JP2003014720A - High-performance liquid chromatograph detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid chromatograph detector having a large S / N, a sufficient dynamic range, and capable of high-sensitivity detection. A mobile phase and a sample reach a measurement channel, are irradiated with monochromatic light from a spectroscope, detected by a detection element, and a detection signal is sent to a control unit. Further, the light moves to the measurement channel 17, is irradiated with monochromatic light from the spectroscope 3, and is detected by the detection element 12. The controller 19 calculates the time required for the mobile phase and the sample to move from the measurement channel 16 to the measurement channel 17 based on the pumping speed of the pump and the internal volume of the measurement channel 16. The detection signal obtained by the detection element 13 is added to the detection signal obtained by the detection element 12 after a time required for the mobile phase and the sample to move from the measurement flow path 16 to the measurement flow path 17 and divided by two. Then, the control unit 19 calculates an average value.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow-through type detector used in a liquid chromatograph for separating and analyzing components contained in a liquid. 2. Description of the Related Art FIG. 2 shows a basic configuration of a high performance liquid chromatograph. In this chromatograph, a mobile phase 21 contained in a container 20 is supplied to a column 24 via an injector 23 at a predetermined flow rate by a pump 22,
After passing through 4, the light is discharged through a detector 25. The sample is instantaneously injected from the injector 23, and each component is separated while passing through the column 24 and sent to the detector 25. The detector 25 detects the concentration of each component eluted from the column 24 and generates a detection signal. Each peak in the detection signal corresponds to each component of the sample, and the content of each component is determined by performing data processing (quantitative calculation) based on the detection signal. FIG. 3 shows a configuration of a flow-through type ultraviolet spectrophotometer used as the detector 25. Ultraviolet light from the light source 31 enters the spectroscope 34 and is separated by the diffraction grating 35, and only monochromatic light of a predetermined wavelength is irradiated on the flow cell 36. Here, the wavelength of the monochromatic light applied to the flow cell 36 is set by controlling the angle of the diffraction grating 35 by the pulse motor 39. The wavelength of the monochromatic light is selected so as not to be absorbed by the mobile phase and to exhibit a large absorbance for the sample. The mobile phase and the sample that have passed through the column 24 flow through the flow cell 36. The mobile phase and the sample flowing in the flow cell 36 are irradiated with monochromatic light,
After being absorbed by the sample in the flow cell 36, it is detected by the detection element 38. The detection signal output from the detection element 38 is input to the control unit 40, and the content of each component contained in the sample is determined from the detection signal. [0004] Although the conventional high-performance liquid chromatograph detector is configured as described above, the detection signal obtained from the eluted component contains a noise component. The strength of the detection signal depends on the physical properties of the eluted components, and it is necessary to increase the signal strength or reduce noise to increase the sensitivity of the detector. That is, it is necessary to increase S / N. To increase the signal intensity, it is necessary to increase the light amount of the light source, but at the same time, the noise also increases.
As a result, the S / N does not increase. By increasing the optical path length of the monochromatic light irradiated on the flow cell in the flow cell, the S / N is improved, but the amount of absorption by the sample component increases, and the amount of light reaching the detector decreases. The dynamic range cannot be obtained. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a detector for a liquid chromatograph having a large S / N, a sufficient dynamic range, and capable of high sensitivity detection. With the goal. [0007] In order to solve the above problems, a detector for a liquid chromatograph of the present invention comprises: a plurality of detecting means arranged in series along a flow path of a flow cell;
The apparatus includes means for correcting a time difference between a sample passing through these detecting means, and means for averaging detection signals from these detecting means after correcting the time difference. In general, by performing averaging n times,
S / N is improved by √ (n) times. Therefore, n detectors are arranged in series along the flow channel of the flow cell, and in each of the detectors, the same sample is measured in the same state, so that the time difference in which the sample passes through these detectors is corrected. Thereafter, the detection signals from these detection means are averaged. The noise can be reduced by ノ イ ズ (n) times by the averaging, so that the S / N can be reduced without reducing the light amount.
(N) times larger, the S / N is large, and high sensitivity detection is possible while maintaining a sufficient dynamic range. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of one embodiment when a flow-through type ultraviolet spectrophotometer is used as a detecting means. This flow-through type ultraviolet spectrophotometer is used as the detector 25 of the high-performance liquid chromatograph shown in FIG. The flow-through type ultraviolet spectrophotometer according to the present invention includes two sets of light sources 1 and 7, spectroscopes 3 and 8, diffraction gratings 4 and 9, pulse motors 5 and 10, and detection elements 12 and 1.
3 having a flow channel 15 having measurement channels 16 and 17
And a control unit 19. The mobile phase 21 is supplied to the column 24 through the injector 23 at a predetermined flow rate by the pump 22, and after passing through the column 24, is discharged through the flow-through type ultraviolet spectrophotometer. The sample injected from the injector 23 is separated by the column 24 and reaches a flow-through type ultraviolet spectrophotometer. The ultraviolet light from the light sources 1 and 7 is
8, the light is split by the diffraction gratings 4 and 9, and only monochromatic light of a predetermined wavelength is measured.
7 is irradiated. Here, the wavelength of the monochromatic light applied to the flow cell 15 is controlled by the
It is set by controlling the angles of the diffraction gratings 4 and 9 at 0. The wavelength of the monochromatic light is selected so as not to be absorbed by the mobile phase and to exhibit a large absorbance for the sample. The mobile phase 21 and the sample that have passed through the column 24 reach the measurement channel 16 of the flow cell 15 and are irradiated with monochromatic light from the spectroscope 8, and the monochromatic light is absorbed by the sample in the measurement channel 16. Thereafter, the detection signal is detected by the detection element 13 and a detection signal is sent to the control unit 19. Further, the mobile phase 21 and the sample move to the measurement channel 17 of the flow cell 15 and
After the monochromatic light is irradiated by the sample and the monochromatic light is absorbed by the sample in the measurement channel 17, the monochromatic light is detected by the detection element 12 and a detection signal is sent to the control unit 19. Photomultipliers are used as the detection elements 12 and 13. Measurement channel 16
And the measurement channel 17 are manufactured to have the same optical path length. The controller 19 calculates the time required for the mobile phase and the sample to move from the measurement channel 16 to the measurement channel 17 based on the liquid sending speed of the pump 22 and the internal volume of the measurement channel 16.
This time is stored in the control unit 19, and the detection signal obtained by the detection element 13 and the detection signal obtained by the detection element 12 after the time necessary for the mobile phase and the sample to move from the measurement channel 16 to the measurement channel 17 are obtained. The control unit 19 calculates the average value by adding the detection signal and dividing by two. Over the entire measurement time, the signals from the two detection elements 12 and 13 are thus acquired, the position is determined by the calculation time, and the average value is calculated. Further, a delay circuit is provided in the control unit 19 to determine the position for taking in the signals from the detection elements 12 and 13, and an average of the signal from the detection element 12 and the signal from the detection element 12 delayed by a predetermined time is provided. You can also calculate. The time required for the mobile phase 21 and the sample to move from the measurement flow path 16 to the measurement flow path 17 is calculated, and the position for taking in the signals obtained by the detection elements 12 and 13 is determined in consideration of the time difference. Since the measurement channel 16 and the measurement channel 17 are formed to have the same optical path length, the detection elements 12 and 13 always measure the same elution components in the same state. By averaging the two signals obtained in this way, the S / N of the detection signal is increased by √ (2) times. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes may be made within the scope of the present invention described in the appended claims. be able to. For example, a flow-through type ultraviolet spectrophotometer is used as the detection means, but other detection means generally used in liquid chromatography, such as a fluorescence detector, a differential refractometer, and an electrochemical detector, are used. be able to. Also, the time required for the mobile phase 21 and the sample to move from the measurement channel 16 to the measurement channel 17 is determined by the pump 2
2 is calculated from the liquid sending speed and the internal volume of the measurement flow channel 16, but is determined by measuring the difference in the detection time of the peak apex of the peaks of the elution components detected by the detection elements 12 and 13. You can also. According to the present invention, n detection means are arranged in series along the flow path of the flow cell, and after correcting the time difference between the passage of the sample through these detection means, the detection is performed. Since the detection signals from the means are averaged, the S / N can be increased by a factor of √ (n) without attenuating the light amount, and the S / N can be increased while maintaining a sufficient dynamic range.
/ N is large, enabling high sensitivity detection.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of one embodiment of a flow-through type ultraviolet spectrophotometer used as a detector for a liquid chromatograph of the present invention. FIG. 2 is a schematic configuration diagram of a conventional liquid chromatograph. FIG. 3 is a schematic configuration diagram of a conventional flow-through type ultraviolet spectrophotometer. [Description of Signs] 1, 7 --- Light source 3, 8 --- Spectroscope 4, 9 --- Diffraction grating 5, 10 --- Pulse motor 12, 13 --- Detector 15 --- Flow cell 16 , 17 --- Measurement channel 19 --- Control unit

Claims (1)

1. A high-performance liquid chromatograph detector having a flow cell, comprising: a plurality of detection means arranged in series along a flow path of the flow cell; and detection signals from the detection means. And means for averaging after correcting the time difference.