Analysis device and gain adjustment device

Abstract

To obtain a proper measurement result by a photomultiplier tube according to the density of a component included in a sample.SOLUTION: A high performance liquid chromatograph 1 comprises a photomultiplier tube 63 which detects fluorescence emitted from a sample and a gain adjustment device 7 which adjusts the gain of the photomultiplier tube 63. The gain adjustment device 7 includes an acquisition part 72 which acquires a detected value of the fluorescence by the photomultiplier tube 63, a power supply part 74 which supplies electric power to the photomultiplier tube 63, and a power supply control part 73 which controls the power supply part 74 according to the detection value that the acquisition part 72 acquires to adjust the gain of the photomultiplier tube 63 during a single analysis of the sample.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a gain adjustment device that adjusts the gain of a fluorescence detector and an analyzing device equipped with the gain adjustment device. [Background technology]

[0002] A fluorescence detector is one of the detectors used in high-performance liquid chromatography. The photomultiplier tube used in the fluorescence detector is capable of detecting weak light with high sensitivity.

[0003] When the sample concentration is high, the fluorescence intensity becomes strong and the output of the photomultiplier tube may become saturated. Therefore, when the sample concentration is high, it is necessary to reduce the gain of the photomultiplier tube to avoid saturation of the output. On the other hand, when the sample concentration is low, it is necessary to increase the gain of the photomultiplier tube so that the signal caused by the components is not buried in noise from the electrical system, etc.

[0004] The high-performance liquid chromatograph disclosed in the following Patent Document 1 includes a UV-VIS detector unit. This detector unit includes a configuration for detecting a reference beam that does not pass through a sample within the detector unit. This allows the fluctuation in the intensity of light output from a light source included in the detector unit to be obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2020-526770 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, in chromatographic impurity analysis, it is necessary to analyze both the main component in high concentration and the impurities in low concentration contained in one sample. However, as mentioned above, when analyzing a high concentration component, it is necessary to lower the gain of the photomultiplier tube, and when analyzing a low concentration component, it is necessary to increase the gain of the photomultiplier tube, so it was not possible to analyze these components at the same time. For this reason, measures such as sacrificing sensitivity and performing the analysis with a low gain setting, or changing the gain and performing two analyses are adopted.

[0007] An object of the present invention is to provide an analytical device that can obtain appropriate measurement results using a fluorescence detector according to the concentrations of components contained in a sample. [Means for solving the problem]

[0008] An analytical apparatus according to one aspect of the present invention includes a light source that excites a sample, a photomultiplier tube that detects fluorescence emitted from the sample, and a gain adjustment device that adjusts the gain of the photomultiplier tube. The gain adjustment device includes an acquisition unit that acquires a detection value of the fluorescence by the photomultiplier tube, a power supply unit that supplies power to the photomultiplier tube, and a power supply control unit that adjusts the gain of the photomultiplier tube during one analysis of the sample by controlling the power supply unit of the photomultiplier tube in accordance with the detection value acquired by the acquisition unit.

[0009] A gain adjustment device according to another aspect of the present invention is a gain adjustment device that adjusts the gain of a photomultiplier tube, and includes an acquisition unit that acquires a detection value of the photomultiplier tube, a power supply unit that supplies power to the photomultiplier tube, and a power supply control unit that adjusts the gain of the photomultiplier tube during one analysis of a sample by controlling the power supply unit in accordance with the detection value acquired by the acquisition unit. Effect of the Invention

[0010] According to the present invention, it is possible to provide an analytical device that can obtain appropriate measurement results using a photomultiplier tube according to the concentration of a component contained in a sample. [Brief description of the drawings]

[0011] [Figure 1] 1 is an overall view of a high-performance liquid chromatograph according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram of a fluorescence detector and a gain adjustment device according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing the fluorescence intensity input to a photomultiplier tube. [Figure 4] 1 is a graph showing a voltage applied to a photomultiplier tube. [Diagram 5] 1 is a graph showing detection values ​​output from a photomultiplier tube. [Figure 6] 13 is a graph showing corrected detection values. [Figure 7] 11 is a graph showing detection values ​​in a state where a high-concentration region is saturated. [Figure 8] 11 is a graph showing detection values ​​in a state where a low density region is buried in noise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, a gain adjustment device and an analysis device including the gain adjustment device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] (1) Overall configuration of the device 1 is an overall view showing a high performance liquid chromatograph 1 according to the present embodiment. The high performance liquid chromatograph 1 includes a solvent supply unit 2, a liquid delivery pump 3, a sample injection device 4, a column 5, a fluorescence detector 6, and a gain adjustment device 7. The high performance liquid chromatograph 1 is an example of the analytical device of the present invention.

[0014] The solvent supply unit 2 stores a solvent such as an aqueous solvent or an organic solvent. The liquid delivery pump 3 supplies the solvent stored in the solvent supply unit 2 to the analysis flow path as a mobile phase. The sample injection device 4 injects a sample into the solvent supplied to the analysis flow path. The solvent into which the sample has been injected is introduced into the column 5. In the column 5, components contained in the sample are separated based on the interaction between the mobile phase and the stationary phase. The sample separated in the column 5 is introduced into the fluorescence detector 6 together with the solvent. The fluorescence detector 6 irradiates the sample with excitation light and detects the fluorescence generated from the sample with a photomultiplier tube. The gain adjustment device 7 adjusts the gain of the fluorescence detector 6. The gain adjustment device 7 also corrects the detection value of the fluorescence detector 6 according to the gain of the fluorescence detector 6.

[0015] (2) Configuration of the fluorescence detector Next, the configuration of the fluorescence detector 6 will be described with reference to Fig. 2. The fluorescence detector 6 includes a light source 61, a flow cell 62, a photomultiplier tube (PMT) 63, and a current-voltage conversion circuit 64, as shown in Fig. 2.

[0016] The light source 61 irradiates the sample with excitation light. A xenon lamp, a deuterium lamp, or the like is used as the light source 61. The excitation light irradiated from the light source 61 is extracted by a spectrometer (not shown) as excitation light having a specific wavelength, and is irradiated onto the sample flowing in the flow cell 62.

[0017] A fluorescent sample flowing through the flow cell 62 is irradiated with excitation light, causing the sample to emit fluorescence. A spectrometer (not shown) selects a specific wavelength of the fluorescence emitted from the sample and the selected wavelength is incident on a photomultiplier tube 63.

[0018] The photomultiplier tube 63 receives the fluorescence emitted from the sample and generates electrons according to the intensity of the light through the photoelectric effect. The photomultiplier tube 63 then amplifies the generated electrons and outputs the detection value of the sample as an electrical signal.

[0019] The current-voltage conversion circuit 64 converts the current as the detection value output from the photomultiplier tube 63 into a voltage. The detection value of the sample converted into a voltage in the current-voltage conversion circuit 64 is output to the gain adjustment device 7.

[0020] (3) Configuration of gain adjustment device Next, the configuration of the gain adjustment device 7 will be described with reference to Fig. 2. As shown in Fig. 2, the gain adjustment device 7 includes a division unit 71, an acquisition unit 72, a power supply control unit 73, a power supply unit 74, and a gain calculation unit 75. The division unit 71 and the gain calculation unit 75 form a correction unit 70.

[0021] The correction unit 70 inputs the detection value of the sample output from the fluorescence detector 6. The correction unit 70 corrects the input detection value in accordance with the gain value (multiplication factor) of the photomultiplier tube 63. The correction unit 70 outputs the corrected detection value as the measurement value of the sample.

[0022] The acquisition unit 72 receives the corrected detection value output from the correction unit 70. The acquisition unit 72 provides the acquired corrected detection value to the power supply control unit 73.

[0023] The power supply control unit 73 controls the power supply unit 74. The power supply control unit 73 controls the power supply unit 74 based on the corrected detection value of the sample acquired from the acquisition unit 72. The power supply unit 74 is a high-voltage power supply that supplies power to the photomultiplier tube 63.

[0024] When the corrected detection value of the sample is higher than a first threshold, the power supply control unit 73 issues an instruction to the power supply unit 74 to reduce the voltage applied to the photomultiplier tube 63. For example, the power supply control unit 73 issues an instruction to the power supply unit 74 to reduce a predetermined voltage from the currently applied voltage. When the corrected detection value of the sample is lower than a second threshold, the power supply control unit 73 issues an instruction to the power supply unit 74 to increase the voltage applied to the photomultiplier tube 63. For example, the power supply control unit 73 issues an instruction to the power supply unit 74 to increase a predetermined voltage from the currently applied voltage.

[0025] The gain calculation unit 75 acquires the voltage value applied to the photomultiplier tube 63 by the power supply unit 74. The gain calculation unit 75 calculates the gain of the photomultiplier tube 63 based on the voltage value currently supplied by the power supply unit 74. The gain calculation unit 75 stores the relationship between the voltage applied to the photomultiplier tube 63 and the gain of the photomultiplier tube 63 as a table. The gain calculation unit 75 calculates the current gain of the photomultiplier tube 63 based on the stored table. The relationship between the applied voltage and the gain of the photomultiplier tube may vary from product to product. Therefore, the gain adjustment device 7 of this embodiment stores a table for the photomultiplier tube 63 attached to the fluorescence detector 6 in a storage device in advance. This table may be provided at the time of factory shipment, or may be obtained by measurement in the high performance liquid chromatograph 1 equipped with the fluorescence detector 6 and the gain adjustment device 7.

[0026] The gain of a photomultiplier tube can be expressed by the following formula: μ = A V kn In this formula, μ is the gain, V is the applied voltage, and A, k, and n are constants that depend on the circuit and the photomultiplier tube device.

[0027] The division unit 71 acquires the current gain of the photomultiplier tube 63 calculated by the gain calculation unit 75, and corrects the detection value of the sample based on the acquired gain. In this embodiment, the division unit 71 divides the detection value output from the fluorescence detector 6 by the gain, and outputs the corrected detection value.

[0028] (4) Gain adjustment method Next, a gain adjustment method according to this embodiment will be described with reference to Figs. 3 to 9. Graph SA shown in Fig. 3 indicates the fluorescence intensity input to the photomultiplier tube 63. Graph SA indicates the actual fluorescence intensity generated from the sample in the flow cell 62. Graph SA includes an area C1 indicating a high concentration component contained in the sample, and an area C2 indicating a low concentration component contained in the sample. For example, area C1 is a detection area for a main component contained in the sample, and area C2 is a detection area for an impurity contained in the sample.

[0029] Region C1 is a region showing a high concentration of components, and the fluorescence intensity is strong. Therefore, when the gain of the photomultiplier tube 63 is large, the detection value of the photomultiplier tube 63 may be saturated around region C1, as shown in FIG. 7. Region C2 is a region showing a low concentration of components, and the fluorescence intensity is weak. Therefore, when the gain of the photomultiplier tube 63 is small, the detection value of the photomultiplier tube 63 may be buried in noise NS caused by the electrical system, etc., around region C2, as shown in FIG. 8. Therefore, the gain adjustment device 7 of this embodiment adjusts the voltage applied to the photomultiplier tube 63 to prevent the detection value from being saturated or buried in noise.

[0030] Graph SB shown in FIG. 4 shows the change in voltage supplied to the photomultiplier tube 63. That is, graph SB shows the change in voltage applied from the power supply unit 74 to the photomultiplier tube 63. In this embodiment, the power supply unit 74 switches between two voltage levels, V1 and V2, and supplies the voltage to the photomultiplier tube 63. The photomultiplier tube 63 maintains a high gain when voltage V1 is applied, and reduces the gain when voltage V2 is applied. Voltage V1 is a voltage that is set so that low-concentration components can be detected with high sensitivity. Voltage V2 is a voltage that is set so that high-concentration components can be detected without saturation.

[0031] 3, the fluorescence intensity indicated by TH1 is the intensity at which the detection value of the first threshold value TH1 is output from the photomultiplier tube 63. Moreover, the fluorescence intensity indicated by TH2 is the intensity at which the detection value of the second threshold value TH2 is output from the photomultiplier tube 63.

[0032] As shown by the graph SA in FIG. 3, at time t1, the detection value exceeds the first threshold value TH1. When the power supply control unit 73 determines that the detection value received from the acquisition unit 72 exceeds the first threshold value TH1, it instructs the power supply unit 74 to reduce the voltage. As shown in FIG. 4, the voltage applied by the power supply unit 74 to the photomultiplier tube 63 is V1 at a stage before time t1. When the detection value exceeds the first threshold value TH1, the power supply control unit 73 sends an instruction to the power supply unit 74 to reduce the voltage from V1 to V2. The amount of voltage reduction may be set by the user.

[0033] 4, the voltage applied to the photomultiplier tube 63 by the power supply unit 74 does not instantly drop to voltage V2 at time t1. The applied voltage slowly drops for a while, and then drops to voltage V2. This is because the power supply unit 74, which is a high-voltage power supply, generally requires time to change the output voltage (for example, a time lag of about 100 milliseconds to 1 second is required).

[0034] As shown in FIG. 3, at time t2, the detection value is below the second threshold TH2. When the power supply control unit 73 determines that the detection value received from the acquisition unit 72 is below the second threshold TH2, it instructs the power supply unit 74 to increase the voltage. As shown in FIG. 4, after time t1, the voltage applied by the power supply unit 74 to the photomultiplier tube 63 is V2. When the detection value falls below the second threshold TH2, the power supply control unit 73 sends an instruction to the power supply unit 74 to increase the voltage from V2 to V1. The amount of increase in voltage may be set by the user.

[0035] As described above, the power supply unit 74, which is a high-voltage power supply, generally takes time to change the output voltage. Therefore, the voltage applied to the photomultiplier tube 63 by the power supply unit 74 does not instantly rise to voltage V1 at time t2. The applied voltage slowly drops for a while and then rises to voltage V1.

[0036] Graph SC shown in Fig. 5 shows changes in the detection value output from the photomultiplier tube 63. As graph SC shows, the detection value in region C1, which indicates a high concentration component, is kept lower than that in graph SA shown in Fig. 3. This is because the gain of the photomultiplier tube 63 is reduced by reducing the voltage applied to the photomultiplier tube 63 to V2 between time t1 and time t2. As a result, although the detection value in region C1, which indicates a high concentration component, is reduced, saturation of the detection value is avoided.

[0037] Graph SD shown in Fig. 6 shows the change in detection value after correction by the correction unit 70. Compared with graph SC in Fig. 5, it can be seen that the detection value in region C1 indicating high concentration components has been corrected. It can be seen that the graph SD shown in Fig. 6 has restored the shape of graph SA shown in Fig. 3. Since the correction unit 70 corrects the detection value according to the gain, it is possible to obtain an output signal that is similar to that when the gain is constant.

[0038] As shown in FIG. 3 to FIG. 6, in the region C2 of low concentration components contained in the sample, a correct detection value is obtained by supplying the voltage V1 to the photomultiplier tube 63. In other words, by maintaining the gain of the photomultiplier tube 63 high, low concentration components are also correctly detected without being buried in noise. In addition, in the region C1 of high concentration components contained in the sample, by supplying the voltage V2 lower than the voltage V1 to the photomultiplier tube 63, the detection value is detected without saturation. In other words, the gain of the photomultiplier tube 63 is reduced, and high concentration components are also correctly detected without saturation. Since the detection value is not saturated, if the actual gain of the photomultiplier tube 63 is known, the original fluorescence intensity can be restored by correction processing by the correction unit 70.

[0039] In this way, the gain adjustment device 7 of this embodiment corrects the detection value according to the voltage supplied by the power supply unit 74 to the photomultiplier tube 63. This makes it possible to correctly restore the detection value as the original analysis result while changing the gain of the photomultiplier tube 63 during one analysis of the sample. For example, it is also possible for the correction unit 70 to correct the detection value based on the timing of the voltage change instruction given by the power supply control unit 73 to the power supply unit 74. However, when such a method is adopted, a time lag occurs in the change in the voltage applied from the power supply unit 74, so that the detection value cannot be corrected accurately. In this embodiment, the actual gain of the photomultiplier tube 63 at each moment is estimated according to the change in the voltage actually supplied from the power supply unit 74, not based on the timing of the voltage change instruction given by the power supply control unit 73, and the detection value is corrected based on this, so that the detection value can be correctly corrected.

[0040] The gain adjustment device 7 of this embodiment adjusts the gain of the photomultiplier tube 63 during one analysis of a sample by the high performance liquid chromatograph 1. This makes it possible to obtain analysis results in one analysis even for a sample that contains high concentration components and low concentration components. Therefore, it is possible to virtually widen the dynamic range of the fluorescence detector 6 of this embodiment. It is no longer necessary to take measures such as changing the gain and performing two analyses as in the conventional method, and it is possible to improve the efficiency of the analysis process.

[0041] (5) Other embodiments In the above embodiment, the acquiring unit 72 is configured to input the detection value after correction by the correcting unit 70. In another embodiment, the acquiring unit 72 may input the detection value before correction by the correcting unit 70. In this case, the acquiring unit 72 may be configured to input the output value from the current-voltage conversion circuit 64. The power supply control unit 73 compares the detection value before correction with a threshold value and controls the power supply unit 74. In this case, it is necessary to set a threshold value according to the detection value before correction.

[0042] In the above embodiment, two thresholds, a first threshold TH1 and a second threshold TH2, are used. In another embodiment, a single threshold TH can be used. In this case, when the threshold TH is exceeded, the gain of the photomultiplier tube 63 is reduced, and when the threshold TH is below, the gain of the photomultiplier tube 63 is increased. However, when the detection value increases or decreases in a short period of time due to noise or other factors, the gain is frequently switched, so it is preferable to use two thresholds as in the above embodiment.

[0043] In the above embodiment, a high performance liquid chromatograph is used as an analytical device. The fluorescence detector 6 and the gain adjustment device 7 of the present embodiment can also be applied to a gas chromatograph, a mass spectrometer using a secondary electron multiplier, or other types of liquid chromatographs.

[0044] (6) Description It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0045] (Section 1) An analysis apparatus according to one embodiment includes: A light source for exciting the sample; a photomultiplier tube for detecting the sample; a gain adjustment device for adjusting the gain of the photomultiplier tube; Equipped with The gain adjustment device includes: an acquisition unit that acquires a detection value of the sample by the photomultiplier tube; a power supply unit for supplying power to the photomultiplier tube; a power supply control unit that adjusts a gain of the photomultiplier tube during one analysis of the sample by controlling the power supply unit of the photomultiplier tube in accordance with the detection value acquired by the acquisition unit; Includes.

[0046] Appropriate measurement results can be obtained using a photomultiplier tube depending on the concentration of the components contained in the sample.

[0047] (Section 2) 2. The analytical device according to claim 1, The gain adjustment device includes: a correction unit that corrects the detection value output from the photomultiplier tube in accordance with a gain of the photomultiplier tube; may include:

[0048] The detection value is corrected according to the gain of the photomultiplier tube, so appropriate measurement results can be obtained.

[0049] (Section 3) 3. The analysis device according to claim 2, The correction unit is a gain calculation unit that acquires a voltage value supplied to the photomultiplier tube by the power supply unit and calculates a gain of the photomultiplier tube based on the acquired voltage value; may include:

[0050] Since the detected value is corrected based on the voltage supplied from the power supply unit, appropriate measurement results can be obtained.

[0051] (Section 4) 2. The analytical device according to claim 1, The power supply control unit is When the detection value acquired by the acquisition unit exceeds a first threshold, an instruction to decrease a gain of the photomultiplier tube is given to the power supply unit, and when the detection value acquired by the acquisition unit falls below a second threshold, an instruction to increase a gain of the photomultiplier tube is given to the power supply unit.

[0052] This makes it possible to avoid frequent changes in voltage when, for example, the detected value fluctuates.

[0053] (Section 5) 3. The analysis device according to claim 2, The acquisition unit may acquire the detection value corrected by the correction unit.

[0054] Based on the corrected detection value, gain adjustment according to the concentration is possible.

[0055] (Section 6) 2. The analytical device according to claim 1, A fluorescent sample may be irradiated with excitation light, and the photomultiplier tube may detect the emitted fluorescence.

[0056] Appropriate gain adjustment is performed depending on the intensity of the fluorescence emitted from the sample.

[0057] (Section 7) 2. The analytical device according to claim 1, The gain adjustment device may adjust the gain of the photomultiplier tube included in the fluorescence detector.

[0058] Components can be detected with high sensitivity.

[0059] (Section 8) A gain adjustment device according to another aspect includes: A gain adjustment device for adjusting a gain of a photomultiplier tube, comprising: an acquisition unit that acquires a detection value of the photomultiplier tube; A power supply unit for supplying power to the photomultiplier tube; a power supply control unit that adjusts a gain of the photomultiplier tube during one analysis of a sample by controlling the power supply unit in response to the detection value acquired by the acquisition unit; Includes.

[0060] Appropriate measurement results can be obtained using a photomultiplier tube depending on the concentration of the components contained in the sample. [Explanation of symbols]

[0061] 1...High performance liquid chromatograph, 6...Fluorescence detector, 7...Gain adjustment device, 63...Photomultiplier tube, 70...Compensation unit, 71...Division unit, 72...Acquisition unit, 73...Power supply control unit, 74...Power supply unit, 75...Gain calculation unit

Claims

1. A light source for exciting the sample; a photomultiplier tube for detecting fluorescence emitted from the sample; a gain adjustment device for adjusting the gain of the photomultiplier tube; Equipped with The gain adjustment device includes: an acquisition unit that acquires a detection value of the fluorescence by the photomultiplier tube; a power supply unit for supplying power to the photomultiplier tube; a power supply control unit that adjusts a gain of the photomultiplier tube during one analysis of the sample by controlling the power supply unit of the photomultiplier tube in accordance with the detection value acquired by the acquisition unit; An analytical device comprising:

2. The gain adjustment device includes: a correction unit that corrects the detection value output from the photomultiplier tube in accordance with a gain of the photomultiplier tube; The analytical device of claim 1 .

3. The correction unit is a gain calculation unit that acquires a voltage value supplied to the photomultiplier tube by the power supply unit and calculates a gain of the photomultiplier tube based on the acquired voltage value; The analytical device of claim 2 .

4. The power supply control unit is 2. The analyzer according to claim 1, wherein when the detection value acquired by the acquisition unit exceeds a first threshold, an instruction to decrease a gain of the photomultiplier tube is given to the power supply unit, and when the detection value acquired by the acquisition unit falls below a second threshold, an instruction to increase a gain of the photomultiplier tube is given to the power supply unit.

5. The analyzer according to claim 2 , wherein the acquisition unit acquires the detection value after correction by the correction unit.

6. 2. The analytical device according to claim 1, wherein a fluorescent sample is irradiated with excitation light, and the photomultiplier tube detects the emitted fluorescence.

7. The analyzer according to claim 1 , wherein the gain adjustment device adjusts a gain of the photomultiplier tube included in a fluorescence detector.

8. A gain adjustment device for adjusting a gain of a photomultiplier tube, comprising: an acquisition unit that acquires a detection value of the photomultiplier tube; a power supply unit for supplying power to the photomultiplier tube; a power supply control unit that adjusts a gain of the photomultiplier tube during one analysis of a sample by controlling the power supply unit in response to the detection value acquired by the acquisition unit; A gain adjustment device including:

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