Optics: measuring and testing – Refraction testing – Differential
Reexamination Certificate
2000-03-09
2001-09-25
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Refraction testing
Differential
Reexamination Certificate
active
06295125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical field
The present invention relates to a differential refractive index detector and a liquid chromatograph equipped with the same.
More specifically, the present invention relates to a differential refractive index detector which can automatically perform the processing from the eluent purge operation of reference cell at the start of operation until the stability confirming operation by judging whether or not the detector was stabilized in an analysis capable condition, thereby enabling more efficient analysis work, and also relates to a liquid chromatograph equipped with the detector.
2. Related Art
FIG. 5
is a block diagram showing the outline of a conventional differential refractive index detector for a liquid chromatograph. As shown in
FIG. 5
, a conventional differential refractive index detector comprises two cells
11
and
12
consisting of a reference cell
11
for filling with or passage of a reference solution and a sample cell
12
through which a solution containing a sample is passed. These cells
11
and
12
are disposed such that their slant faces oppose each other. The sample cell
12
is connected by an eluent inlet line
14
for introducing an eluent eluted from a separation column
13
and by a sample cell outlet line
15
. The reference cell
11
is connected by a reference cell inlet line
16
communicating with the sample cell outlet line
15
and by a reference cell outlet line
17
.
At the connection between the reference cell outlet line
17
and a line
18
externally extended from the connection of the sample outlet line
15
with the reference cell inlet line
16
, a three-way solenoid valve
19
is provided. To this three-way solenoid valve
19
, an eluent outlet line
20
for discharging the eluent outside is connected. By intermittently switching over the three-way solenoid valve
19
on demand, the eluent which was flowed out from the sample cell
12
can be intermittently allowed to flow into the reference cell
11
.
On one side with respect to the reference cell
11
and the sample cell
12
, a light source
21
for irradiating a measuring beam is provided, and on the other side, a reflector
22
for reflecting the measuring beam transmitted through these cells
11
and
12
is provided. Furthermore, in the vicinity of the light source
21
, a photoreceptor device for detecting the displacement of the measuring beam accompanying the difference in the refractive index of the eluent in the two cells
11
and
12
is provided.
The light source
21
, the photoreceptor device
23
and the three-way solenoid valve
19
converge at a signal processing part
24
. The signal processing part
24
has a function of outputting the difference in refractive index of the eluent into two cells
11
and
12
as an electric signal based on a signal sent from the photoreceptor device
23
and at the same time, controlling the driving of three-way solenoid valve
19
and the driving of light source
21
based on an operation signal sent from the outside.
In the conventional differential refractive index detector, electric power is charged and then start-up is initiated by an input unit not shown, as a result, the three-way solenoid valve
19
is actuated through the signal processing part
24
to bring a state such that the piping
18
is closed and the reference cell outlet line
17
communicates with the eluent outlet line
20
.
Subsequently, the following operations are performed in sequence.
(1) Initial Solution Purge Operation
This is an operation of purging the inside of the reference cell
11
with an eluent at the start of operation of the differential refractive index detector.
(2) Stabilizing Solution Purge Operation
This is an operation of confirming whether factors other than the change of refractive index are in a stabilized condition by continuously passing an eluent which has flowed out from the sample cell
12
, through the reference cell
11
.
(3) Stability Confirming Operation
This is an operation of confirming whether or not the differential refractive index detector has stabilized in an analysis capable condition while keeping the flow passage in an analyzable condition by stopping the flow of eluent into the reference cell
11
.
Through these operations, the differential refractive index detector can be stabilized in an analysis capable condition.
In the case where a conventional differential refractive index detector is used as a liquid chromatograph detector, the change in the refractive index of the eluent causes a serious problem. The refractive index of the eluent changes not only with the elution of a sample but also by the staining of eluent itself, the dissolved gas concentration, the temperature and the like. Accordingly, in order to stabilize the differential refractive index detector at the start of operation, unlike an ultraviolet absorbance detector which is a general liquid chromatograph detector, an initial solution purge operation of purging the referential cell
1
with a solution at the start of operation and subsequently stabilizing the solution purge operation, and stability confirming operation of monitoring the output signal (chromatogram) over a relatively long period of time until a stable condition is reached are necessary. Thus, much labor and a long period of time are disadvantageously required.
Furthermore, the judgement that the differential refractive index detector has reached a stable condition is made by intuition in many cases and greatly depends on the experience and skill of the judging person. This naturally brings about great personal errors in the judgement of stable condition. Depending on the case, the condition may be excessively stable or may be deficient in stability. Thus, this intuitive judgement is disadvantageous in that an efficient operation cannot be attained.
SUMMARY OF THE INVENTION
The present invention was developed in order to solve the problems described above. It is an object of the present invention to provide a differential refractive index detector in which the processing from an initial solution purge operation of intermittently introducing an eluent into a referential cell until a stability confirming operation of confirming that the differential refractive index detector has stabilized in an analysis capable condition are automated, thereby eliminating fears for personal errors in the judgement of stable condition and enabling a highly efficient analysis operation, and also to provide a liquid chromatograph equipped with the detector.
As a result of extensive investigations, the present inventors have found that the above-described objects can be attained by using a differential refractive index detector described below and a liquid chromatograph equipped with the detector. The present invention has been accomplished based on this finding.
More specifically, the present invention relates to the following matters.
The differential refractive index detector of the present invention, provided with a reference cell for filling or passing a reference solution, a sample cell for passing a solution containing a sample, a light source for irradiating light on the two cells, a detecting part for detecting light transmitted through the respective cells, and a signal processing part for applying a predetermined processing to the output signal sent from the detecting part, is characterized by comprising means for sequentially performing an initial solution purge operation of purging the sample cell and the reference cell with an eluent by passing the eluent through the cells at the start of operation of the detector, a stabilizing solution purge operation of allowing the eluent purge of the sample cell and the reference cell to proceed and at the same time, confirming the stable condition thereof, and a stability confirming operation of confirming whether or not the detector has stabilized in an analysis capable condition by passing the eluent only through the sample cell, and means for announcing that the detector has stabilized in the analysi
Inoue Saburo
Nogami Yukio
Tokieda Tsunemi
Pham Hoa Q.
Showa Denko K.K.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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