Chemistry: molecular biology and microbiology – Apparatus – Including measuring or testing
Reexamination Certificate
2001-08-23
2002-07-30
Redding, David A. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Including measuring or testing
C435S287100, C156S153000
Reexamination Certificate
active
06426212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates: generally to biological conductivity testing cells possessing a substantially cylindrical structure; more particularly to biological conductivity testing cells possessing a substantially cylindrical structure with two opposed Pt alloy electrodes disposed upon either end; and most specifically to biological conductivity testing cells possessing a substantially cylindrical structure with two opposed Pt alloy electrodes disposed upon either end intended for passage of a weak alternating current therethrough for the obtainment of impedance measurements.
2. Prior Art
Biological conductivity testing cells possessing a substantially cylindrical structure with two opposed Pt alloy electrodes disposed upon either end intended for passage of a weak alternating current therethrough are considered to be well known. With regard to the present innovation the prior art is considered to be restricted to simple deposition of Pt alloy upon equivalent areas with regard to either end including interior, exterior, and end surfaces.
FIG. 1
depicts a conventional conductivity testing cell
10
made of a glass cylinder
11
and two opposed electrodes
12
between which a weak alternating current in passed through a biological sample held therein for measuring changes in impedance associated with metabolic activity inclusive of cell division and genetic replication.
FIG. 2
depicts in detail an end of the conventional conductivity testing cell
10
depicted in
FIG. 1
inclusive of a portion of the glass cylinder
11
and an electrode
12
with exposed interior and exterior surfaces
21
,
20
resulting from the simple deposition of the Pt alloy which are both offset with respect to the adjacent exposed glass interior and exterior surfaces
15
,
17
, and necessarily present an exposed edge
22
of the electrode
12
which is subject to shear. It is further seen that the covered glass interior and exterior surfaces
15
,
17
under the electrode
12
are the same as the adjacent exposed glass surfaces
15
,
17
.
Conventional conductivity testing cells
10
made of a glass cylinder
11
possessing two opposed electrodes
12
between which a weak alternating current is passed through a biological sample held therein must be autoclaved between tests in order to assure sterility prior to introduction of a new biological sample. Repeated autoclaving results in separation of the Pt alloy deposition comprising the electrodes
12
from the underlying glass interior and exterior surfaces
15
,
17
. Serious deterioration of the electrode
12
resulting from shear during autoclaving is typically experienced after only three cycles of using the testing cell
10
.
The electrodes
12
must be Pt alloy because platinum possesses unique characteristics with regard to electro-chemical activity: platinum, alone among all the elements, acts as a pure catalyst for electro-chemical activity without loss of material and without other undesired activity. It is noted that the portions of the electrodes
12
disposed interiorly in conventional conductivity testing cells
10
comprised of a glass cylinder
11
as depicted in
FIG. 1
extend inwardly much further than the portions of the electrodes
12
disposed exteriorly. This is because the exterior portion makes electrical contact with a metal conductor while the interior portion facilitates the conductance of electrical current through a water based biological sample and a greater surface area is required to support the conductance of the electrical current across the interface with this inherently less conductive medium.
Statement of Need
With a current cost of approximately twice that of gold platinum is considered relatively expensive. Platinum has many industrial uses including laboratory glassware and catalytic converters necessary to NO
x
reduction from internal combustion engine exhaust. It is not anticipated that the cost of platinum will be greatly reduced in near future owing to anticipated demand. While the amount of platinum in the Pt alloy deposition upon a conventional biological conductivity testing cell is measured in grams a degraded electrode
12
cannot be repaired without return of the testing cell for complete removal and redeposition of the Pt alloy and conductivity test cells
10
are hence routinely discarded after deterioration of one of the electrodes
12
.
Therefore, the entire cost of the conductivity test cell
10
must be amortized over an average of approximately three tests, including the cost of manufacturing the glass cylinder
11
, the platinum in the Pt alloy deposition, the process of deposition, transportation, and all other expenses associated with getting a product to market. While the cost of replacing a conductivity test cell
10
after an average of three tests may be acceptable in research it is recognized that this cost is inhibitive of clinical usage wherein millions of tests annually are anticipated. A need is hence discerned for a means of increasing the number of tests a biological conductivity test cell
10
can be utilized prior to deterioration of the electrodes
12
.
SUMMARY OF THE INVENTION
Objects of the Invention
The encompassing object of the principles relating to the present invention is a biological conductivity testing cell with a platinum alloy electrode upon each of two opposed ends of a glass cylinder which is relatively unaffected by autoclaving.
A first auxiliary object of the principles relating to the present invention is the provision of a chemically pure surface upon end surfaces of a glass cylinder intended for deposition of platinum alloy thereby eliminating contamination.
A second auxiliary object of the principles relating to the present invention is the provision of a uniform surface roughness upon end surfaces of a glass cylinder intended for deposition of platinum alloy for resisting shear.
A third auxiliary object of the principles relating to the present invention is the provision of platinum alloy upon the two opposed ends of a glass cylinder wholly within the overall cylindrical cell dimensions thereby eliminating all exposed edges of the deposition.
A fourth auxiliary object of the principles relating to the present invention is the provision of radially and axially uniform etching upon end surfaces of a glass cylinder intended for deposition of platinum alloy for resisting shear.
A fifth auxiliary object of the principles relating to the present invention is the provision of evenly spaced grooves annular upon end surfaces of a glass cylinder intended for deposition of platinum alloy for resisting shear.
Ancillary objects of the principles relating to the present invention include the preservation of desired electrical characteristics of the electrodes comprised of the deposition of platinum alloy upon the end surfaces of a glass cylinder in use as a biological conductivity testing cell for the measurement of impedance of a weak alternating current passed through a biological sample contained therein and the utilization of a greater interior surface area relative the exterior surface area of each end of the glass cylinder for deposition of platinum alloy thereupon.
Principles Relating to the Present Invention
In achievement of the above stated objectives it is suggested that removal of glass surface material by abrasion from the end surface areas of a glass cylinder intended for deposition of platinum alloy prior to deposition be effected. If the entire surface area intended for deposition thereupon is abraded with a chemically inert abrading material immediately prior to deposition of the platinum alloy a chemically pure, virgin, surface is obtained and all potential contaminates which could later cause separation eliminated.
Utilization of an appropriate abrasion also achieves a uniform surface roughness also provides resistance to shear. With a uniform removal of glass surface material from the entire area intended for platinum deposition to a depth equivalent to the thickness of the coating deposite
Gibson Peter
Redding David A.
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