Calibration curve liquid production system, measurement system, and calibration curve liquid production method

Abstract

To easily create a calibration curve with which it is possible to obtain a more accurate TOC concentration.SOLUTION: Provided is a calibration curve liquid manufacturing system that manufactures a calibration curve liquid for creating a calibration curve and supplies it to a measurement device that measures the total organic carbon concentration of the liquid to be analyzed, by using the calibration curve. The calibration curve liquid manufacturing system comprises an analyte liquid line 100 that transports an analyze liquid to a TOC meter 500, a standard liquid line 110 that transports a standard liquid 210 to the analyte liquid line 100, and a mixing unit 400 that is provided to the analyte liquid line 100 and that mixes a diluent and the standard liquid 210 together to dilute the standard liquid 210. The mixture of the diluent and the standard liquid 210 having been mixed by the mixing unit 400 is supplied as a calibration curve liquid to the TOC meter 500.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a calibration curve liquid producing system, a measurement system, and a calibration curve liquid producing method. [Background technology]

[0002] Generally, the concentration of total organic carbon (TOC) contained in liquids is controlled using a total organic carbon meter. The calibration curve used in this meter is created using a standard solution.

[0003] As a total organic carbon meter for measuring TOC concentration (low concentration), a device that prepares a low concentration test solution inside the total organic carbon meter has been considered (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3265830 Summary of the Invention [Problem to be solved by the invention]

[0005] Commonly used calibration curves are created using standard solutions with high TOC concentrations. If a calibration curve created using a standard solution with a high TOC concentration is used to measure a low TOC concentration, the error rate in the high concentration range will be larger in the low concentration range, making it impossible to accurately determine the TOC concentration. Therefore, for total organic carbon analyzers that measure the TOC concentration in ultrapure water, a calibration curve must be created using a standard solution with a concentration equivalent to the low TOC concentration in ultrapure water. Meanwhile, the lower the concentration of the standard solution, the greater the influence of environmental contamination and human error in the preparation of the standard solution. Furthermore, the device described in Patent Document 1 obtains a low organic concentration by distilling the sample, which requires equipment such as a combustion tube and a heating furnace. This requires dedicated equipment, which is time-consuming and expensive.

[0006] An object of the present invention is to provide a calibration curve liquid preparation system, a measurement system, and a calibration curve liquid preparation method that can easily prepare a calibration curve that enables more accurate determination of TOC concentration. [Means for solving the problem]

[0007] The calibration curve solution producing system of the present invention comprises: A calibration curve liquid producing system that produces and supplies a calibration curve liquid for producing a calibration curve to a measuring device that measures the total organic carbon concentration of a liquid to be analyzed using the calibration curve, a first liquid delivery line that delivers a diluent to the measurement device; a second liquid transfer line for transferring a standard solution to the first liquid transfer line; a mixing unit provided in the first liquid sending line, which mixes the dilution liquid and the standard solution to dilute the standard solution; The mixture of the dilution solution and the standard solution mixed in the mixing section is supplied to the measuring device as the calibration curve solution.

[0008] The measurement system of the present invention also includes: A calibration curve liquid producing system that produces and supplies a calibration curve liquid for producing a calibration curve to a measuring device that measures the total organic carbon concentration of a liquid to be analyzed using the calibration curve, a first liquid delivery line that delivers a diluent to the measurement device; a second liquid transfer line for transferring a standard solution to the first liquid transfer line; a mixing unit provided in the first liquid sending line, which mixes the dilution liquid and the standard solution to dilute the standard solution; a calibration curve liquid producing system that supplies the mixed solution of the dilution liquid and the standard solution mixed in the mixing unit to the measurement device as the calibration curve liquid; The measuring device.

[0009] Further, the method for producing a calibration curve solution of the present invention comprises the steps of: 1. A method for producing a calibration curve liquid, the method comprising: producing and supplying a calibration curve liquid for preparing a calibration curve to a measuring device that measures the total organic carbon concentration of a liquid to be analyzed using the calibration curve; diluting the standard solution by mixing the dilution solution sent to the first liquid sending line to the measurement device with the standard solution sent to the first liquid sending line from a second liquid sending line for sending a standard solution; The mixed solution of the diluted solution and the standard solution is supplied to the measuring device as the calibration curve solution. [Effects of the Invention]

[0010] In the present invention, a calibration curve that enables more accurate determination of TOC concentration can be easily prepared. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an embodiment of a calibration curve solution producing system of the present invention; [Figure 2] 2 is a diagram for explaining an example of a method by which the correction unit shown in FIG. 1 corrects the calibration curve. FIG. [Figure 3] FIG. 10 is a diagram showing an example of output values ​​when a calibration curve is created in a high TOC concentration range. [Figure 4]FIG. 10 is a diagram showing an example of output values ​​when a calibration curve is created in a low TOC concentration range. [Figure 5] 1 is a diagram showing an application example of the calibration curve solution producing system of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing one embodiment of a calibration curve liquid production system of the present invention. As shown in FIG. 1, the calibration curve liquid production system according to this embodiment includes an analysis liquid line 100, a standard liquid line 110, a pump 300, a mixing unit 400, and a control unit 600. The calibration curve liquid mixed in the mixing unit 400 of this calibration curve liquid production system is supplied to a TOC meter 500. A correction unit 700 may be connected to the TOC meter 500 or may be provided inside the TOC meter 500. In addition, a flow meter 40 is provided in the analysis liquid line 100 to measure the flow rate of the analysis liquid sent to the analysis liquid line 100. The TOC meter 500 may also be included as one of the components of the calibration curve liquid production system.

[0013] The analysis liquid line 100 is a first liquid supply line that supplies the analysis liquid (e.g., ultrapure water in this embodiment) to the TOC analyzer 500. The ultrapure water supplied to the TOC analyzer 500 may be, for example, at least a portion of the ultrapure water supplied to a point of use from an ultrapure water production system including a pretreatment device, a primary pure water production system, and a secondary pure water production system (subsystem), or it may be ultrapure water stored in a predetermined storage tank. The analysis liquid supplied to the analysis liquid line 100 is used as a diluent for diluting a standard solution 210, which will be described later. The diluent supplied to the analysis liquid line 100 is not limited to the analysis liquid, and may be ultrapure water that is not the target of analysis. In this case, the analysis liquid and a diluent different from the analysis liquid may be supplied from different pipes.

[0014] The pump 300 pumps the standard solution 210 stored in the container 200. In this embodiment, the pump 300 requires stable and accurate liquid delivery speed. The pump 300 is preferably one that minimizes TOC elution from the liquid-contacting portion. The pump 300 is preferably, for example, a double-plunger type, but is not limited to this. The pump 300 may be any other type of pump as long as it has the same function. The pumping speed at which the pump 300 pumps the standard solution 210 from the container 200 (in other words, the liquid delivery speed at which the pump 300 delivers the standard solution 210 from the container 200 to the analysis target liquid line 100 via the second liquid delivery line, the standard solution line 110) is controlled based on the liquid delivery speed at which the analysis target liquid line 100 delivers ultrapure water and the TOC concentration of the standard solution 210. This control will be described later. The standard solution 210 may be prepared by diluting a standard solution (potassium hydrogen phthalate) linked to an international standard, or may be prepared by diluting an organic substance actually contained in ultrapure water, such as a urea solution. The standard solution line 110 sends the standard solution 210 pumped up by the pump 300 to the analysis target liquid line 100.

[0015] The mixer 400 mixes the standard solution 210 pumped up by the pump 300 with the ultrapure water sent from the analysis target liquid line 100. In this way, the mixer 400 dilutes the standard solution 210 pumped up by the pump 300 with the ultrapure water sent from the analysis target liquid line 100. A mixing coil may be used as the mixer 400. The liquid mixed by the mixer 400 is supplied to the TOC meter 500 as a calibration curve liquid.

[0016] The control unit 600 controls the pumping speed of the pump 300 for the standard solution 210 (the amount of the standard solution 210 supplied from the pump 300). The control unit 600 controls the pumping speed of the pump 300 for the standard solution 210 based on the liquid delivery speed of the ultrapure water and the TOC concentration of the standard solution 210 so that the TOC concentration of the liquid after mixing by the mixer 400 is equal to or less than a predetermined value. For example, if the liquid delivery speed (flow rate) of the ultrapure water in the analysis target liquid line 100 is 1000 mL / min, the TOC concentration of the standard solution 210 is 100 ppb-C, and the TOC concentration of the liquid after mixing by the mixer 400 is desired to be in the low concentration range (0.1 ppb-C + the TOC concentration of the ultrapure water), the control unit 600 controls the pump 300 so that the pump 300 pumps the standard solution 210 at a pumping speed of 1 mL / min. In this manner, the control unit 600 controls the pumping speed at which the pump 300 pumps the standard solution 210 from the container 200 so that it is equal to or less than a predetermined ratio (e.g., 1 / 100) of the liquid delivery speed at which the analysis target liquid line 100 delivers ultrapure water. This results in a dilution ratio of the standard solution 210 with ultrapure water of a predetermined ratio (e.g., 100 times) or greater. By diluting the standard solution 210, even if there is contamination or concentration error in the standard solution 210, the higher the dilution ratio, the smaller the contribution of such contamination or concentration error, allowing for the preparation of a standard solution with a more accurate concentration. Note that the standard solution 210 may have a TOC concentration higher than 100 ppb-C. In this case, the control unit 600 controls the pumping speed of the pump 300 to be slower than 1 mL / min. Furthermore, when the pump 300 has a fixed pumping speed (performance) of the standard solution 210, the TOC concentration of the standard solution 210 is adjusted so that the TOC concentration of the liquid after mixing by the mixer 400 is equal to or lower than a predetermined value. The control unit 600 has at least the function of stopping or operating the pumping operation of the pump 300. The control unit 600 may input information based on an operation received from an external device and perform control based on the input information. The control unit 600 may also receive a signal transmitted from another device and perform control based on information indicated by the received signal. The control unit 600 may also perform predetermined processing on the input information or information indicated by the received signal and perform control based on the processing results.

[0017] The TOC meter 500 is a measuring device that measures the total organic carbon concentration of a liquid to be analyzed. The TOC meter 500 performs organic decomposition on the supplied liquid, outputs the electrical conductivity and resistivity values ​​before and after the decomposition as response values, and creates a calibration curve for calculating the total organic carbon concentration from the difference in the response values ​​(output value). The TOC meter 500 decomposes the organic matter in the calibration liquid mixed in the mixing unit 400, measures the electrical conductivity or resistivity of the liquid after the organic matter has been decomposed, and calculates the total organic carbon concentration of the liquid using the above-mentioned calibration curve based on the measured electrical conductivity or resistivity. The TOC meter 500 is a continuous total organic carbon meter that performs measurements periodically. This period may be preset or may be externally configurable. The term "continuous" refers to the fact that once the TOC meter 500 starts operation, it continues measurement unless an instruction to end the operation is input, and the measurement is performed at predetermined intervals. TOC meter 500 is a measuring device with a measurement range of total organic carbon concentration of 0.1 to 500 ppb-C. The calibration curve liquid production system shown in FIG.

[0018] The correction unit 700 corrects the calibration curve created by the TOC meter 500 using the standard addition method from a first output value measured by the TOC meter 500 when the pump 300 is not in operation (or when the control unit 600 has stopped the pump 300 from pumping up the standard solution 210) and a second output value measured by the TOC meter 500 when the control unit 600 is operating the pump 300. Specifically, the correction unit 700 adds the total organic carbon concentration of the ultrapure water obtained using the standard addition method to the total organic carbon concentration of the standard solution 210 pumped up by the pump 300 and diluted with ultrapure water, thereby correcting the calibration curve created by the TOC meter 500. The correction unit 700 may be provided in the TOC meter 500.

[0019] 2 is a diagram illustrating an example of a method by which the correction unit 700 shown in FIG. 1 corrects the calibration curve. In FIG. 2, the x-axis represents the TOC concentration of the standard solution 210 pumped by the pump 300 (0 indicates that the standard solution 210 is not pumped by the pump 300). The y-axis represents the output value of the TOC meter 500. The correction unit 700 uses values ​​output by the TOC meter 500 for a total of two TOC concentrations: one point (first concentration) when the concentration added by the pump 300 is zero and one point (second concentration) when the concentration added by the pump 300 is not zero; preferably, three or more TOC concentrations: one point when the concentration added by the pump 300 is zero and two or more points when the concentration added by the pump 300 is not zero. The graph shown in FIG. 2 plots output values ​​at three points: when the concentration added by the pump 300 is 0 (when the pump 300 is stopped), when the TOC concentration after dilution of the standard solution 210 pumped by the pump 300 is 0.5 ppb-C, and when the TOC concentration is 1.0 ppb-C. The solid line connects the three plotted points. When the concentration added by the pump 300 is 0 (x = 0), TOC is also contained in the ultrapure water from the analysis target liquid line 100, so the measurement value of the TOC meter 500 is not 0 (y = 0). Therefore, the correction unit 700 uses the standard addition method to extend the solid line (represented by a dashed line) and find the intersection with the x-axis. The concentration corresponding to the distance between the coordinate of the intersection with the x-axis and 0 is the TOC concentration of the ultrapure water. The correction unit 700 shifts the calibration curve (the solid and dashed lines) in the positive direction of the x-axis by the amount of the TOC concentration of the ultrapure water. The shifted line is represented by a dashed line, which is the calibration curve after correction.

[0020] FIG. 3 shows an example of output values ​​when a calibration curve is created in a high TOC concentration range. The output values ​​shown in FIG. 3 are electrical conductivity, resistivity, or other values ​​measured by the TOC meter 500 to calculate the TOC concentration, and are used to calculate the TOC concentration. The same applies to FIG. 4, which will be described below. FIG. 3 shows a case where the measurement error of the device is within 1%. As shown in FIG. 3, when the TOC concentration of the standard solution is 500 ppb-C, the theoretical output value is 500, but the actual output value is 502. When the TOC concentration of the standard solution is 1000 ppb-C, the theoretical output value is 1000, but the actual output value is 997. When the TOC concentration of the standard solution is 1500 ppb-C, the theoretical output value is 1500, but the actual output value is 1494. These results are plotted as shown in the lower diagram of Figure 3, and the relationship (calibration curve) between TOC concentration (x) and output value (y) is y = 0.992x + 5.6667. When calculating the output value for a low TOC concentration of 1 ppb-C using this calibration curve, the result is 6.6587, resulting in a large error. Thus, if a calibration curve created using a high-concentration standard solution is used to convert the output value obtained by measuring a low concentration, the resulting measurement value will be unreliable.

[0021] Figure 4 shows an example of output values ​​when a calibration curve is created for a low TOC concentration range. Figure 4 shows a case where the instrument's measurement error is within 1%. As shown in Figure 4, when the TOC concentration of the standard solution is 0.5 ppb-C, the theoretical output value is 0.5, but the actual output value is 0.52. When the TOC concentration of the standard solution is 1.0 ppb-C, the theoretical output value is 1.0, but the actual output value is 0.997. When the TOC concentration of the standard solution is 1.5 ppb-C, the theoretical output value is 1.5, but the actual output value is 1.494. These results are plotted as shown in the lower graph of Figure 4. The relationship between TOC concentration (x) and output value (y) (calibration curve) is y = 0.992x + 0.0057. When the output value at a low TOC concentration of 1 ppb-C is calculated from this calibration curve, it is 0.9977, resulting in a small error. In this way, if the output value obtained from the measurement is converted using a calibration curve created using standard solutions close to the concentration of the target substance, the measurement value obtained by this conversion will be a highly reliable value.

[0022] Thus, calibration curves for measurement instruments used to measure low TOC concentrations must be prepared using low-concentration standard solutions to ensure reliable measurements. However, standard solutions are generally susceptible to environmental contamination between preparation and use. For example, assuming that the increase in TOC concentration due to environmental contamination is 5 ppb-C, preparing a low-concentration standard solution of 5 ppb-C may result in a TOC concentration of 10 ppb-C upon use, depending on the environment. This represents a 100% increase in TOC concentration. On the other hand, preparing a commonly used standard solution of 250 ppb-C may result in a TOC concentration of 255 ppb-C upon use, depending on the environment. This represents a 2% increase in TOC concentration. While preparing and using low-concentration standard solutions is desirable, this is difficult due to the large concentration error. For this reason, standard solutions with commonly used TOC concentrations must be prepared and then diluted to a low concentration before being supplied to the measurement instrument. Therefore, using the present invention, a standard solution with a TOC concentration equivalent to a commonly used TOC concentration is mixed with ultrapure water by adjusting the flow rate of ultrapure water from the line for the liquid to be analyzed and the pumping rate of the standard solution.The mixed liquid is diluted so that the TOC concentration is low, and the diluted solution is supplied inline to the measuring device.Furthermore, to take into account the TOC concentration contained in the ultrapure water to be mixed with the standard solution, the calibration curve is corrected using the TOC concentration of the liquid to be analyzed obtained by the standard addition method.This makes it possible to create a calibration curve with little measurement error when measuring TOC concentrations in the low concentration range (e.g., 1 ppb-C or less).

[0023] Fig. 5 is a diagram showing an example of application of the calibration curve solution production system of the present invention. The example shown in Fig. 5 includes an ultrapure water tank 10, a pump 20, a heat exchanger 30, an ultraviolet oxidation device 31, a non-regenerative ion exchange device 32, a membrane degassing device 33, an ultrafiltration device 34, a flow meter 40, an analysis target liquid line 100, a container 200 storing a standard solution 210, a pump 300, a control unit 600, a mixing coil 410, a TOC meter 500, and a correction unit 700.

[0024] Ultrapure water is supplied from an ultrapure water tank 10 to a heat exchanger 30 using a pump 20, and then sent from the heat exchanger 30 to an analysis target liquid line 100 via an ultraviolet oxidation device 31, a non-regenerative ion exchange device 32, a membrane degassing device 33, and an ultrafiltration device 34. A flow meter 40 is provided in the analysis target liquid line 100. The treatments in the heat exchanger 30, ultraviolet oxidation device 31, the non-regenerative ion exchange device 32, the membrane degassing device 33, and the ultrafiltration device 34, which are each water treatment devices, are the same as those in a general water treatment system.

[0025] Furthermore, the flow meter 40, container 200, standard solution 210, pump 300, control unit 600, TOC meter 500, and correction unit 700 are each the same as those shown in Fig. 1. The mixing coil 410 corresponds to the mixing unit 400 shown in Fig. 1. The mixing coil 410 mixes the standard solution 210 pumped up by the pump 300 with the ultrapure water sent from the analysis target liquid line 100, thereby diluting the standard solution 210.

[0026] Although each component has been described individually above, the components may be combined in any desired configuration, or the functions may be shared among one or more devices. For example, as described above, the correction unit 700 may be provided in the TOC meter 500, or the control unit 600 and correction unit 700 may be provided in the TOC meter 500. Alternatively, the control unit 600 and correction unit 700 may be provided in a device separate from the TOC meter 500, and the device may communicate with the TOC meter 500 to exchange signals. Furthermore, the present system may also include a general ultrapure water production device or water treatment device (e.g., an ultrafiltration device). [Explanation of symbols]

[0027] 10 Ultrapure water tank 20,300 pumps 30 heat exchanger 31 Ultraviolet oxidation device 32 Non-regenerative ion exchange device 33 Membrane degassing device 34 Ultrafiltration device 40 Flow meter 100 Analysis target liquid line 110 Standard solution line 200 containers 210 standard solution 400 Mixing section 410 Mixed Coil 500 TOC meter 600 control section 700 Correction Unit

Claims

1. A calibration curve liquid producing system that produces and supplies a calibration curve liquid for producing a calibration curve to a measuring device that measures the total organic carbon concentration of a liquid to be analyzed using the calibration curve, a first liquid delivery line for delivering a dilution liquid to the measurement device; a second liquid transfer line for transferring a standard solution to the first liquid transfer line; a mixing unit provided in the first liquid sending line, which mixes the dilution liquid and the standard solution to dilute the standard solution; a pump provided in the second liquid supply line to supply the standard solution to the first liquid supply line; a control unit for controlling the supply amount of the pump; a correction unit that corrects the calibration curve created by the measurement device based on the total organic carbon concentration of the diluted solution obtained using a standard addition method from a first concentration measured by the measurement device while the control unit stops the pump and sends the diluted solution to the measurement device, and a second concentration measured by the measurement device while the control unit operates the pump and sends the calibration curve solution to the measurement device, the correction unit extends, using the standard addition method, a straight line connecting the point X=0 at which the control unit stops the pump and an arbitrary point of total organic carbon concentration after the control unit operates the pump and dilution of the standard solution supplied to the first liquid supply line, on an XY coordinate plane, where the X coordinate is the total organic carbon concentration of the standard solution supplied by the pump to the first liquid supply line, and the Y coordinate is the total organic carbon concentration measured by the measurement device; and corrects the calibration curve by moving the straight line in the positive direction of the X axis by the distance from the intersection of the extended straight line and the X axis of the XY coordinate plane to the origin; a calibration curve liquid producing system that supplies the mixture of the dilution liquid and the standard solution mixed in the mixing section to the measuring device as the calibration curve liquid;

2. 2. The calibration curve solution producing system according to claim 1, The control unit controls the pump based on the liquid feed rate of the diluted liquid in the first liquid feed line and the total organic carbon concentration of the standard liquid so that the total organic carbon concentration of the calibration curve liquid is below a predetermined value.

3. 3. The calibration curve solution producing system according to claim 2, The predetermined value is 100 ppb-C.

4. 4. The calibration curve solution producing system according to claim 2, wherein: The control unit controls the pump so that the standard solution is supplied to the first liquid supply line at a liquid supply speed that is 1 / 100 or less of the liquid supply speed of the dilution solution in the first liquid supply line.

5. 4. The calibration curve solution producing system according to claim 1, A calibration curve liquid manufacturing system for manufacturing a calibration curve liquid for creating a calibration curve for the measuring device that decomposes organic matter in the liquid mixed by the mixing unit, measures the electrical conductivity or resistivity of the liquid into which the organic matter has been decomposed, and calculates the total organic carbon concentration of the liquid based on the measured electrical conductivity or resistivity.

6. 4. The calibration curve solution producing system according to claim 1, The measuring device is a calibration solution producing system having a measurement range of total organic carbon concentration of 0.1 to 500 ppb-C.

7. The calibration curve solution producing system according to any one of claims 1 to 3, a measurement system comprising the measurement device;

8. 1. A method for producing a calibration curve liquid, the method comprising: producing and supplying a calibration curve liquid for preparing a calibration curve to a measuring device that measures the total organic carbon concentration of a liquid to be analyzed using the calibration curve; diluting the standard solution by mixing the dilution solution sent to the first liquid sending line to the measurement device with the standard solution sent to the first liquid sending line from a second liquid sending line for sending a standard solution; a pump provided in the second liquid supply line to supply the standard solution to the first liquid supply line; a control unit for controlling the supply amount of the pump; correcting the calibration curve created by the measuring device based on the total organic carbon concentration of the diluted solution obtained using a standard addition method from a first concentration measured by the measuring device while the diluted solution is being fed to the measuring device by stopping a pump provided in the second liquid feed line and supplying the standard solution to the first liquid feed line, and a second concentration measured by the measuring device while the pump is operating and feeding the calibration curve solution to the measuring device; In the correction, on an XY coordinate plane, where the total organic carbon concentration of the standard solution supplied by the pump to the first liquid supply line is the X coordinate and the total organic carbon concentration measured by the measurement device is the Y coordinate, a straight line connecting the point X=0 at which the control unit stops the pump and an arbitrary point of total organic carbon concentration after the control unit operates the pump and dilutes the standard solution supplied to the first liquid supply line is extended using the standard addition method, and the straight line is moved in the positive direction of the X axis by the distance from the intersection of the extended straight line and the X axis of the XY coordinate plane to the origin, thereby correcting the calibration curve; a mixed solution of the diluted solution and the standard solution, the mixed solution being supplied to the measuring device as the calibration solution;

Images