JPS60250230A - Differential refractometer - Google Patents

Abstract

PURPOSE:To enable common use for high-sensitivity fine analysis and low-sensitivity sharing, by switching of two different slit-widths from one to other, and changing light quantity of a source of an incident light to an optical cell in such a way that the quantity is proportional to the slit-width. CONSTITUTION:When a high-sensitivity slit 8-1 is set by switching and specimen liquid of a refraction coefficient difference DELTAn and reference liquid are allowed to pass through an optical cell 12, an image on an optical sensor 2 makes a displacement by DELTAd and from a detecting signal of the sensor 2, an output propertional to DELTAd/d1 [(d): width of image] is obtained to an output of a subtraction element 28 through I-V convertors 20, 22, addition element 24 subtraction element 26. Further, a circular disc 8 for slit is rotated by changeover switch 30, motor driving circuit 32, and motor 10, and by changing to a low-sensitivity slit 8-2, a width of an image is multiplied by 10 times and by a source circuit 34, light quantity of the light source 4 is cut down to 1/10 in order not to canse a change of output of the element 24. By these procedures, the sensitivity is cut down to 1/10 and a linearity range is boosted by 10 times in proportion to the slit-widths.

Description

Detailed Description of the Invention (a) Purpose (Field of Industrial Application) The present invention relates to a device for optically detecting the difference in refractive index that occurs between transparent liquids, such as in a liquid chromatograph detector. be.

(Prior Art) A differential refractometer detector is used as a detector in a high-performance liquid chromatograph, and its applications include a high-sensitivity differential refractometer for trace analysis and a low-sensitivity differential refractometer for preparative separation. These are usually commercialized as separate products.

In addition, since the sensitivity changes depending on the angle of incidence of light on the partition wall that separates the two containers of the optical cell,
In some cases, sensitivity depending on the application may be obtained by replacing the optical cell with an optical cell having a different partition wall angle.

(Problem to be solved by the invention) In order to change the sensitivity depending on the application, the optical cell is replaced,
Making adjustments is a troublesome task.

The present invention allows the sensitivity and linearity range to be increased or decreased at the same time with a single device and with a simple switching operation.
The purpose of this invention is to provide a differential refractometer that can be used for two purposes: high-sensitivity microanalysis and low-sensitivity preparative separation.

(B) Configuration (Means for solving the problem) The present invention involves injecting light into an optical cell having two containers separated by a partition wall that is inclined with respect to the direction of incidence of the light. A differential refractometer that measures the displacement of transmitted light corresponding to the difference in refractive index is equipped with two types of slits with different slit widths and means for controlling the amount of light from the light source that enters the optical cell. This is a differential refractometer that changes the light intensity of the light source in inverse proportion to the slit width at the same time as switching.

(Operation) It is assumed that the optical sensor 2 shown in FIG. 2 is divided into two parts in the displacement direction of the measurement light. One side is S side 2-1 and the other side is R side 2-2. When there is no difference in refractive index between the liquids in the two containers of the optical cell, two optical sensors 2-1 and 2-2 are used.
Light from a slit image with an area of dXa is incident on the center of the . d
corresponds to the slit width, and a corresponds to the slit length.

Next, if the refractive index between the liquids in the two containers changes by 80, the image of Surin I- on the optical sensor 2- will be displaced by Δd in accordance with the refractive index difference Δn, and this amount of displacement will be It is proportional to Q・Δn/n. a is the distance between the optical cell and the optical sensor 2, and n is the refractive index of the solvent.

If the light intensity of optical sensor 2'' is 2, then S side optical sensor 2
-1. The signal is appearing on each of the R side optical sensors 2-2
, ir are ((d/2)+Δd) T a −・= (1)((
d/2)-Δd) Ta--(2).

In the present invention, the slit width is multiplied by M, and the light intensity of the light source is set to 1. /M, then d-)Md, I→I/M, so in equations (1) and (2), the steady term that does not include Δd remains unchanged, but the displacement Δd corresponding to the refractive index difference Δn The signal due to this, that is, the sensitivity becomes Δd·Ia/M, which decreases to 1/M.

Also, the linearity range is -3= where d is M times Therefore, it becomes M times larger.

Furthermore, there is no need to change the signal processing system even by switching the slits.

(Example) FIG. 1 represents one embodiment of the invention.

4 is a light source, 6 is a lens, and 8 is a slit disk.The disk 8 includes a slit 8-1 for high-sensitivity analysis with the same length and a slit width d, and a slit 8-1 with a slit width 10 times that width. A 10d separation slit 8-2 is provided, and a motor 10
Both the slits 8-1 and 8-2 can be switched by the rotation of the slits 8-1 and 8-2. Reference numeral 12 denotes an optical cell having two containers through which a sample solution and a control solution are passed or accommodated, respectively.The two containers are separated by a partition wall 14, and the two containers are separated by a partition wall 14. Light enters this optical cell through a lens 16, and as it passes through the partition wall 16, it is displaced by the refractive index difference Δn between the liquids in both containers. Reference numeral 18 denotes a reflecting mirror for making the transmitted light of the optical cell 12 enter the optical cell 12 again to amplify the displacement.

4- The light reflected by the reflection mirror 18 passes through the optical cell 12 and the lens 16 again and forms an image of the slit 8-1 or 8-2 on the optical sensor 2 as shown in FIG. The optical system is designed so that the light intensity of the slit image on the optical sensor 2 is uniform for both slits 8-1 and 8-2.

Returning to FIG. 1, 20.22 is the S side 2-1.2 of the optical sensor, respectively. This is an i-V converter that receives the detection signal of the R side 2-2 as a current value and converts it into a voltage value, and the respective output signals Vs and Vr are proportional to the above-mentioned equations (1) and (2).

, 24 is a summation element that calculates the sum (vs + Vr) of the rain detection signals, and 26 is a subtraction element that calculates the difference (Vs - Vr). Reference numeral 28 is a division element for correcting light intensity fluctuations, and inputs signals from the summation element 24 and the subtraction element 26 to calculate (Vs - Vr) / (Vs
+V r ) and sends a signal to the recorder.

30 is the slit 8-1. s-2 and a changeover switch for changing the light intensity of the light source 4; 32 is a motor drive circuit that rotates the motor 10 to change the slit according to the output signal of the changeover switch 30; 34 is a motor drive circuit for switching the slit; This is a light source power supply circuit that controls the light amount of the light source 4 so that the output signal (Vs+V r ) of the summation element 24 becomes constant.

Now, assume that a narrow high-sensitivity slit 8-1 is set as shown in FIG. 1 in order to perform a trace analysis. First, when there is no difference in the refractive index of the solutions in both containers of the optical cell I2, the zero position is optically adjusted so that the slit image of the optical sensor 2'' is correctly centered.

Next, if the sample liquid and the control liquid are passed through both containers of the optical cell 12 and the difference in refractive index is 80, then the optical sensor 2
"The second displacement Δd is Δd=2Q・Δn/n...(3)
becomes. At this time, the width of the image of the slit I-8-1 is assumed to be dl.

The detection signals from the S side 2-] and the R side 2-2 of the optical sensor 2 are input to the r-v converter 20.22, and the summation element 24
, the signal output by the division element 28 via the subtraction element 26 is proportional to Δd/d 1 (4).

Next, assume that the motor 10 is operated via the motor drive circuit 32 by the changeover switch 30 to rotate the slit disk 8 by 180 degrees, and the slit is switched to the wide low-sensitivity slit 8-2 for preparative separation. . At this time, the width d of the slit image on the optical sensor 2 increases ten times as much as before the slit switching. The light source power supply circuit 34 changes the light amount of the light source 4 so that the output signal of the summation element 20 does not change before and after switching the slit, and reduces it to 1/10. And the division element 28
The output signal becomes 1/10 of Δd/d+, that is, the sensitivity becomes 1/10, and the linearity range becomes 10 times wider in proportion to the slit width.

In the embodiments described above, in order to control the light amount of the light source as the slits are switched, the output signal (V
Since feedback is applied to the light source power supply circuit 34 so that s + V r ) remains constant, accurate light amount control is achieved. The amount of light may be changed to the amount of light that has been set.

In addition, as a switching mechanism for slits 8-1 and 8-2,
In addition to rotating the slit disk 8 as in the above embodiment, various mechanisms can be used, such as switching by a sliding method.

It would be convenient if the switching between the slit and the amount of light from the light source could be done automatically by operating only one button on the changeover switch.

(c) Effects of the invention According to the differential refractometer of the present invention, one device can be used for both a high-sensitivity differential refractometer for trace analysis and a low-sensitivity differential refractometer for preparative separation. Moreover, the switching operation is extremely simple.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a detection method using an optical sensor. 2... Light sensor, 4... Light source, 8-1
．． 8-2... Slit, 12... Optical cell, 30... Changeover switch, 32...
- Motor drive circuit, 34... Power supply circuit for light source. Agent Patent Attorney Shigeo Noguchi

Claims (1)

[Claims] (1) Two parts separated by a partition wall that is inclined with respect to the direction of light incidence.
In a differential refractometer, light is incident on an optical cell having two containers and the displacement of the transmitted light corresponding to the difference in refractive index of the liquid in both containers is measured. A differential refractometer comprising means for controlling the amount of incident light from a light source, and changing the amount of light from the light source in inverse proportion to the width of the slit at the same time as the slit is switched.