JP3675057B2 - Absorbance detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an absorbance detector for analyzing an absorbance by putting a substance to be analyzed in a cell, specifically, an absorbance as used in an absorptiometer, a liquid chromatograph, an electrophoresis device, a flow injection device and the like. Relates to the detector.
[0002]
[Prior art]
In an analyzer such as a liquid chromatograph, an absorbance detector may be used to measure the absorbance of a sample in a cell. As one type of such an absorbance detector, there is a type in which cell transmitted light is dispersed with a dispersion element such as a diffraction grating and guided to a detector such as a photodiode array to obtain an absorbance spectrum.
[0003]
FIG. 1 is a diagram showing a configuration of an absorbance detector portion of a liquid chromatograph using a linear image sensor such as a photodiode array as a detector. Reference numeral 2 denotes a liquid chromatograph flow cell, in which a cylindrical flow path is formed. A liquid introduction channel and a discharge channel are formed at both ends of the cylindrical channel, and an effluent from the column to be analyzed flows. One end surface of the cylindrical flow path is a light incident surface of the spectroscopic optical system, and the other end surface is a light transmission surface. Reference numeral 4 denotes a light source, and reference numeral 6 denotes a lens. Light from the light source 4 is collected by the lens 6, passes through the cylindrical flow path from the light incident surface of the flow cell 2, and is emitted from the light transmission surface. . Reference numeral 12 denotes a concave diffraction grating, and light that has passed through the flow cell 2 enters the diffraction grating 12 through the slit 14. Reference numeral 16 denotes a photodiode array element, which detects light dispersed by the diffraction grating 12 and sends it to the signal processing circuit 18.
[0004]
An image of the slit 14 by the light passing through the flow cell 2 is formed on the photodiode array 16 by the diffraction grating 12. On the photodiode array element 16, the light that has passed through the flow cell 2 is dispersed and condensed by the diffraction grating 12 to form a spectrum.
[0005]
[Problems to be solved by the invention]
The conventional absorbance detector as described above has a configuration in which a cell for inserting a sample and a slit are attached, and a diffraction grating as a spectroscopic means is further attached thereafter.
[0006]
In order to take this configuration, it is necessary to install the cell, the slit, the diffraction grating, and the photodetector separately, and to install them at a certain distance, and by reducing the installation space It was difficult to reduce the size of the apparatus. Further, since it was necessary to make optical adjustments among the four of the cell, the slit, the diffraction grating, and the photodetector, the adjustment was complicated.
[0007]
It is an object of the present invention to solve such problems and to provide an absorbance analyzer that can be adjusted relatively easily while reducing the size of the absorbance analyzer.
[0008]
[Means for Solving the Problems]
The absorbance detector according to the present invention, which has been made to solve the above problems, places a cell containing an analytical sample on a measurement optical path from a light source, separates the transmitted light from the cell by a dispersing means, and guides it to the photodetector. In the absorbance detector, a dispersion means is formed in the cell itself so as to form an image on the photodetector. In the absorbance detector of the present invention, since the cell itself is provided with the dispersion means, the transmitted light from the cell can be directly dispersed by this dispersion means, and therefore the optical system behind the cell is simplified and installed. Space can be miniaturized. In addition, adjustment between the cell and the diffraction grating is unnecessary, and adjustment between the slit, the cell, and the detector is sufficient.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of an absorbance detector used in a liquid chromatograph showing an embodiment of the present invention. In the figure, reference numeral 2 denotes a flow cell, in which a cylindrical flow path is formed as in the conventional example, and an effluent from a column to be analyzed flows. One end surface of the cylindrical flow path is a light incident surface of the spectroscopic optical system, and the other end surface is a light transmission surface. 4 is a light source, 6 is a lens, and 20 is a slit on the entrance side. Light from the light source 4 is condensed on the slit 20 by the lens 6. The slit 20 is attached close to the flow cell so that the light beam does not protrude from the cell width when the collected light passes through the cell. That is, most of the light collected by the slit 20 passes through the cylindrical flow path from the light incident surface of the flow cell 2 and is emitted from the light transmission surface of the cell so that the collected light is effectively used. Is arranged.
[0010]
As shown in the figure, the flow cell 2 has a transmissive spherical diffraction grating 2a formed on the light transmission side surface. The transmissive spherical diffraction grating 2a is formed by cutting a groove in a spherical surface using a photolithographic technique or the like in the same manner as a general diffraction grating forming method. The transmitted light of the flow cell 2 is dispersed and emitted when passing through the spherical diffraction grating 2a.
[0011]
A photodiode array 16 as a photodetector is installed behind the flow cell 2, and light can be detected for each wavelength by directly receiving each component of the light separated by the transmissive spherical diffraction grating 2a. . Accordingly, the optical system behind the flow cell 2 has only the photodiode array 16 at a certain distance.
[0012]
Then, the signal from the photodiode array 16 when the sample is not flowing in the flow cell 2 is stored in the storage device in the signal processing device 18 as reference data, and this data and the photodiode when the sample flows into the flow cell 2 are stored. Absorbance is calculated by performing a predetermined calculation based on the signal from the array.
[0013]
FIG. 3 is a block diagram of an absorbance detector used in a liquid chromatograph showing another embodiment of the present invention. In the flow cell 2 in this figure, a spherical lens 2b is formed on the light incident surface side, and a prism 2c is formed by the wall surface on the light transmitting surface side. That is, the light that has passed through the slit 20 forms a slit image that is spectrally separated on the rear photodiode array 16 by the spherical lens 2b and the prism 2c that is provided at an angle with the optical axis. Therefore, even in this case, as the optical system behind the flow cell 2, there is only the photodiode array 16 at a certain distance. FIG. 4 also shows another embodiment of the present invention. In the above embodiment, the slit 20 on the entrance side is provided in front of the cell so that the image of the slit 20 is formed on the photodiode array. However, instead of this, the light beam from the light source may be incident as parallel light and dispersed by a dispersive element provided on the transmission side of the cell. In this case, a flat surface is formed on the incident side of the cell, and a spherical diffraction grating 2d is formed on the transmission side of the cell. Further, by making the width of the parallel light flux sufficiently small, the necessary wavelength resolution can be obtained even if the transmission side of the cell is a plane diffraction grating or a prism.
[0014]
In the present embodiment, a flow cell through which a liquid flows is used.
[0015]
【The invention's effect】
As described above, in the absorbance detector of the present invention, since the cell itself is provided with a dispersion function and has a light collecting function, there is no need to install a dispersion element behind the cell, and the apparatus can be downsized. Can be achieved. Further, since the cell and the dispersion element are integrated, the number of adjustment parts is reduced, and the adjustment is simplified. Further, since the cell and the dispersive element are integrated, the positional relationship between them does not fluctuate and stable measurement is possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a conventional absorbance detector.
FIG. 2 is a configuration diagram of an absorbance detector according to an embodiment of the present invention.
FIG. 3 is a configuration diagram of an absorbance detector according to an embodiment of the present invention.
FIG. 4 is a configuration diagram of an absorbance detector according to an embodiment of the present invention.
[Explanation of symbols]
2: Flow cell 2a: Transmission type spherical diffraction grating (dispersing means)
2b: spherical lens 2c: prism (dispersing means)
2d: Transmission type spherical diffraction grating (dispersing means)
16: Photodiode array (photodetector)
20: Slit

Claims (1)

A cell in which an analysis sample is placed is placed on a measurement optical path from a light source, and a cell is formed so that an image is formed on the light detector in an absorbance detector that guides the light transmitted through the cell to a light detector after being dispersed by a dispersion means. Absorbance detector, characterized in that a dispersion means is formed in itself.

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