JP2012068024A - Differential refractometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of the concentration unevenness of a sample solution in a sample cell occurred due to the shape of the sample cell on measurement.SOLUTION: A flow cell of a differential refractometer comprises a partition wall 2a inclined with respect to the optical axis of a measuring beam, a reference cell 3a partitioned by the partition wall 2a, and a sample cell 3b. The reference cell 3a and the sample cell 3b have the same triangle cross section and a surface vertical to the optical axis of the measuring beam. Each of both the cells 3a and 3b comprises inlets 22a and 24a and outlets 22b and 24b, respectively, near the acute angle part between a surface vertical to the optical axis of the measuring beam of the partition wall 2a and the partition wall 2a.

Description

  The present invention relates to a differential refractometer used as a detector for detecting a sample component in an analyzer such as a liquid chromatograph.

  The differential refractometer includes a flow cell composed of two cells separated by a partition inclined with respect to the optical axis of the measurement light. One cell of the flow cell is a sample cell for circulating the sample solution, and the other cell is a reference cell for circulating the reference solution. Furthermore, the measurement light refracted through the flow cell is received by the light receiving element that receives the measurement light, and the measurement light is irradiated to the flow cell through the slit, the measurement light from the flow cell is guided to the light receiving element, An optical system for forming an image is provided.

  In the differential refractometer, when the sample component passes through the sample cell of the flow cell, the refractive index in the sample cell changes, thereby changing the path of the measurement light passing through the flow cell and forming an image on the light receiving element. Since the slit image is displaced, by detecting the displacement amount, it is possible to detect a change in the refractive index of the sample solution and to detect the sample component passing through the sample cell (see Patent Document 1).

6A and 6B are diagrams showing an example of a flow cell of a conventional differential refractometer, where FIG. 6A is a cross-sectional view at an entrance portion, and FIG. 6B is a cross-sectional view at an exit portion.
The flow cell 30 includes two cells 32a and 32b separated by a partition wall 30a inclined with respect to the optical axis of the measurement light. The cells 32a and 32b have the same triangular cross section, and each cell 32a and 32b is provided with an inlet 34a and 36a and outlets 34b and 36b. The cell 32a is a reference cell for circulating the reference solution, and the cell 32b is a sample cell for circulating the sample solution.

JP 2008-32512 A

  Since the cross-sectional shape of the sample cell 32b is a triangle, a certain amount of unevenness occurs in the concentration of the sample solution flowing through the sample cell 32b. However, under the conventional measurement conditions, the influence of density unevenness on the measurement has been negligibly small. In recent years, a differential refractometer has a demand for a low flow rate of a sample flowing in a sample cell. It was found that when the flow rate of the sample flowing in the sample cell 32b is set to a low flow rate, the density unevenness caused by the triangular cross section of the sample cell 32b increases, and accurate measurement cannot be performed due to the influence. Specifically, the concentration of the sample solution is highest at the central portion of the cross section and lower than that near the acute angle portion. If there is density unevenness in the measurement light passage region, the measurement light is refracted in the sample solution, and the position of the slit image of the measurement light imaged on the light receiving element deviates from the original position.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the influence of sample solution concentration unevenness caused by the shape of a sample cell on measurement.

  The differential refractometer according to the present invention includes a light source that emits measurement light, a sample cell having the same triangular cross-section and a plane perpendicular to the optical axis of the measurement light, and a reference cell with respect to the optical axis of the measurement light. Partitioned by inclined partition walls and symmetrically arranged with the partition walls as axes, the inlet and outlet of both cells are in the vicinity of an acute angle portion between the surface perpendicular to the partition wall measurement light and the partition walls with respect to the optical axis. A flow cell provided vertically, a light receiving element for receiving measurement light that has passed through the flow cell, and an optical system that guides the measurement light to the light receiving element after passing through the flow cell.

  4A and 4B are diagrams schematically showing the concentration distribution in the cross section of the flow cell. FIG. 4A is a flow cell of a conventional differential refractometer, and FIG. 4B is a flow cell of the differential refractometer of the present invention. In addition, the density | concentration area | region in FIG. 4 is shown schematically, and the value of each area | region is also an approximate value.

  As shown also in FIG. 6, in the conventional flow cell, since it is easy to make, the inlet and outlet of the fluid are at an acute angle portion between the plane parallel to the optical axis of the measurement light and the partition wall. It was provided in the vicinity perpendicular to the optical axis of the measurement light. As shown in FIG. 4 (A), the concentration distribution in this case is about 7 in the vicinity of the acute angle portion where the inlet and the outlet are provided, and the obtuse angle portion (here 90 degrees) is about 9, and the vicinity of the acute angle portion on the side opposite to the inlet and outlet is about 6. In this state, a region having a density of 10 and a region having a concentration of 6 exist in the central portion of the cell through which the measurement light passes, and the measurement light is refracted at the boundary between both regions. As a result, the measurement light is imaged on the light receiving element. Will deviate from its original position.

  In contrast to the above-described conventional example, in the present invention, the positions of the inlet and outlet of each cell are defined so that the density unevenness of the sample caused by the cross-sectional shape of the cell is reduced. That is, the entrance and the exit are arranged perpendicular to the measurement light at an acute angle portion between the surface perpendicular to the measurement light and the surface facing the partition wall. Specifically, in FIG. 4B, in the present invention, the inlet and the outlet are provided in the vicinity of the acute angle portion located on the opposite side to the acute angle portion where the conventional inlet and outlet are provided. As a result, the concentration distribution in the cell cross section indicates that the central portion of the highest concentration is 10, the vicinity of the acute angle portion where the inlet and the outlet are provided is about 7, the obtuse angle portion is about 9, and the opposite side of the inlet and the outlet. The vicinity of the acute angle portion is about 6, and the measurement light passing through the central portion passes through the region of density 10 and the region of 7. Therefore, the concentration unevenness of the sample solution in the measurement light passage region is smaller than in the conventional case, and the measurement light is less likely to be refracted in the sample solution, so that the measurement accuracy is improved.

It is a schematic block diagram which shows one Example of a differential refractometer. It is a figure which shows the structure of the flow cell of the Example, (A) is a cross-sectional view in an entrance part, (B) is a cross-sectional view in an exit part. It is a figure which shows the structure of the flow cell of the Example, (A) is a longitudinal cross-sectional view of a reference cell, (B) is a longitudinal cross-sectional view of a sample cell. It is a figure which shows typically the density | concentration distribution in the cross section of a flow cell, (A) is the flow cell of the conventional differential refractometer, (B) is the flow cell of the differential refractometer of the Example. It is a graph which shows an example of the measurement data of the time change of an output signal at the time of using the differential refractometer of the Example and the conventional differential refractometer on the same conditions. It is a figure which shows an example of the flow cell of the conventional differential refractometer, (A) is a cross-sectional view in an entrance part, (B) is a cross-sectional view in an exit part.

An embodiment of the differential refractometer will be described below. FIG. 1 is a schematic configuration diagram showing a differential refractometer of one embodiment.
The flow cell 2 is disposed on the optical axis of the measurement light 6 from the light source 4 incident through the slit 8. The flow cell 2 has two cells separated by a partition wall 2a. One cell is a sample cell for circulating the sample solution, and the other cell is a reference cell for circulating the reference solution.

  A lens 10 is disposed in front of the flow cell 2, and a mirror 12 that reflects light transmitted through the flow cell 2 is disposed behind. A light receiving element 16 is provided on the optical path of the measurement light reflected by the mirror 12, and the measurement light reflected by the mirror 12 and transmitted through the flow cell 2 is imaged on the light receiving element 16. A zero glass 14 for translating the slit image on the light receiving element 16 is disposed between the lens 10 and the light receiving element 16 on the optical path of the measurement light after reflection. An arithmetic processing unit 20 is connected to the light receiving element 16. The arithmetic processing unit 20 calculates the refractive index change of the flow cell 2 based on the output signal of the light receiving element 16. The slit 8, the lens 10, the mirror 12, and the zero glass 14 constitute an optical system for causing the measurement light 6 to enter the light receiving element 16.

  The light emitted from the light source 4 passes through the slit 8 to become the measurement light 6, passes through the lens 10, is applied to the flow cell 2, passes through the flow cell 2, and is reflected by the mirror 12. The reflected light from the mirror 12 passes through the flow cell 2 again and is imaged as a slit image on the light receiving element 16 by the lens 10. The light receiving surface of the light receiving element 16 is divided into two, and the slit image is formed so as to straddle each of the two divided areas of the light receiving element 16.

  2 and 3 are sectional views of the flow cell 2. 2 (A) is an inlet portion of the flow cell, and FIGS. 3 (A) and 3 (B) are cross-sectional views at the YY position, and FIG. 2 (B) is an outlet port portion of the flow cell, and FIGS. In B), it is a cross-sectional view in the ZZ position. 3A is a reference cell side of the flow cell, and FIGS. 2A and 2B are longitudinal sectional views at the WW position. FIG. 3B is a sample cell side of the flow cell, and FIGS. In (B), it is a longitudinal cross-sectional view in the XX position.

  The flow cell 2 partitions the two cells 3a and 3b by a partition wall 2a inclined with respect to the optical axis of the measurement light. In this embodiment, the partition wall 2a is inclined 45 ° with respect to the optical axis. The cell 3a is a reference cell for circulating the reference solution, and the cell 3b is a sample cell for circulating the sample solution. Both cells 3a, 3b have the same right triangle cross section and are arranged symmetrically with the partition wall 2a as an axis.

  The reference cell 3a includes an inlet 22a through which the reference solution flows in from a direction perpendicular to the measurement light, and an outlet 22b through which the reference solution flows out in a direction perpendicular to the measurement light. The reference cell 3a has a plane perpendicular to the optical axis of the measurement light. An entrance 22a and an exit 22b are provided in the partition 2a between the surface perpendicular to the optical axis of the measurement light of the partition 2a and the partition 2a.

  The sample cell 3b includes an inlet 24a through which the sample solution flows in from a direction perpendicular to the measurement light, and an outlet 24b through which the sample solution flows out in a direction perpendicular to the measurement light. The sample cell 3b has a surface perpendicular to the optical axis of the measurement light. An inlet 24a and an outlet 24b are provided in the vicinity of an acute angle portion between a surface perpendicular to the optical axis of the measurement light of the partition 2a and the partition 2a.

  The cross section of the flow cell 2 is, for example, a square having a side of 5 mm, and a reference cell 3a and a sample cell 3b having a cross section in which a square having a side of, for example, 2 mm is divided into two equal parts are arranged at the center. The measurement light is adjusted by the slit 8 so as to pass through the center of the reference cell 3a and the sample cell 3b.

  Since the inlets 22a and 24a and the outlets 22b and 24b of the reference cell 3a and the sample cell 3b are provided in the vicinity of the acute angle portion between the plane perpendicular to the measurement light of the partition 2a and the partition 2a, As described above, the concentration distribution in the cross section of the fluid flowing through each cell is in a state as shown in FIG. Thereby, the density unevenness in the region through which the measurement light passes is smaller than the conventional flow cell concentration distribution shown in FIG. 4A, and the amount of refraction of the measurement light in the same cell is reduced. Thereby, the shift of the position of the slit image formed on the light receiving element 16 is reduced, and the detection accuracy of the differential refractometer is improved.

  FIG. 5 is a graph showing an example of measurement data of the time change of the output signal from the light receiving element when the differential refractometer of the same embodiment and the conventional differential refractometer are used under the same conditions. The vertical axis represents the output signal intensity [μV], and the horizontal axis represents time [min]. In this graph, the signal waveform of the differential refractometer of the same embodiment is shown by a solid line, and the signal waveform of the conventional differential refractometer is shown by a broken line.

  In the conventional differential refractometer, a negative peak occurs in a time zone of 0 to 0.25 min. This is because the measurement light is refracted by the sample density unevenness caused by the cross-sectional shape of the sample cell, and the position of the measurement light imaged on the light receiving element 16 is deviated from the original position. On the other hand, in the differential refractometer of the example, the negative peak in the same time zone is small. This means that the positional deviation of the slit image formed on the light receiving element 16 is reduced because the density unevenness of the measurement light passage region in the cross section of the sample cell 3b is reduced.

2 flow cell 2a partition 3a reference cell 3b sample cell 4 light source 6 measurement light 8 slit 10 lens 12 mirror 14 zero glass 16 light receiving element 20 arithmetic processing unit 22a, 24a fluid inlet 22b, 24b fluid outlet

Claims (1)

A light source that emits measurement light;
A sample cell and a reference cell having the same triangular cross section and a plane perpendicular to the optical axis of the measurement light are separated by a partition that is inclined with respect to the optical axis of the measurement light, and are symmetrically arranged with the partition as an axis. A flow cell in which the inlet and outlet of both cells are provided perpendicular to the optical axis in the vicinity of an acute angle portion between the surface perpendicular to the measurement light of the partition and the partition;
A light receiving element for receiving measurement light that has passed through the flow cell;
An optical system that guides measurement light to the light receiving element after passing through the flow cell.

Images