JP4793413B2 - Differential refractive index detector - Google Patents

Description

  The present invention relates to a differential refractive index detector used as a detector in an analyzer such as a liquid chromatograph.

  The differential refractive index detector has two cells partitioned by a wall inclined with respect to the optical axis of the measurement light, a flow cell through which the sample solution passes and the other through which the reference solution passes, and is refracted by this flow cell. A light receiving element that receives the measurement light, and an optical system that irradiates the flow cell with the measurement light through the slit, guides the measurement light from the flow cell to the light receiving element, and forms an image of the slit on the light receiving element. A change in the refractive index of the sample solution is detected from the amount of displacement of the slit image on the light receiving element.

  FIG. 2 schematically shows an example of the differential refractive index detector. Light from the light source 8 becomes measurement light 12 through the slit 10, and is irradiated to the flow cell 16 through a lens 14 placed in front of the flow cell 16. The flow cell 16 includes two cells 20a and 20b separated by a wall 18. The cell 20a has a liquid inlet 22i and an outlet 22o, and the cell 20b has a liquid inlet 24i and an outlet 24o. A mirror 26 is disposed behind the flow cell 16 so that the measurement light transmitted through the flow cell 16 is reflected by the mirror 26 and passes through the flow cell 16 again. The reflected light from the mirror 26 that has passed through the flow cell 16 is formed as a slit image on the light receiving element 30 by the lens 14. In order to translate the slit image on the light receiving element 30, a zero glass 28 is disposed on the optical path of the measurement light. The zero glass 28 can be operated by a pulse motor 32 driven by a motor driving circuit 34 to translate the slit image on the light receiving element 30. A signal processing circuit 36 performs signal processing for obtaining a change in refractive index based on a detection signal from the light receiving element 30.

  In the conventional differential refractive index detector, as shown in FIG. 3A, the light received is divided into two parts 2-1 and 2-2 by a straight line 4 perpendicular to the moving direction (X direction) of the slit image 6. An element is used, and the displacement of the slit image 6 on the light receiving element is detected. When the refractive index of the sample solution increases, for example, when the slit image moves to the element portion 2-2 side, the signal processing circuit calculates and outputs S = C · (s2−s1) / (s2 + s1). Here, s1 and s2 are detection outputs of the light receiving element portions 2-1 and 2-2, respectively, and C is a constant. The output changes according to the amount of change in the refractive index of the sample. On the light receiving element, when all of the slit image 6 enters the light receiving element portion on one side as shown in FIG. 3B, the signal is saturated. Therefore, at the start of measurement, the slit image 6 is adjusted so as to be centered across the separation straight line 4 as shown in FIG.

An example of the use of an analyzer that employs the principle of differential refraction as a detector is a liquid chromatograph, but the liquid chromatograph has two uses: analysis and fractionation. In the case of fractionation, a sample with a relatively high concentration is flowed. Therefore, if a high-sensitive differential refractive index detector for analysis is used, the signal is saturated. Therefore, even if the flow cell is not replaced with a differential refractive index detector, the light receiving element and the subsequent signal processing circuit can receive light so that it can be used for both high sensitivity and low sensitivity applications such as analysis and fractionation. A differential refractive index detector in which an element is divided into four has been proposed. (Patent Document 1)
Patent No. 2504356

  If the position at which the slit image is adjusted (balanced) by the zero glass so as to cross the center line of the light receiving element is set to zero, the slit image moves to either the plus side or the minus side when the sample is measured. For a series of analysis (sorting), only the positive side or the negative side is often used for measurement. In an actual differential refractive index detector, one of the measurement conditions is a setting item called “polarity”. The operator sets this setting item according to the object to be measured, and a series of analyzes (minutes) is performed under that condition. Take). If the polarity is set to (+), the received light signal is processed with the amount of change from the zero point to the plus side as positive, with the setting to measure the sample whose slit image is displaced in the plus measurement area, If set to-), the received light signal is processed with the amount of change from the zero point to the minus side as positive.

  When measuring with the polarity set to (+), the percentage of light used in the negative measurement area of the light receiving element decreases drastically, and the light reception area of the slit image is divided into a positive measurement area and a negative measurement area. The equalization always means that one of the measurement areas is not used, and the limited light receiving area is not effectively used.

  As a result of intensive studies, the present inventors have found a configuration for effectively using the light receiving region of the light receiving element. That is, the present invention transmits the measurement light that has passed through the slit to the flow cell through which one of the two cells partitioned by the wall inclined with respect to the optical axis of the measurement light passes through the sample solution and the other through the reference solution. The differential refractive index detection detects the displacement of the slit image by reflecting the transmitted light by a mirror and imaging the measurement light that has passed through the flow cell again as a slit image across the divided light receiving elements. A polarity setting unit for setting the polarity related to the measurement sample, and a zero glass for translating the slit image on the light receiving element, and operating the zero glass based on the setting content of the polarity setting unit, The slit image is shifted in advance.

  By operating the zero glass based on the setting of the polarity setting unit, the slit image that has been spread over the divided light receiving portions in the related art is unevenly distributed in any of the light receiving elements.

  In the setting of polarity (+), the balance of the slit image is unevenly distributed in advance to the minus side, so that a wide range for measuring the signal appearing on the plus side can be secured, and vice versa. .

  The state of balance position adjustment according to the present invention will be described with reference to FIG. In the state where the same solution (showing the same refractive index) is circulating in the sample solution side cell and the reference solution side cell, conventionally, as shown in (a), the slit image is balanced so as to evenly cover the divided light receiving regions. The In the differential refractive index detector adopting the present invention, it is possible to determine which measurement area to use with the setting contents (+/−) related to the polarity set by the operator. The balance is shifted in the direction opposite to the direction of displacement. A control unit (not shown) that has determined the set content of the polarity drives the motor driving unit 34 to activate the zero glass 28. According to the present invention, when the polarity is set to (+), the balance is as shown in (b), and when the polarity is set (-), it is balanced as shown in (c). In other words, when the target substance flows into the sample solution side cell and there is a difference in the refractive index between the liquid on the sample solution side and the liquid on the reference solution side, the slit image is balanced so that the range in which the slit image can be displaced is widened. It is.

  When measurement starts and the target substance flows into the cell on the sample solution side, a difference occurs in the refractive index between the liquid on the sample solution side and the liquid on the reference solution side, and the slit image formed on the light receiving element is displaced, Based on the amount, the light receiving element emits a signal and acts as a differential refractive index detector.

  As described above, if all of the slit image enters the light receiving element on one side, the signal will be saturated, so the output ratio of signals from the positive and negative measurement areas, for example, according to the polarity setting The zero glass may be operated so that is 1: 2 (2: 1).

  The above-described embodiment is merely an example of the present invention, and it is obvious that the present invention includes modifications and changes appropriately within the scope of the present invention.

  The present invention is used as a detector of a liquid chromatograph apparatus used for analysis and fractionation.

It is a figure which shows the mode of image formation of the slit image on the light receiving element of the differential refractive index detector of this invention. It is a figure which shows the structure of a general differential refractive index detector. It is a figure which shows the principle of a general differential refractive index detector.

Explanation of symbols

2-1 ... Element part 2-2 ... Element part 6 ... Slit image 8 ... Light source 10 ... Slit 12 ... Measuring light 14 ... ··· Lens 16 ··· Flow cell 18 ··· Wall 20a, b · · · Cell 22i ··· Liquid inlet 22o · · · Outlet 24i · · · Liquid inlet 24o · · · ··· Outlet 26 ··· Mirror 28 ··· Zero glass 30 ··· Light receiving element 32 ··· Pulse motor 34 ··· Motor drive circuit 36 ··· Signal Processing circuit

Claims (1)

One of the two cells partitioned by a wall inclined with respect to the optical axis of the measurement light is transmitted through the slit to the flow cell through which the sample solution passes and the other passes through the reference solution, and the transmitted light is mirrored. In the differential refractive index detector for detecting the displacement of the slit image by forming the measurement light reflected by and transmitted through the flow cell again as a slit image across the divided light receiving elements,
A polarity setting unit for setting the polarity related to the measurement sample;
Comprising zero glass for translating the slit image on the light receiving element;
A differential refractive index detector, wherein the slit glass is preliminarily shifted by operating the zero glass based on the setting content of the polarity setting unit.

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