 through 9, FIG. 5 illustrates a reference 
electrode for use with the electrode assembly described and illustrated in 
FIGS. 1 through 3. 
It consists of a length of plastic tubing 17 which is preferably formed 
from an intramedic nonradiopaque polyethylene material being sealed at one 
end 18 by means of a connector such as a tip jack 19 to which may be 
connected a connecting conductor or cable (not illustrated). 
Situated within the tubing is a length of silver wire 20 sealable and 
operatively connected to the tip jack 19 by one end thereof and sealed by 
an epoxy resin seal 21 surrounding the first portion of the silver wire 
20. 
The silver wire is coated with silver chloride by dipping the wire into a 
supply of molten silver chloride powder thus producing what is known as a 
silver silver chloride conductor. 
Surrounding this conductor and filling the tube 17 is an electrolyte in the 
form of a gel formed from potassium or sodium chloride with potassium 
chloride being the preferred electrolyte. Redux Cream manufactured by 
Hewlitt Packard is a suitable electrolytic gel. Reference character 22 
illustrates this electrolyte within the tube 17 and it should be noted 
that the electrode 20 terminates spaced from the other end 23 of the tube 
17. 
This said other end is sealed by means of a plug 24 frictionally and 
sealably engaged therein with the distal end 25 extending from the end 23 
of the tube and this plug is saturated in an electrolyte so that it is 
electrolytically connected between the distal end 25 and the gel 22 within 
the tube 17. 
In the present embodiment, a wooden plug is utilized manufactured from pine 
which is saturated in a concentrated solution of potassium or sodium 
chloride and a mixture of distilled water for a period of approximately 18 
days to insure complete impregnation of the plug with the electrolyte 
solution. 
This enables the electrodes 20 to indicate the pH contacted by the distal 
end portion 25 of the plug 24 and to convey same via the cable extending 
from the tip jack 19 to suitable instrumentation (not illustrated). 
The advantages over conventional reference electrodes is that the liquid 
junction between the sample and the electrolyte is completely isolated so 
that contamination of the sample with the electrolyte during measurements 
does not take place. Conventionally, such electrolytes utilize a drip 
method to insure the necessary conduction whereas the present reference 
electrode is extremely rugged and does not contaminate and can be used in 
various environments where pH measurements are required without 
contamination. 
It will of course be appreciated that it is necessary to maintain the plug 
24 in the electrolytic conducting relationship with the electolyte 22 
within the tubing and reference should be made to FIG. 6 which shows a 
storage tube 26 consisting of a length of polyethylene tubing or the like 
having a plug 27 at one end thereof sealing off this one end. 
This tube is filled with an electrolyte gel solution including either 
potassium or sodium chloride and in this connection a vent hole 28 may be 
formed through the wall of the tube adjacent plug 27 to ensure complete 
filling of the tube. This hole or aperture 28 may be sealed with a small 
rubber band 29 or the equivalent thereof. When storing the reference 
electrode or transporting same, the reference electrode is inserted into 
the tube with the distal end 25 of the plug remaining completely immersed 
within the electrolyte solution and maintaining the saturation of the plug 
for efficient conductivity between the distal end 25 and the electrolytes 
22 within the reference electrode assembly. 
When ready for use, the reference electrode assembly is withdrawn from the 
tube 26, the tip 25 is dried and dipped in distilled water and then dried 
again and is then ready for use. 
It should be noted that the tip jack 19 is soldered to the end of the 
silver silver chloride wire or electrode and is then frictionally engaged 
within the end of the tubing 17. It is sealed on the outside and then 
treated with an accelerator which increases gap filling abilities and 
minimizes adhesive migration from the bond areas. The electrolyte cream or 
gel is then injected into the tubing 17 from the other end thereof to 
overflowing and then the saturated plug 24 is forced into the end of the 
tubing and secured by an epoxy resin or the like around the area where the 
peg extends from the end of the tubing. Once again a bonding and 
accelerator may be applied to prevent adhesive migration. 
FIGS. 7 and 8 show a reference electrode in combination with the antimony 
electrode assembly previously described and, where applicable, similar 
reference characters have been used. 
The tube 17 is of similar construction to that described in FIG. 5 and the 
electrolytically saturated plug 24A is similar with the exception that it 
is drilled longitudinally to sealably receive the distal end of the 
electrode assembly illustrated in FIG. 1 with the exposed tip 10A of the 
antimony electrode extending beyond the distal end 25A of the plug 24A as 
clearly illustrated. 
The electrode wire 12 encased within the TEFLON (T.M.) tubing 16 extends 
through the gel 22 within the tubing parallel to the reference electrode 
20 which is also within the tubing 17. The plastic tubing 16 and wire 12 
of the antimony electrode extend through a plug 30 together with the 
conductor 31 of the reference electrode and a plastic housing or piece of 
tubing 32 extends over the end 18 of the tube 17 where the two conductors 
emerge. The end of the antimony electrode extending through the saturated 
plug 24A is sealed by epoxy as is the plug 24A where it engages the end 22 
of the tubing. 
The other end of the tubing is also sealed with epoxy as hereinbefore 
described with reference to FIG. 5 and the two wires may then be 
terminated in a conventional cable end connector (not illustrated). Once 
again, the plug 24A is saturated with an electrolyte and the conductivity 
and saturation is maintained by storing same in a storage tube as 
illustrated in FIG. 6 and previously described. 
Finally, reference should be made to FIG. 9 which utilizes the combination 
reference and antimony electrode assembly of FIG. 7 with the exception 
that the conductors 12 and 31 are relatively long and covered with an 
intramedic tubing 33, the end 34 of which is sealably engaged over the end 
18 of the tube 17 and with the termination of the conductors being 
operatively connectible to the necessary meter (not illustrated) with a 
relatively long length of tubing covering the conductors, the device is 
suitable particularly for esophageal examination. 
Again the combination electrode should of course be stored in a storage 
tube as in FIG. 6, when not in use. 
Since various modifications can be made in my invention as hereinabove 
described, and many apparently widely different embodiments of same made 
within the spirit and scope of the claims without departing from such 
spirit and scope, it is intended that all matter contained in the 
accompanying specification shall be interpreted as illustrative only and 
not in a limiting sense.