JP2016038208A - Optical detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical detector that can accomplish simultaneously and at high resolution optical measurement of a plurality of wavelengths while preventing a sample flowing in a flow cell from degenerating.SOLUTION: A light source device is provided with a plurality of light emitting diodes that emit light beams of mutually different wavelengths. An optical system is so configured as to guide light beams emitted from the light emitting diodes to a flow cell. An optical detector detects the intensity of the light beams from the flow cell. A controller is equipped with light source switching means that is so configured as to consecutively change over the light emitting diode emitting the light beam of the wavelength to be used for measurement at timings different from each other. An arithmetic processor is equipped with a change-over switch circuit that so switches over an arithmetic unit which captures detection signals of the optical detector in synchronism with the timing of light emitting diode switching over by the light source switching means that the arithmetic unit matching the wavelength of the light beam emitted from the light emitting diodes captures the detection signals of the optical detector at the time of irradiation of the flow cell with the light beam.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical detector used as a detector for detecting sample components separated in, for example, HPLC (high performance liquid chromatograph).

  A spectrophotometer is mentioned as an optical detector used as a detector for liquid chromatographs. The spectrophotometer includes a so-called pre-spectroscopy method and a so-called post-spectroscopy method.

  The spectrophotometer of the pre-spectrometer type places a rotatable spectroscope between the light source and the flow cell (on the front side of the flow cell), and irradiates the flow cell with light of a specific wavelength by adjusting the rotation angle of the spectroscope. The concentration of the specific component in the sample flowing through the flow cell is quantified by detecting the intensity of light transmitted through the flow cell or the intensity of fluorescence emitted from the sample in the flow cell by a photodetector ( For example, refer to FIG. 6 of Patent Document 1.)

  On the other hand, the spectrophotometer of the post-spectral method has a spectroscope disposed on the rear stage side of the flow cell, separates the light from the flow cell for each wavelength component by the spectroscope, and simultaneously detects these wavelength components by the photodiode array ( For example, refer to FIG.

JP 2012-220472 A

  In recent years, analysis using a liquid chromatograph has been accelerated, and an improvement in detection speed (resolution) of a detector has been demanded. The spectrophotometer of the post-spectral method has an advantage that the intensity of the light of the multi-wavelength component from the flow cell can be detected simultaneously by the photodiode array, but irradiates the flow cell with a strong energy light containing the multi-wavelength component. Therefore, depending on the sample, alteration of its components may occur.

  In the pre-spectral spectrophotometer, the flow cell is irradiated only with light having a specific wavelength component out of the light dispersed by the spectroscope, so that the problem of sample deterioration due to light energy applied to the sample is unlikely to occur. However, in order to perform optical measurement of multiple wavelengths simultaneously, it is necessary to switch the wavelength component of the light irradiated to the flow cell by driving the spectrometer at high speed, and the switching speed of the measurement wavelength is Because of this, there is a limit to improving the resolution of simultaneous measurement of multiple wavelengths.

  Accordingly, an object of the present invention is to provide an optical detector capable of simultaneously performing optical measurement for a plurality of wavelengths with high resolution while preventing deterioration of a sample flowing through a flow cell.

  An absorbance detector according to the present invention includes a flow cell for circulating a sample, a light source device including a plurality of light emitting diodes that emit light of different wavelengths, and light emitted from each light emitting diode as light on the same optical path to the flow cell. An optical system for guiding, a photodetector for detecting light from the flow cell, a control unit having light source switching means configured to light each light emitting diode continuously at different timings, and a photodetector. A calculation unit that performs a predetermined calculation based on the obtained detection signal is provided for each wavelength of light emitted from each light-emitting diode, and the light flows to the calculation unit corresponding to the wavelength of light emitted from the light-emitting diode. The timing of switching the light emitting diode by the light source switching means so that the detection signal of the photodetector when it is irradiated is captured An arithmetic processing unit having a switching circuit configured to switch the operation section taking the detection signal of the photodetector in synchronism, in which with a.

  In the present invention, the control unit has a plurality of light emitting diodes that emit light having different wavelengths, and the control unit is configured to continuously turn on the light emitting diodes at different timings. It is possible to irradiate only component light, and to prevent the sample flowing through the flow cell from being altered. Since the light emitting diode can be switched instantaneously between the lighting state and the extinguishing state, the wavelength of light irradiated to the flow cell can be switched at a higher speed than the wavelength switching by mechanical driving of the spectrometer. Further, the arithmetic processing unit has a calculation unit for each wavelength of light emitted from each light emitting diode, and light when the light is irradiated to the flow cell to the arithmetic unit corresponding to the wavelength of light emitted from the light emitting diode. Since it has a changeover switch circuit configured to switch the calculation unit that captures the detection signal of the photodetector in synchronization with the switching timing of the light emitting diode by the light source switching means so that the detection signal of the detector is captured, Optical measurements of wavelength can be made simultaneously and with high resolution.

It is a schematic block diagram which shows one Example of an optical detector. It is a block diagram which shows an example of the calculation control part of the Example. It is a timing chart which shows an example of the lighting timing of each light source part in the case of performing optical measurement of a sample simultaneously about 4 wavelengths, and the switching timing of the signal processing by a calculating means. It is a schematic block diagram which shows the other Example of an optical detector. It is a block diagram which shows an example of the calculation control part of the Example.

  In the present invention, the photodetector can be provided at a position for receiving light transmitted through the flow cell. Then, the absorbance of the sample flowing in the flow cell can be measured.

  The photodetector is provided at a position off the position on the optical axis of the light irradiated to the flow cell, and detects fluorescence emitted from the sample in the flow cell excited by the excitation light irradiated from the light emitting diode. It may be a thing. In that case, a fluorescent filter for removing the excitation light component is provided between the flow cell and the photodetector.

  There are manufacturing variations in light emitting diodes such as light emitting diodes, and the light emitted from the light emitting diodes may contain light of a wavelength other than the measurement wavelength. Therefore, it is preferable that a band pass filter having a transmission region in a narrower wavelength range than the light emitted from the light emitting diode is disposed on the light emitting side of the light emitting diode. If it does so, it can suppress that the light of an unnecessary wavelength range is irradiated to a flow cell, and can aim at prevention of quality change of a sample and improvement of measurement accuracy.

  One embodiment of an absorbance detector, which is one of optical detectors, will be described with reference to FIG.

  The absorbance detector includes a light source device 2 that can emit light having a plurality of wavelength components at different timings. The light emitted from the light source device 2 is applied to the flow cell 22 through which the sample flows, and the light transmitted through the flow cell 12 is received by the photodiode 22 (photodetector).

  The light source device 2 includes four light source units 4, 6, 8, and 10 that emit light having different wavelengths. The light source unit 4 emits light of a wavelength of 250 nm, the light source unit 6 of 260 nm, the light source unit 8 of 270 nm, and the light source unit 10 of light of 280 nm.

  The light source unit 4 is provided with a light emitting diode 4a that emits light having a wavelength of 250 nm. A band-pass filter 4b having a transmission characteristic in a wavelength range of 250 ± 4 nm is provided on the light-emitting side of the light-emitting diode 4a, and a collimation lens 4c for collimating light transmitted through the band-pass filter 4b is provided in front of the band-pass filter 4b. Yes. Since most of the light emitted from the light emitting diode 4a is light having a wavelength in the vicinity of 250 nm, the bandpass filter 4b is not necessarily provided. However, in this embodiment, in consideration of production variations of the light emitting diodes. Is provided. The same applies to the bandpass filters 6b, 8b and 10b of the light source units 6, 8 and 10.

  The light source unit 6 is provided with a light emitting diode 6a that emits light having a wavelength of 260 nm. A band-pass filter 6b having a transmission characteristic in a wavelength range of 260 ± 4 nm is provided on the light-emitting side of the light-emitting diode 6a, and a collimation lens 6c that converts the light transmitted through the band-pass filter 6b into parallel light is provided in front of the band-pass filter 6b. Yes.

  The light source unit 8 is provided with a light emitting diode 8a that emits light having a wavelength of 270 nm. A band-pass filter 8b having a transmission characteristic in a wavelength range of 270 ± 4 nm is provided on the light-emitting side of the light-emitting diode 8a, and a collimation lens 8c for collimating light transmitted through the band-pass filter 8b is provided in front of the band-pass filter 8b. Yes.

  The light source unit 10 is provided with a light emitting diode 10a that emits light having a wavelength of 280 nm. A band-pass filter 10b having a transmission characteristic in a wavelength range of 280 ± 4 nm is provided on the light-emitting side of the light-emitting diode 10a, and a collimation lens 10c for collimating the light transmitted through the band-pass filter 10b is provided in front of the band-pass filter 10b. Yes.

  The light source unit 4 is arranged to emit light from the light emitting diode 4 a toward the flow cell 12, and the light source units 6, 8, and 10 are perpendicular to the optical axis of light from the light source unit 4 to the flow cell 12. It arrange | positions so that the light from the light emitting diodes 6a, 8a, and 10a may be inject | emitted. Here, lighting the light source unit 4, 6, 8 or 10 means lighting each light emitting diode 4a, 6a, 8a or 10a.

  On the optical axis of the light from the light source unit 4 to the flow cell 12, half mirrors 14, 16, and 18 that form an optical system that guides the light from each of the light source units 4, 6, 8, and 10 to the flow cell 12 are disposed. The half mirrors 14, 16 and 18 are arranged obliquely with respect to the optical axis of the light from the light source unit 4. The half mirror 14 unites the optical axis of the light from the light source unit 6 with the optical axis of the light from the light source unit 4 and guides it to the flow cell 12. The half mirror 16 unites the optical axis of the light from the light source unit 8 with the optical axis of the light from the light source unit 4 and the light source unit 6 and guides it to the flow cell 12. The half mirror 18 unites the optical axis of the light from the light source unit 10 with the optical axes of the light from the light source unit 4, the light source unit 6, and the light source unit 8 and guides them to the flow cell 12.

  A photodiode 22 for detecting light transmitted through the flow cell 12 is provided on the opposite side of the light source unit 4 with the flow cell 12 interposed therebetween. A beam splitter 20 is provided between the half mirror 18 and the flow cell 12 to extract a part of light irradiated to the flow cell 12 from the light source unit 4, 6, 8 or 10 as reference light. A photodiode 25 (reference light detector) for detecting the reference light intensity is provided at a position for receiving the light extracted by the beam splitter 20.

  The detection signal of the photodiode 22 is taken into the arithmetic control unit 28 as a measurement signal through the amplifier 23 and the analog / digital converter (A / D converter) 24. The detection signal of the photodiode 25 passes through the amplifier 26 and the A / D converter 27 and is taken into the arithmetic control unit 28 as a reference signal.

  The arithmetic control unit 28 is based on signals from the light source switching means 29 and the photodiodes 22 and 25 as a control unit that controls switching on and off of the light source units 4, 6, 8, and 10 of the light source device 2. Computation means 30 is provided as a computation processing unit for obtaining the absorbance of the sample flowing through the flow cell 12.

  The light source switching means 29 is configured to switch the light emitting diodes 4a, 6a, 8a and 10a between the on state and the unlit state so that the wavelength of light applied to the flow cell 12 can be continuously switched. Each of the light emitting diodes 4a, 6a, 8a and 10a is turned on when a necessary current is applied from the LED drivers 32, 34, 36 and 38 provided correspondingly. Each LED driver 32, 34, 36 and 38 supplies a necessary current to each light emitting diode 4a, 6a, 8a and 10a based on a lighting or extinguishing signal given from the arithmetic control unit 28, or stops the supply of current. To do.

  An example of the configuration of the arithmetic control unit 28 will be described with reference to FIG.

  The arithmetic control unit 28 is provided corresponding to each wavelength in order to calculate the absorbance for each wavelength of the light irradiated to the flow cell 12 and the time division control circuit 40 that constitutes the light source switching means 29 (see FIG. 1). Calculation unit 44a-44d, changeover switch circuit 42a for distributing the reference signal to each calculation unit 44a-44d, changeover switch circuit 42b for distributing the measurement signal to each calculation unit 44a-44d, and measurement obtained by each calculation unit 44a-44d A communication unit 52 that outputs a value is provided. The reference signal is a signal obtained by amplifying the detection signal obtained by the photodiode 25 by the amplifier 26 and digitally processing it by the A / D converter 27. The measurement signal is a signal obtained by amplifying the detection signal obtained by the photodiode 22 by the amplifier 23 and digitally processing the signal by the A / D converter 24.

  The time division control circuit 40 sends a lighting signal or a light-off signal to the LED drivers 32, 34, 36, and 38 that drive the light emitting diodes 4a, 6a, 8a, and 10a so that the light emitting diodes that are turned on are continuously switched. It is a circuit configured to be given in a time division manner. The time division control circuit 40 outputs a switching signal to the changeover switch circuits 42a and 42b at the timing of switching the light source to be lit.

  The change-over switch circuits 42a and 42b, based on the switching signal from the time-division control circuit 40, have a calculation unit that executes a calculation process for obtaining absorbance based on the measurement signal and the reference signal between the calculation units 44a-44d. This is a circuit that switches in synchronization with the switching of the wavelength of the light that is irradiated onto the light.

  The calculation units 44a to 44d are provided corresponding to the wavelengths of light emitted from the light source units 4, 6, 8 and 10, respectively. The computing unit 44a corresponds to light having a wavelength of 250 nm, the computing unit 44b corresponds to light having a wavelength of 260 nm, the computing unit 44c corresponds to light having a wavelength of 270 nm, and the computing unit 44d corresponds to light having a wavelength of 280 nm. The change-over switches 42a and 42b receive the reference signal and the measurement signal obtained when the light source unit 4 (light emitting diode 4a) is turned on, and the reference signal obtained when the light source unit 6 (light emitting diode 6a) is turned on. The measurement signal is taken into the calculation unit 44b, and the reference signal and the measurement signal obtained when the light source unit 8 (light emitting diode 8a) is turned on are taken into the calculation unit 44c and obtained when the light source unit 10 (light emitting diode 10a) is turned on. The reference signal and the measurement signal are distributed to the calculation units 44a to 44d so that the reference signal and the measurement signal thus received are taken into the calculation unit 44d.

Each of the calculation units 44a to 44d is a digital filter 46 for removing high frequency components of the reference signal and the measurement signal, and a value obtained by dividing the measurement signal I passed through the digital filter 46 by the reference signal I ₀ passed through the digital filter 46 (I / I ₀₎ dividing section 48 for obtaining _{the, -log 10 (I / I 0} ) comprises the absorbance calculation section 50 for obtaining the, -log ₁₀ obtained by the absorbance calculation section 50 (I / I ₀ as absorbance ) Is output as a measurement value to an external monitor or the like via the communication unit 52. The calculation units 44a to 44d constitute the calculation processing means 30 (see FIG. 1).

  The time division control circuit 40, the changeover switch circuits 42a and 42b, and the calculation units 44a to 44d of the calculation control device 28 can be realized by software. The time division control circuit 40, the changeover switch circuits 42a and 42b, and the communication unit 52 may be realized by hardware, and the calculation units 44a to 44d may be realized by software.

  FIG. 3 shows an example of the timing of turning on or off each of the light source units 4, 6, 8, and 10 and the switching timing of the arithmetic unit that takes in the reference signal and the measurement signal. In FIG. 3, when the input signal of each wavelength is on, the reference signal and the measurement signal are taken into the calculation unit corresponding to the wavelength, and when the input signal is off, the reference signal and the measurement signal are input to the calculation unit corresponding to the wavelength. It means that it will not be captured.

  In this example, after the measurement is started, the light source unit 4 is turned on, and after a certain time has elapsed, the light source unit 4 is turned off to turn on the light source unit 6, and after a certain time has passed, the light source unit 6 is turned off. The light source unit 8 is turned on, and the light source unit 10 is turned on after a predetermined time has passed. After the light source unit 10 is turned on for a certain time, the light source unit 10 is turned off and the light source unit 4 is turned on. The cycle from turning on the light source unit 4 to turning off the light source unit 10 is defined as one cycle, and this cycle is continuously repeated during measurement. The time required for one cycle is, for example, 25 milliseconds.

  The signals obtained by the photodiodes 22 and 25 during the measurement are a reference signal and a measurement signal of light having a wavelength of 250 nm when the light source unit 4 is lit, and a wavelength of 260 nm when the light source unit 6 is lit. As a light reference signal and a measurement signal, a light reference signal and a measurement signal having a wavelength of 270 nm when the light source unit 8 is turned on, and as a light reference signal and a measurement signal having a wavelength of 280 nm when the light source unit 10 is turned on. It is processed as a measurement signal, and the absorbance for each wavelength is obtained in the computing units 44a-44d corresponding to each wavelength.

  Next, an embodiment of a fluorescence detector as an optical detector will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location which is the same structure as the light absorbency detector of FIG. 1, and description about the structure is abbreviate | omitted.

  This fluorescence detector includes a light source device 2 having the same configuration as the absorbance detector of FIG. The sample in the flow cell 12 is irradiated with light having wavelengths of 250 nm, 260 nm, 270 nm, and 280 nm emitted from the light source units 4, 6, 8, and 10 of the light source device 2 as excitation light, and fluorescence emitted from the excited sample is emitted. Detection is performed by the photodiode 22a. The photodiode 22a is arranged in a direction to receive the component in the direction perpendicular to the optical axis of the excitation light irradiated to the flow cell 12 out of the light emitted from the flow cell 12.

  A fluorescent filter 54 is provided between the flow cell 12 and the photodiode 22a. The fluorescence filter 54 has a characteristic of cutting light having a wavelength shorter than the longest wavelength (for example, 290 nm) of the excitation light so as to remove the excitation light component from the light from the flow cell 12 and extract the fluorescence component. It is a filter having.

  A detection signal of the photodiode 22a, which is a photo detector for measurement, is taken into the arithmetic control unit 28a as a measurement signal through the amplifier 23a and the A / D converter 24a. A detection signal of the photodiode 25 as a reference photodetector is taken into the arithmetic control unit 28a as a reference signal through the amplifier 26 and the A / D converter 27.

  Similar to the calculation control unit 28 in the embodiment of FIG. 1, the calculation control unit 28a includes a light source switching unit 29a and a calculation processing unit 30a. The light source switching unit 29a is configured to continuously switch the light source that emits the excitation light between the light source units 4, 6, 8, and 10, and the arithmetic processing unit 30a sends the detection signals of the photodiodes 22a and 25 to the light source unit. The fluorescence intensity when excitation light of each wavelength is irradiated on the flow cell 12 is obtained in synchronization with the timing of turning on / off the light sources 4, 6, 8, and 10.

  FIG. 5 shows an example of a specific configuration of the arithmetic control unit 28a, which is substantially the same as the configuration of the arithmetic control unit 28 (see FIG. 2) in the embodiment of FIG. The calculation control unit 28a is a calculation processing unit 30a for obtaining the fluorescence intensity when the flow cell 12 is irradiated with the excitation light of each wavelength, and the calculation units 45a-45d corresponding to the light source units 4, 6, 8, and 10 are used. It has. The wavelength of the excitation light is switched in a time division manner by the time division control circuit 40 as the light source switching means 29a, and the arithmetic unit that takes in the reference signal and the measurement signal is synchronized with the switching of the wavelength of the excitation light by the changeover switch circuits 42a and 42b. Can be switched.

  Each calculation unit 45a-45d includes a digital filter 46, a division unit 48, and a fluorescence calculation unit 50a, and finally the value as the fluorescence intensity calculated by the fluorescence calculation unit 50a is sent to an external monitor or the like via the communication unit 52. Is output.

  In the above embodiment, the configuration in which the four light source units 4, 6, 8, and 10 are switched in a time division manner has been described. However, the present invention is not limited to this, and two, three, or five or more are provided. You may make it switch a light source part by a time division.

2 Light source device 4, 6, 8, 10 Light source part 4a, 6a, 8a, 10a Light emitting diode (light emitting diode)
4b, 6b, 8b, 10b Band pass filter 4c, 6c, 8c, 10c Collimation lens 12 Flow cell 14, 16, 18 Half mirror 20 Beam splitter 22, 22a, 25 Photo diode 23, 23a, 26 Amplifier 24, 24a, 27 Analog / Digital converter 28, 28a Arithmetic controller 29, 29a Light source switching means 30, 30a Arithmetic means 32, 34, 36, 38 LED driver 40 Time division control circuit 42a, 42b Changeover switch circuit 44a-44d, 45a-45d Arithmetic unit 46 Digital filter 48 Division unit 50 Absorbance calculation unit 50a Fluorescence calculation unit 52 Communication unit

Claims (4)

A flow cell for circulating the sample;
A light source device including a plurality of light emitting diodes that emit light of different wavelengths;
An optical system for guiding light emitted from each of the light emitting diodes to the flow cell as light on the same optical path;
A photodetector for detecting light from the flow cell;
A control unit having light source switching means configured to continuously turn on each of the light emitting diodes at different timings;
A calculation unit that performs a predetermined calculation based on a detection signal obtained by the photodetector is provided for each wavelength of light emitted from each of the light emitting diodes, and the wavelength of the light emitted from the light emitting diodes. The photodetector is synchronized with the switching timing of the light emitting diodes by the light source switching means so that the detection signal of the photodetector when the light is irradiated to the flow cell is input to the corresponding arithmetic unit. And an arithmetic processing unit provided with a changeover switch circuit for switching a calculation unit that captures the detection signal of the optical detector.   The optical detector according to claim 1, wherein the photodetector is provided at a position for receiving light transmitted through the flow cell. The light detector is provided at a position deviating from a position on the optical axis of light irradiated to the flow cell, and emits fluorescence emitted from a sample in the flow cell excited by excitation light irradiated from the light emitting diode. Is to detect,
The optical detector according to claim 1, wherein a fluorescence filter that removes an excitation light component is provided between the flow cell and the photodetector.   4. The absorbance detector according to claim 1, wherein a band-pass filter having a transmission region with a narrower wavelength range than the light emitted from the light emitting diode is disposed on the light emitting side of the light emitting diode.

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