JPS6231294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser light scattering photometer for detecting the intensity of light scattered from a liquid to be detected and determining the molecular weight, etc. of a solute component in the liquid. The present invention provides a device for accurately measuring scattered light intensity using a novel optical system and electrical system.

Although the light scattering method is important as a measurement method for determining the molecular weight, molecular size, etc. of solute molecules in a solution, it is not necessarily widely used because the measurement operation is complicated. For example, when determining molecular weight using a conventional light scattering method using a mercury lamp as a light source, the scattered light intensity is usually measured at angles ranging from 30° to 150° for several sample solutions with different concentrations. It is necessary to extrapolate the concentration and angle to zero using methods such as , Zimm plot, etc.

However, the laser light scattering method makes it possible to determine the molecular weight without performing both of the above extrapolation operations. That is, according to a light scattering photometer using a laser as a light source, the intensity of scattered light can be measured at a small angle of 5 degrees or less, so extrapolation to a zero angle is actually unnecessary. Furthermore, since the intensity of the incident light is high, a very dilute solution can be used as a measurement sample, so extrapolation to zero concentration is usually not necessary. In this case, since the scattering intensity to be measured is proportional to the product of the molecular weight of the solute and the solution concentration, by using a laser light scattering photometer as a molecular weight detector in conjunction with the concentration detector, it is possible to measure the molecular weight of the solute in the liquid to be detected. can be measured continuously.

Conventionally known laser light scattering photometers have a special structure, especially the measurement cell part, which requires special processing precision and is impractical.
Fluctuations in the intensity of the incident light directly appear as fluctuations in the intensity of the scattered light, making it difficult to obtain stable measured values.Therefore, there is a need for a more practical photometer. As a result of repeated research to improve these drawbacks, the inventors of the present invention have developed an optical system, a corresponding electrical system, and a structure simpler than the conventional one to eliminate fluctuations in the intensity of scattered light caused by fluctuations in the intensity of incident light. This is a completed laser light scattering photometer characterized by having a measurement cell.

That is, the present invention provides a laser light scattering photometer for measuring the intensity of scattered light of a liquid to be detected, in which a measurement cell and an annular slit mounted around an optical trap are arranged such that their central axes are aligned with the light of the incident laser beam. a transmitted light intensity detecting section arranged to coincide with the axis and detecting a transmitted light component reflected by the optical trap; and a scattered light intensity detecting section detecting a scattered light component limited by the annular slit. further forming a fluctuation elimination circuit that detects a fluctuation in the transmitted light intensity detected by the transmitted light intensity detector and inputs an output signal corresponding to the fluctuation to the scattered light intensity detector, With this output signal,
A laser light scattering photometer is configured to cancel fluctuations in the output of the scattered light intensity detection unit caused by fluctuations in the intensity of the incident light, and in the laser light scattering photometer, the measurement cell has a center axis that corresponds to the light beam of the incident laser beam. A cell component having a cylindrical light flux passage part with a hole formed so as to coincide with the axis and a detected liquid flow path part with a cylindrical hole formed so as to be connected to the cylindrical light beam passage part; This is a laser light scattering photometer which is a flow type cell consisting of two glass blocks attached to the front and rear surfaces of the cell component.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of an example of an optical system in a photometer of the present invention.

The main part of the photometer of the present invention is a laser light scattering photometer that measures the intensity of scattered light of a liquid to be detected. Scattered light limited by the transmitted light intensity detector 10 and the annular slit 4, both of which are arranged so as to coincide with the optical axis of the laser incident beam, and which detects the transmitted light component reflected by the optical trap 3. A pair of detection units including a scattered light intensity detection unit 9 for detecting components is provided. By measuring the intensities of the transmitted light component and the scattered light component, fluctuations in the scattered light intensity resulting from fluctuations in the incident light intensity are eliminated.

Examples will be described below.

The laser incident light that has passed through the slit 1 is separated into two components, a scattered light component scattered from the liquid to be detected and a transmitted light component, in a measurement cell 2 having a central axis that coincides with the incident optical axis. The transmitted light is collected at a right angle to the optical axis of the incident light beam by an optical trap installed at the center of the annular slit 4 whose central axis coincides with the optical axis of the incident light beam, and whose light-receiving surface has a plane at 45 degrees to the optical axis of the incident light beam. The reflected light passes through a neutral filter 8 to a photomultiplier tube for detecting transmitted light (hereinafter referred to as R-
(abbreviated as PM) is received at 10. On the other hand, the scattered light passes through the annular slit 4, which has a central axis that coincides with the incident optical axis and corresponds to the specific scattering angle θ, and is focused by the lens 5. After passing through the light receiving slit 6, the scattered light 7 becomes a parallel light beam, and a photomultiplier tube for detecting scattered light (hereinafter abbreviated as S-PM) 9
The light is received by the The size of the annular slit can be selected so that the scattering angle θ is usually 10° or less, preferably 5° or less.

In this way, the transmitted light component and the scattered light component detected by the two detection units R-PM10 and S-PM9, respectively, are derived from fluctuations in the intensity of the incident light in the electric circuit configured as shown in Figure 2. This acts to eliminate fluctuations in the intensity of scattered light.

In other words, this eliminates fluctuations in the measured value of scattered light intensity and promises improved measurement stability and measurement accuracy.

FIG. 2 schematically shows an example of the above-mentioned electric circuit configured to eliminate the influence of fluctuations in the intensity of incident light. The photomultiplier tube applying power supply section 17 is connected to the R-PM 10 so that the tube reference voltage setting section 16 is connected in parallel to the amplifier IC.3, and the output of the amplifier IC.3 is fed back. to form a fluctuation cancellation circuit 18, and the output signal of the applied voltage-HV obtained from this fluctuation cancellation circuit 18 is simultaneously input to the S-PM9 and outputted via the amplifier IC.1. This is the constructed electrical control circuit.

That is, the intensity of the incident light is converted into an electrical signal by the R-PM, amplified by the circuit IC.2, and output as an input to the circuit IC.3.

In IC.3, the input from IC.2 is compared with the reference voltage PM.Volt from the photomultiplier tube reference voltage setting section 16, and the photomultiplier tube application power supply section 17 is set so that the difference between the two is always zero. Applied voltage - HV is activated. For example, assuming that there is an increase in the incident light intensity, the output current of the S-PM increases and the output from IC.1 also increases, resulting in an increase in the sensitivity of the photometer. On the other hand, the output current from R-PM also increases, and the voltage output converted by IC.2 also increases. In that case, the reference voltage of IC.3 is
Since the voltage increases more than the PM.Volt setting signal, the control signal to the photomultiplier tube applied voltage power supply section 17 is lowered until the difference between this signal and the output from IC.2 becomes zero, and the negative high voltage applied voltage is increased. decrease. lowered
Since the change in PM.Volt is also supplied to S-PM at the same time, the sensitivity of the photometer (S-PM) is compensated to always remain constant.

Conversely, when the incident light intensity decreases, the operation is completely opposite to the above to compensate for the fluctuation. in this way,
The intensity of the incident light is continuously monitored by the R-PM, and the applied voltage to the S-PM is continuously controlled so that fluctuations in the intensity of the incident light do not affect the output of the photometer. Output stability is significantly improved.

FIGS. 3a and 3b show schematic structural diagrams of a measuring cell as an embodiment of the present invention.

All figures show cross sections parallel to the laser incident light.

The measurement cell of the present invention includes a cylindrical light beam passing section 12 with a hole bored so that its central axis coincides with the optical axis of the incident laser beam, and a cylindrical hole bored so as to connect to the light beam passing section 12. A cell component having a liquid flow path to be detected, that is, an inlet liquid flow path 13 and an outlet liquid flow path 14; This is a flow type cell composed of glass blocks 11a and 11b.

The liquid to be detected is introduced from the inlet liquid flow path section 13, passes through the light flux path section 12, and is sent to flow out from the exit liquid flow path section 14.

At this time, the incident light passes through the front glass block 11.
a, the light passes through the central axis of the light flux passage section 12 and the rear glass block 11b, and is separated into a transmitted light component and a scattered light component.

The cell constituent material 15 in the shaded area is preferably one that reflects as little light as possible; for example, a synthetic resin with good solvent resistance such as black polytetrafluoroethylene or polychlorotrifluoroethylene may be processed and applied thereto. can.

The light flux passage portion 12, the inlet liquid flow path portion 13, and the outlet liquid flow path portion 14 can be easily manufactured by drilling holes in the cell constituent material into a cylindrical shape.

In the measurement cell shown in FIG. 3a, the liquid to be detected is sent from the inlet liquid flow path section 13 to the light flux path section 12, and after passing through the cell connection surfaces of the front and rear glass blocks 11a and 11b. , is discharged from the outlet liquid flow path section 14.

In the measurement cell shown in FIG.
The liquid passes through the cell connection surface of 1a or 11b, is sent to the luminous flux passage section 12, and is sent to the other glass block 1.
The liquid flows out from the outlet liquid flow path section 14 through the cell connection surface of 1b or 11a.

The size of the light flux passage in the flow-type measurement cell shown in the above example is not particularly limited, but for example, the diameter of the cylinder is 4 mm or less, preferably 2 mm or less, and the length of the cylinder is 20 mm or less, preferably teeth
It is desirable that it be 10mm or less.

Since the flow cell of the present invention is a small-capacity cell with a capacity of 100 μl or less, usually 50 μl, it has the advantage of being able to perform highly accurate measurements with a small amount of measurement sample. Furthermore, since the cell constituent material is black and can absorb light reflected from the liquid-glass interface, it is possible to measure the scattering intensity with a low level of stray light. Furthermore, the light flux passage section has a simple cylindrical shape and has a small dead volume, so that each eluted component flows out from the molecular weight separation device (GPC, FFF, etc. described later) without disturbing the flow of the detected liquid. It is particularly excellent as a detection device.

The present invention particularly provides a flow-type laser light scattering photometer for continuously measuring the scattering intensity of a liquid to be detected with high precision. The effects of the invention can be fully demonstrated by applying the laser light scattering photometer of the present invention as a detector for separation equipment such as GPC (GPC) and field flow fractionation (FFF). It makes it possible to directly evaluate the molecular weight of each eluted component of the detection liquid, and adds, for example, a molecular weight analysis function to the separation function of GPC.

Tetrahydrofuran (THF) as eluent
As a result of applying the laser light scattering photometer of the present invention to a GPC device, we investigated the stability of the response corresponding to the fluctuation of the baseline, that is, the scattering intensity of the solvent THF. It was confirmed that it was less than 0.1% and that extremely stable measured values could be obtained. For comparison, the same measurement was performed in the case where the circuit for eliminating variations in incident light intensity shown in FIG. 2 was not activated, and as a result, the baseline variation was 4%. From this, it was confirmed that the system for eliminating fluctuations in incident light intensity according to the present invention was effectively utilized.

Note that it was possible to determine the molecular weight of each eluted component from the response ratio of two chromatograms obtained from GPC and the laser light scattering photometer of the present invention.

[Brief explanation of the drawing]

The drawings show an embodiment of the laser light scattering photometer of the present invention, in which Fig. 1 is a schematic diagram of the configuration of its optical system, Fig. 2 is a schematic diagram of the electric circuit, and Fig. 3 a and b are measurement cells. FIG. Symbol explanation, S-PM: Photomultiplier tube for detecting scattered light, R-PM: Photomultiplier tube for detecting transmitted light, IC.
1, 2, 3: amplifier, 1, 6: slit, 2: measurement cell, 3: optical trap, 4: annular slit,
5, 7: Lens, 8: Neutral filter, 9, 10:
Photomultiplier tube, 11a, b: Glass block, 1
2: Luminous flux passage part, 13: Inlet liquid flow passage part, 14:
Outlet liquid flow path section, 15: Cell constituent material, 16: Photomultiplier tube reference voltage setting section, 17: Photomultiplier tube applied voltage power supply section, 18: Fluctuation cancellation circuit.

Claims (1)

[Scope of Claims] 1. In a laser light scattering photometer that measures the intensity of scattered light of a liquid to be detected, a measurement cell and an annular slit mounted around an optical trap are arranged so that their central axes are aligned with the light beam incident on the laser beam. a transmitted light intensity detecting section arranged to coincide with the axis and detecting a transmitted light component reflected by the optical trap; and a scattered light intensity detecting section detecting a scattered light component limited by the annular slit. further forming a fluctuation canceling circuit that detects a fluctuation in the transmitted light intensity detected by the transmitted light intensity detector and inputs an output signal corresponding to the fluctuation to the scattered light intensity detector. . A laser light scattering photometer, characterized in that the output signal is configured to offset fluctuations in the output of the scattered light intensity detection section caused by fluctuations in the intensity of the incident light. 2 The measurement cell has a cylindrical light beam passing section with a hole bored so that its central axis coincides with the optical axis of the incident laser beam, and a cylindrical liquid flow path section with a cylindrical hole connected thereto. Claim 1, which is a flow type cell, is composed of a cell component having a laser beam and two glass blocks attached to the front and rear surfaces of the cell component with respect to the laser incident light beam.
Laser light scattering photometer described in Section 2.