Ion sensor and ion sensor plate

Details Ion sensor and ion sensor plate Ion sensor and ion sensor plate

1998-12-28

2001-12-11

Tung, T. (Department: 1744)

Chemistry: electrical and wave energy

Apparatus

Electrolytic

C204S418000, C204S435000

Reexamination Certificate

active

06328866

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an ion sensor for various kinds of ion that can be employed in the examination of blood, etc. This invention also relates to a disposable simplified ion sensor plate partially constituting the ion sensor.
The ion sensor is generally formed of a structure comprising a silver/silver halide (Ag/AgX) electrode wherein a silver halide layer is deposited on a silver layer, an inner electrolyte solution, and an ion sensitive membrane (ISM). Since an inner electrolyte solution is employed in the ion sensor as described above, a vessel for accommodating the inner electrolyte solution is required. As a result, it has been very difficult to miniaturize the ion sensor or to make the ion sensor into a disposable type.
Under the circumstances, there has been developed a disposable simplified ion sensor plate for examining a blood sample, etc., and some kinds of it have been actually proposed.
As one example of such proposals, there has been known a differential type multi-ion sensor wherein a multi-ion sensor plate is connected with a measuring circuit thereby to measure concurrently the concentrations of many different kinds of ion. This multi-ion sensor is constructed as shown in FIG.
2
. Namely, it comprises a multi-ion sensor plate main body
5
provided with 5 groups of electrode pairs, each group consisting of a test liquid-measuring electrode
2
a
and a reference electrode
2
b,
which are formed on a glass-epoxy resin substrate
1
by a process wherein copper electrodes are formed in advance by means of an etching process and then subjected to an electrolytic silver plating thereby to form a silver layer thereon, and with silver chloride layers
4
a
and
4
b
deposited on the silver layer formed on one end portion of each test liquid-measuring electrode
2
a
as well as on the silver layer formed on one end portion of each reference electrode
2
b
which faces the aforementioned one end portion of the test liquid-measuring electrode
2
a,
the other end portions of these electrodes
2
a
and
2
b
which are remote from the aforementioned one end portions being constituted as an outer electrode, respectively.
The multi-ion sensor further comprises a channel body
9
which is designed to be contactingly superimposed on the multi-ion sensor plate main body
5
and consists of a polyester film provided with through-holes
6
a
to
6
e
and
6
′a
to
6
′e
communicating with the silver chloride layers
4
a
and
4
b
of each group of an electrode pair, respectively, with an elongated hole constituting a liquid junction portion 7 which is formed to coincide with the forward ends of two channels of the upper cell to be explained hereinafter and is designed to allow a test liquid to be contacted with the reference liquid, and with through-holes
8
a
and
8
b
communicating respectively with the electrodes
2
a
and
2
b
of each group of an electrode pair.
Various kinds of ion-sensitive film-forming solution containing various kinds of ion-sensitive material such as a large cyclic compound called ionophore or an ion-exchange resin are individually applied through these through-holes
6
a
to
6
e
and
6
′a
to
6
′e
to the surfaces of silver chloride layers
4
a
and
4
b,
and then dried to form five kinds of different ion-sensitive films on the surfaces of silver chloride layers
4
a
and
4
b.
The combined body consisting of this multi-ion sensor plate main body
5
and channel body
9
is then fitted in the recessed portions
10
a
and
10
b
of a lower cell
10
formed of a transparent acrylic resin plate. The resultant lower cell
10
is subsequently superimposed thereon with an upper cell
12
formed of a transparent acrylic resin via a pressure sensitive adhesive double coated tape so as to bond the lower cell
10
and the upper cell
12
to each other, thus packaging the aforementioned combined body.
The upper cell
12
is provided on the reverse surface thereof with a couple of channels
13
and
14
which are partitioned by a barrier wall and communicated with the through-holes
6
a
to
6
e
and
6
′a
to
6
′e
, respectively, each channel being formed of a U-shaped groove. A test liquid inlet portion
15
and a reference liquid inlet portion
16
are formed to communicate respectively with one end of the channels
13
and
14
. A pair of air vent grooves
13
a
and
14
a
each being formed of a U-shaped groove of small width and bent into an L-shape are symmetrically disposed to communicate with the other end of the channels
13
and
14
, respectively. The distal ends of these air vent grooves
13
a
and
14
a
are communicated with vertical passageways
13
b
and
14
b
formed at the forward end portions of the test liquid inlet portion
15
and the reference liquid inlet portion
16
, respectively.
The upper cell
12
is further provided with terminal-insertion holes
18
a
and
18
b
for allowing the terminals of the measuring apparatus (not shown) to be inserted therein, the location of these terminal-insertion holes
18
a
and
18
b
coinciding with the exposed terminals of the outer electrodes of the test liquid-measuring electrode
2
a
and the reference electrode
2
b.
When this multi-ion sensor plate is to be employed, a test liquid and a reference liquid are introduced by making use of a syringe, etc. into the test liquid inlet portion
15
and the reference liquid inlet portion
16
, respectively. As a result, these liquids are supplied through the channels
13
and
14
to the ion-selective electrodes in the through-holes
6
a
to
6
e
and
6
′a
to
6
′e
, respectively, and at the same time, the test liquid is contacted with the reference liquid at the liquid junction portion
7
. Under this condition, the terminals of measuring apparatus are inserted into the terminal-insertion holes
18
a
and
18
b
so as to be contacted with the outer electrodes respectively, thereby measuring the ionic components of the test liquid. As a result, the concentrations of 5 kinds of ion can be measured simultaneously with a single injection of these test liquid and reference liquid.
Even in the case where an ion-sensitive film is directly formed on the surface of Ag/AgX electrode as described above, the electric potential to be generated can be determined by the dissociation equilibrium represented by the formula: AgX&rlarr2;Ag
+
+X
−
as in the case of an the ordinary ion sensor. However, when a composition comprising polyvinyl chloride type resin and a plasticizer thereof is employed as an ion-sensitive film, the AgX constituting the underlying layer is dissolved mainly by the solubilizing power of this plasticizer, i.e. this ion-sensitive film is capable of functioning in the same manner as that of the inner electrolytic solution employed in the ordinary ion sensor.
In this case, the dissolving degree of the AgX layer can be controlled in a certain degree by the grain size and surface roughness of the AgX layer, and the electric potential to be generated can be controlled within a relatively limited range as made clear in our previous patent applications (Japanese Patent Applications H/1-135728 and H/1-222909).
By the way, in the structure where an ion sensitive membrane is directly formed on the surface of silver chloride layer without providing an inner aqueous electrolyte solution layer as mentioned above, the ion sensitive layer is formed by a process wherein a solution of a mixture containing a sensitive material or so-called ionophore which is selectively sensitive to an ion to be detected, and a salt such as an anion scavenger for eliminating the interference of anion originating from a test liquid or a reference liquid is prepared at first, and then coated on the surface of a matrix formed of polyvinyl chloride type resin for instance. However, in order to ensure the flexibility of this coated film so as to prevent the coated film from being peeled off from an underlying layer or from being cracked, a plasticizer is concurrently mixed into the

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