JPS63274843A - Temperature control method for differential refractometer - Google Patents

Abstract

PURPOSE:To measure a difference in refraction factor with high sensitivity by detecting directly or indirectly the temperature of sample liquid which flows in a heating device and making its set temperature nearly equal to the temperature of the sample liquid. CONSTITUTION:A moving phase solvent fed by a reciprocating pump 10 passes through a damper 11 to reduce pulsation, passes through a column 14 put in a column oven 12, and passes through a sample pipe S and a differential refractometer 16 together with a separated component of a sample injected by an injector 15 to flow out of a sample pipe S'. Here, the reverse surface of the floor part 18A of an optical block 18 and a heater are fitted to the refractometer 16 and the whole of the block 18 is held at nearly uniform temperature. Light flux emitted by a light source chamber 22, on the other hand, is collimated by a lens 28, reflected by a planar mirror 32, and transmitted through an objective cell and a sample cell in a cell chamber 30, and a compensating plate 26 to reach a photodetecting chamber 24. Then the difference in refractive index between the sample liquid and objective liquid is measured by detecting the deviation angle between the incident luminous flux to the lens 28 and projection luminous flux from the lens 28.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a temperature control method for differential refraction applied to a liquid chromatograph using a reciprocating pump.

[Prior art] The temperature coefficient of the refractive index of a liquid is large, 1O- per 1°C.
A refractive index change of about 5 occurs.

Therefore, in a differential refractometer, a sample liquid line and a reference liquid line are placed inside the heating device, and the temperature of the liquid flowing through both lines is adjusted using a temperature controller so that they are at the same set temperature. (Special Publication No. 50-10671).

According to such a differential refractometer, the difference between the refractive index of the sample liquid and the refractive index of the reference liquid can be detected with a sensitivity of about 10 −9 .

The purpose of temperature control is to equalize the temperature of the sample solution and control solution by heating, so this set temperature may be fixed, or set at, for example, 20°C, 130°C, 140°C, 5
It can be set to either 0'C. In the latter case, the temperature is usually set to about 10"C higher than the ambient temperature.

[Problems to be solved by the invention] However, when a differential refractometer is used in a liquid chromatograph that transports liquid with a reciprocating pump, the flow rate increases and decreases in a pulsed manner due to pulsation, and the time it takes for the liquid to pass through the heating device increases. Because it fluctuates,
The noise component included in the output signal of the differential refractometer becomes larger when the temperature is adjusted.

For this reason, it is necessary to slow down the output fluctuations of the differential refractometer, making it impossible to perform measurements with high sensitivity.

This tendency is particularly remarkable for solvents with relatively large temperature coefficients of refractive index, such as tetrahydrofuran and chloroform.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a temperature control method for a differential refractometer that can measure a refractive index difference with high sensitivity.

"Background of the Invention" The present invention was devised based on the discovery of the following facts by the present invention.

Air temperature Tc in the column oven of liquid chromatograph
and the temperature TR of the liquid sending tube in the heating device of the differential refractometer.
We measured the amplitude N (unit: refractive index) of the noise component included in the output of the differential refractometer based on the pulsation that occurs when pumping liquid with a reciprocating pump under various combinations of
The following results were obtained.

For example, when Tc=20°C, TR=20″C, N≦
l0-1', but if Tc is kept at 20°C and TR is 4
0°C+,: t le(!: N = 2, 7 x
I O-' (!: Author L < becomes bigger, TR is 50
When the temperature was increased to °C, it became even larger, N = 4, 2 x 10'□a. However, at TR-40°C, Tc=4
When the temperature was set to 0°C, N=2.2xlO-8, and the noise component was reduced by 0.5xlO-''.

That is, the inventors have discovered that by setting Tc=TR, the noise component based on pulsation can be reduced.

Note that the temperature of the sample liquid supplied into the heating device of the differential refractometer is difficult to measure directly because the inner diameter of the liquid pipe is approximately 0.1-1.0 mm, so the temperature of the sample liquid supplied into the heating device of the differential refractometer is not easily measured. By measuring Tc, the temperature of the sample liquid was indirectly measured.

Further, the amplitude data of the noise component is a value obtained by subtracting the amplitude of the noise component when the liquid feeding is stopped from the amplitude of the noise component during liquid feeding, and is caused only by pulsation.

[Means for solving the problem] In the present invention, the temperature of the liquid flowing into the refractive index measurement cell from the sample liquid pipe and the control liquid pipe arranged inside the heating device becomes the set temperature. In a method for controlling a temperature for a differential refractometer in which the energy supplied to the heating device is adjusted by a temperature controller, the temperature of the sample liquid flowing into the heating device is directly or indirectly detected, and the set temperature is adjusted to It is characterized in that it is made to approximately match the temperature of the sample liquid.

[Example] The present invention will be explained in detail based on FIG.

FIG. 1 shows a schematic configuration of a liquid chromatograph.

The mobile phase solvent sent by the reciprocating pump 10 passes through the damper 11 to reduce pulsation, passes through the column 14 housed in the column oven 12, and enters the sample liquid tube S together with the separated components of the sample injected by the injector 15. The sample liquid passes through the differential refractometer 16 and flows out from the sample liquid tube S°.

The differential refractometer 16 is of a polarization type and is constructed in a well-known manner. That is, in the differential refractometer 16, a heater 20 is attached to the lower surface of the floor I118A of the optical block 18 in the form of a box made of cast metal, and the entire optical block 18 is kept at a substantially uniform temperature. A light source chamber 22, a photodetector chamber 24, a compensation plate 26, a lens 28, a cell chamber 30.
A plane mirror 32 is disposed, and a beam of light emitted from the light source chamber 22 is parallelized by a lens 28 and sent to the cell chamber 30.
The light passes sequentially through a triangular prism-shaped sample cell and a control cell (not shown) in the cell chamber 30, is reflected by a plane mirror 32, and again sequentially passes through a control cell and a sample cell in the cell chamber 30, and passes through a compensator 26. The photodetector chamber 24 is reached. This compensating plate 26
It is rotated by operating the compensating plate adjusting section 34 attached to the lower surface of A, thereby performing zero adjustment.

The refractive index difference between the sample liquid and the control liquid is measured by detecting the polarization angle between the light beam entering the lens 28 and the light beam exiting the lens 28 .

The inside of the floor part 18A has a well-known configuration, and a spirally bent sample liquid tube S and a control liquid tube R are passed through the inside of the floor part 18A. The sample liquid tube S and the control liquid tube R in the floor section 18A are connected to the sample liquid tube S' and the control liquid tube R' through the sample cell and the control cell in the cell chamber 30, respectively. Before sample injection, the sample liquid tube S' and the reference liquid tube R are communicated with each other, and the same mobile phase solvent passes through both liquid tubes. During the refractive index difference measurement, the reference liquid pipe R on the inlet side of the optical block 18 and the reference liquid pipe R° on the outlet side of the cell chamber 30 are closed by valves not shown.

The liquid temperature in the sample cell and the control cell is determined by the optical block 18.
This is indirectly detected by detecting the temperature of the upper surface of the floor ff1l 8A, for example, by means of a temperature sensor 36. This detected temperature signal is fed back to the temperature regulator 38.

On the other hand, the temperature of the sample liquid flowing into the optical block 18 is
It is indirectly detected by detecting the temperature of the atmosphere in a suitable part of the column oven 12, for example, the column oven 12, by means of a temperature sensor 40. This detection signal is supplied to the temperature indicator 42, where it is converted into a temperature value, the temperature is displayed, and a temperature signal STC is output.

When the interlocking automatic/manual selector switch 44.44 is set to auto (A), this temperature signal S T c
is supplied as a temperature setting signal to the temperature regulator 38 via the automatic/manual changeover switch 44, 44'. When the automatic/manual changeover switch 44.44° is set to manual (M), the operator can set the temperature indication value T of the temperature indicator 42.
C visually and operate the temperature setting device 46 to set the set temperature Tc.
Make it. In this case, the setting signal output from the temperature setting device 46 is supplied to the temperature controller 38 via the automatic/manual changeover switch 44'. The temperature regulator 38 adjusts the power supplied to the heater 20 via the driver 48 so that the temperature detected by the temperature detector 36 becomes the set temperature.

Therefore, the temperature of the sample liquid and the control liquid in the cell chamber 30 become the same, and this temperature becomes approximately the same as the temperature of the sample liquid flowing into the optical block 18.

Therefore, for the above-mentioned reason, the amplitude of the noise component based on the pulsation of the sample liquid included in the signal SP output from the photodetector chamber 24 is reduced. Therefore, the value set by the sensitivity setting device 50 can be increased, and the refractive index difference can be measured with high sensitivity. For example, T e described in the Background of the Invention column above.
In the example of = T R = 40°C, the sensitivity improves by about 20%.

The signal SP is supplied to the signal processing circuit 52, and the signal processing circuit 52 amplifies this signal with an amplification factor according to the setting value from the sensitivity setting device 50, converts it into a value proportional to the refractive index difference,
It is supplied to the recorder 54.

In addition, although the above embodiment describes the case where the present invention is applied to a polarization type differential refractometer, the present invention is not limited to this.
Of course, the present invention can also be applied to differential refractometers such as Fresnel type or interference type.

[Effects of the Invention] In the temperature adjustment method for a differential refractometer according to the present invention, the temperature of the sample liquid flowing into the heating device is detected directly or indirectly, and the sample liquid pipe line and A temperature controller adjusts the energy supplied to the heating device so that the temperature of the liquid flowing from the control liquid pipe to the refractive index difference measurement cell approximately matches this detected temperature. Since it is possible to reduce the noise component contained in the detection signal based on the pulsation that occurs during liquid feeding, there is an excellent effect that the refractive index difference can be measured with high sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of an apparatus to which the present invention is applied. 16: Differential refractometer 18: Optical block 20: Heater 30: Optical cell chamber 36.40: Temperature detector 44.44'': Automatic/manual changeover switch S, S': Sample liquid tube R, R': Control liquid tube

Claims (1)

[Claims] Supply the liquid to the heating device so that the temperature of the liquid flowing into the refractive index measurement cell from the sample liquid pipe and the control liquid pipe arranged inside the heating device reaches a set temperature. In a temperature control method for a differential refractometer in which energy is controlled by a temperature controller, the temperature of the sample liquid flowing into the heating device is directly or indirectly detected, and the set temperature is made to substantially match the temperature of the sample liquid. A temperature control method for a differential refractometer, characterized in that: