Chemistry: molecular biology and microbiology – Apparatus – Including measuring or testing
Reexamination Certificate
2001-03-27
2004-03-23
Naff, David M. (Department: 1651)
Chemistry: molecular biology and microbiology
Apparatus
Including measuring or testing
C435S004000, C435S176000, C435S177000, C435S817000
Reexamination Certificate
active
06709856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a measuring device for a liquid sample and a method for measuring the liquid sample, where a sensor comprising an enzyme layer is used to determine a particular component contained in a liquid sample introduced from a liquid sample inlet channel.
2. Description of the Prior Art
For measuring a component in a liquid sample such as blood and case fluid, there has been widely employed an approach that a collected liquid sample such as blood and case fluid is directly introduced into a sensor unit, it is measured with the sensor and then the liquid sample is discharged. In such a measuring procedure, a particular component is measured during the liquid sample as a continuous flow passes over the sensor surface.
JP-A 10-339716 has disclosed an example of such a measuring device for a liquid sample.
FIG. 10
shows the structure of the device. This device consists of a case
48
, a sensor platform
47
, a measuring circuit
61
, a data processor
62
and a data display
63
. The case
48
comprises a standard liquid inlet
41
, a standard liquid outlet
42
, a sample inlet
44
and a sample outlet
43
. The sensor platform
47
consists of a screw
45
, a stopper
49
, a sensor
46
, and two liquid inlet channels
50
a
and
50
b
. The stopper
49
and the sensor
46
are fixed on the platform
47
with the screw
45
. A signal detected by the sensor
46
is transmitted via an electric cable
53
through the measuring circuit
61
, the data processor
62
and finally to the data display
62
where the signal is displayed as a measured value. The sensor platform
47
and the case
48
are placed in a manner that they are mutually slidable.
The sensor
46
in the liquid inlet channels
50
a
and
50
b
is removably fixed inside of the liquid inlet channel
50
a
by the sensor platform
47
. Here, the sensor is fixed such that the exposed surface of the sensor
46
to the liquid inlet channel
50
a
is placed in the substantially same plane as, preferably slightly inner than, the inner surface of the liquid inlet channel
50
a
. Thus, in the liquid inlet channel
50
a
, a standard or sample liquid may not be disturbed or remain and therefore may be quickly charged and discharged.
The above prior art have advantages that a small amount of liquid sample may be measured and that since a sensor unit is removable, a worn sensor may be replaced with a new one. Furthermore, despite a simple structure, such a device may achieve good measurement accuracy. However, a measuring device with a simple structure has been recently required to achieve performance comparable to a larger device, and there is a room for improving measurement accuracy and stability in a measured value.
In a device measuring a liquid sample by introducing it to a sensor unit via a channel, particularly a device measuring a liquid sample as a continuous flow during it passes over the sensor surface, the sensor is generally placed on the side wall of the channel so that the liquid sample flows in parallel to a plane containing the sensor surface. The above-mentioned application has disclosed an example of a device having such a configuration.
However, when a sensor has an enzyme layer in the upper part of its electrode in a device having such a configuration, it may cause reduced measurement accuracy, unstable measured value and reduced response.
In a sensor comprising an enzyme layer, a component to be measured is diffused in the enzyme layer and is subject to an enzyme reaction in the enzyme layer to generate a current in an electrode which gives a measured value. In such a sensor, the amount of a chemical species derived from the component to be measured which reaches the electrode depends on a concentration of the component to be measured near the sensor surface. However, when the liquid sample moves to a direction parallel to the sensor surface, the concentration of the component to be measured may tend to vary near the sensor surface, leading to reduced measurement accuracy and unstable measured value.
When placing the sensor on the side wall of the channel, it is difficult to place the sensor such that its surface is in the completely same plane as that of the inner wall of the channel. Resultantly, a slight misalignment may lead to protrusion or depression of the sensor surface. Such a shape may cause disturbance of liquid sample flow near the sensor surface where the concentration of the component to be measured may, thus, vary, leading to reduced measurement accuracy and unstable measured value. Furthermore, in a second measurement after the first measurement and washing, a dead space which may be formed near the sensor may frequently cause reduced measurement accuracy, unstable measured value and reduced response due to residual measured liquid sample or washing. In particular, when using a biological fluid as a liquid sample, the amount of the sample is so small that a dead space formed may give significant influence. In this respect, the above-mentioned JP-A 10-339716 has descried that protrusion or depression of a sensor surface may reduce measurement sensitivity.
In addition, in a measuring device where a sensor is removable from its installation site, its structure may cause misalignment of the sensor surface to the inner wall of the channel. Furthermore, whenever replacing a sensor, precise alignment is required so that sensor replacement becomes difficult work. Thus, problems due to misalignment between the inner wall of the channel and the sensor surface becomes more prominent for a measuring device in which a sensor is removable.
On the other hand, for example, the inner structure of the channel may be improved for solving the above problems. However, such an improvement may lead to a complex device structure, thus make sensor replacement difficult and make mass production or cost reduction of the device difficult.
In addition, in a measuring device according to the prior art, a measured value may become unstable when measuring a biological fluid as a liquid sample repeatedly or continuously, which may be due to adhesion of contaminants such as proteins contained in the biological fluid on the inner wall of the channel. In a measuring device according to the prior art, there is also a room for improvement in this respect.
In view of the above problems, an object of this invention is to provide a device with an enzyme layer for measuring a liquid sample and a method for measuring the liquid sample, which may achieve excellent measurement accuracy, stable measurement sensitivity and quick response as well as prevention of sensitivity reduction in repeated or continuous measurement. In particular, an objective of this invention is to solve the above problems in a measuring device in which a sensor unit is removable.
SUMMARY OF THE INVENTION
This invention provides a device for measuring a liquid sample comprising:
a sensor for measuring a component in the liquid sample;
a liquid sample inlet channel for feeding the liquid sample to the sensor surface; and
a liquid sample outlet channel for discharging the liquid sample from the sensor surface,
the sensor having an electrode and an enzyme layer in the upper part of the electrode,
the liquid sample inlet channel being placed at an angle to the sensor surface, and one opening end of the liquid sample inlet channel being placed in the vicinity of the sensor surface.
As described above, in a conventional measuring device generally having a style that a sensor is mounted on the side wall of a channel, there has been problems of, for example, reduced measurement accuracy, unstable measured value and reduced response when using a sensor comprising an enzyme layer. To solve the problem, this invention employs a configuration that a liquid sample inlet channel is placed at an angle to a sensor surface and one opening end of the liquid sample inlet channel is placed in the vicinity of the sensor surface, whereby a flow condition of the liquid sample suitable to measurement near the sensor s
Kohashi Hiroshi
Matsumoto Toru
Matsumoto Yasuyoshi
Naff David M.
NEC Corporation
Scully Scott Murphy & Presser
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