JP2019095411A - Flow injection analysis method and device - Google Patents

Abstract

To provide a flow injection analysis device with which it is possible to continuously and automatically perform quantitation over a long period and also automatically perform the operation of re-drawing a calibration curve.SOLUTION: The present invention is provided with an introduction device for selecting a sample liquid and a standard liquid, a sampling valve for injecting a fixed amount of the liquid selected by the introduction device into a carrier liquid that is supplied to a reaction coil, and a detector for outputting a detection value and connected to the secondary side of the reaction coil. Furthermore, a control unit is included that executes the continuous quantitation of a target substance in the sample liquid, controls the introduction device and the sampling valve so as to switch between the sample liquid and the standard liquid in a period in which the continuous quantitation is performed, recalculates a calibration curve on the basis of a detection value for the standard liquid, fits a detection value for the sample liquid to the recalculated calibration curve after the recalculation, and calculates the quantitative value of the target substance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flow injection analysis (FIA) method and apparatus.

  A continuous stream of liquid is formed in a thin tube, into which a sample solution is injected to cause a reaction with a reagent, and the concentration of reaction products etc. is measured by a detector connected to the secondary side of the tube Flow injection analysis is widely used for quantitative analysis of a target substance in a sample solution. The thin tube where the reaction takes place is generally referred to as the reaction coil. For quantification by flow injection analysis, prepare a standard solution in which the concentration of the target substance is known separately from the sample solution, determine a calibration curve based on the quantification result for the standard solution, and apply the detection result for the sample solution to the calibration curve Generally, it is desirable to quantify the target substance contained in the sample solution. The calibration curve can be said to be a function indicating the relationship between the detection result of the detector and the amount (or concentration) of the target substance in the sample solution. If only this function becomes clear, it is possible to quantify the target substance from the detection value of the detector without actually drawing a calibration curve as a graph. In the following description, obtaining a function indicating the relationship between the detection result of the detector and the amount (or concentration) of the target substance in the sample solution, obtaining a calibration curve, drawing a calibration curve, or obtaining a calibration curve Call it calculated.

  As an application example of flow injection analysis, for example, Patent Document 1 discloses carrying out colorimetric analysis with diacetyl monoxime by flow injection analysis to continuously monitor a trace amount of urea concentration in sample water. ing. The determination by colorimetric method using diacetyl monoxime is well known as a method of determining urea, and is described, for example, in the Sanitary Test Method (Non-patent Document 1). In the colorimetric method using diacetyl monoxime, other reagents (for example, antipyrine + sulfuric acid solution, aqueous solution of semicarbazide hydrochloride, aqueous solution of manganese chloride + potassium nitrate, sodium dihydrogen phosphate + sulfuric acid solution, etc.) for the purpose of accelerating the reaction. Can be used together. When antipyrine is used in combination, diacetyl monooxime is dissolved in an acetic acid solution to prepare a diacetyl monoximetic acetic acid solution, and antipyrine (1,5-dimethyl-2-phenyl-3-pyrazolone) is dissolved in, for example, sulfuric acid. An antipyrine-containing reagent solution is prepared, a diacetyl monoximetic acetic acid solution and an anpyriline-containing reagent solution are sequentially mixed with sample water, absorbance at a wavelength of about 460 nm is measured, and quantification is performed using a control with a standard solution. The method of quantitative determination of urea by the colorimetric method using diacetyl monoxime is originally intended for the determination of urea in, for example, pool water or public bath water, but this method is described in Patent Document 1 As a result, by applying flow injection analysis to measure the absorbance, urea can be quantified on-line continuously in a concentration range of less than ppb to several ppm.

JP, 2000-338099, A

Japan Pharmaceutical Association, Hygienic Test Act, Commentary 1990.4.1.2.3 (13) 1 (1990 Edition 4th Printing Supplement (1995), p1028), 1995

  In the case of continuously quantifying the target substance on-line continuously for a long time using flow injection analysis, it is preferable to perform automatic measurement over the entire measurement period. In addition, during a long measurement period, denaturation of the reagent or change in detection characteristics of the detector may occur. Therefore, it is necessary to measure the standard solution at certain intervals and redraw the calibration curve. However, in flow injection analysis, it is necessary for a person to judge the reworking of the calibration curve, and even when performing automation and continuous quantification, the operation itself for reworking the calibration curve had to be performed manually. .

  An object of the present invention is to provide a flow injection analysis method and apparatus capable of performing quantification continuously and automatically over a long period of time, and also capable of automatically performing an operation of redrawing a calibration curve.

  The flow injection analysis method of the present invention is a flow injection analysis method in which a continuous liquid flow is formed in a reaction coil, and the target substance in a sample liquid is quantified based on the reaction with a reagent in the reaction coil. Within the period of continuous quantification, the sample solution is automatically switched to the standard solution and introduced into the reaction coil, and the calibration curve is recalculated based on the detection value for the standard solution, and the calibration curve is recalculated. The method is characterized in that the detection value for the sample solution is applied to the recalculated calibration curve to automatically calculate the quantitative value of the target substance.

  The flow injection analysis device of the present invention is a flow injection analysis device that forms a continuous flow of liquid in a reaction coil and quantifies a target substance in a sample liquid based on a reaction with a reagent in the reaction coil, An introduction device for selecting a solution and a standard solution, a sampling valve for injecting a fixed amount of the solution selected by the introduction device into the carrier liquid supplied to the reaction coil, and detection circuit connected to the secondary side of the reaction coil The detector that outputs the value and the continuous quantification of the target substance in the sample solution are executed, and the sample solution is switched to the standard solution for recalculation of the calibration curve within the period of continuous quantification. Control the introduction device and the sampling valve so as to introduce them into the reaction coil, recalculate the calibration curve based on the detection value for the standard solution, and after recalculation, use the recalculated calibration curve Applying the detected value for the sample liquid and has a control means for calculating a quantitative value of the target substance, the.

  According to the present invention, in various types of analysis represented by flow injection analysis, quantification can be continuously and automatically performed over a long period of time, and an operation to redraw a calibration curve can also be automatically performed. Become.

It is a figure which shows the structure of the flow-injection analyzer of one Embodiment of this invention. It is a graph which shows the change of the peak intensity and urea concentration in a detector with respect to the water flow days. It is a graph which shows the relationship of the water flow days in Example 2, and peak intensity.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a flow injection analysis (FIA) apparatus according to an embodiment of the present invention. Here, raw water used for pure water production or pure water is used as a sample solution, and a trace amount of urea contained in this sample solution (which can be referred to as sample water here) can be continuously quantified online as a target substance. Taking the case as an example, the present invention will be described, which can automate and carry out continuous quantitative measurement over a long period of time, and can also carry out the process of retracement of the calibration curve automatically during this measurement period. Of course, the target substance to be quantified in the present invention is not limited to urea, and the sample liquid containing the target substance is not limited to water. For example, the FIA device of the present embodiment can be connected to some kind of water treatment system (a pure water production device can also be said to be a kind of water treatment system), and can measure water from the water treatment system.

  As shown in FIG. 1, a line 20 of raw water used for pure water production is provided. In this line 20, raw water is supplied by a pump P0. A pipe 21 branched from the raw water line 20 is provided. The pipe 21 supplies sample water branched from the raw water to the introduction device 60, and an open / close valve 22 and a flow meter FI are provided in the middle of the section up to the introduction device 60. When analyzing the urea concentration in the sample water collected from the raw water, the on-off valve 22 is always open.

  The introduction device 60 selects and supplies, to the main portion of the FIA device, one of the sample water branched from the raw water and a standard solution containing a known amount of the target substance (in the example shown here, urea). . The introduction device 60 includes a sample water tank 61 for temporarily storing sample water branched from raw water, two containers 62 and 63 for storing standard solutions of different concentrations, and either the sample water tank 61 or the containers 62 and 63 for standard solutions. A selection valve 64 is provided to select one or the other. The sample water tank 61 is of the so-called flow cell type, and a pipe 22 of sample water branched from the raw water is connected to the bottom thereof. The upper surface of the sample water tank 61 is closed by a ferrule through which a pipe 65 connected to the selection valve 64 passes. The pipe 65 vertically extends from the upper surface side of the sample water tank 61 to a substantially central region, and its tip is open. Furthermore, a pipe 68 is connected to the upper portion of the sample water tank 61 in order to drain sample water which becomes overflow. As long as the pump P0 is driven, sample water always flows into the sample water tank 61 via the pipe 21. It can be said that the sample water tank 61 is a container through which the sample liquid flows continuously so as to overflow. The containers 62 and 63 of the standard solution are connected to the selection valve 64 by pipes 66 and 67, respectively.

  The selection valve 64 may be any one of the sample water supplied by the pipe 65, the standard solution in the container 62 supplied via the pipe 66, and the standard solution in the container 63 supplied via the pipe 67. The selected liquid is selectively supplied to the sampling valve 10 provided in the body portion of the FIA device through a pipe 70 connected to the selective valve 64. As described later, the pump P4 is connected to the sampling valve 10. However, by driving the pump P4, the liquid selected by the selection valve 64 is constantly supplied to the sampling valve 10. In the example described here, two standard solutions having different concentrations of the target substance (here, urea) are prepared, but the number of standard solutions is not limited to two. When expressing a calibration curve with a curve such as a quadratic curve, prepare three or more standard solutions of different concentrations. Although it is possible to use only a single standard solution, from the viewpoint of quantitative accuracy, it is preferable to use at least two or more standard solutions having different concentrations.

  In the introduction apparatus 60 of the present embodiment, the sample water tank 61 is configured to be able to overflow, so the sample water flows from the sample water tank 61 toward the selection valve 64 because the selection valve 64 selects the standard solution. Even when not, the flow of sample water to and within the sample reservoir 61 is not interrupted. The sample water tank 61 has a closed structure except for the connection with the pipes 21, 65 and 68, and the test water flowing from the pipe 21 into the sample water tank 61 flows upward, and the selection valve 64 is connected via the pipe 65. The sample water other than the amount that has flowed out flows out of the sample water tank 61 through the pipe 68. By using such a sample water tank 61, even when the concentration of the target substance in the sample water changes, sampling of the sample water can be appropriately performed in a form that follows the change. The introducing device 60 is preferably used when selecting and introducing one of the sample solution and the standard solution to not only the FIA device but also other types of analyzers.

  Next, the sampling valve 10 will be described. The portion downstream of the sampling valve 10 including the sampling valve 10 is a main body portion having a configuration as an FIA device, and is a portion actually involved in the determination of urea. The sampling valve 10 is supplied with a sample water or standard solution selected by the introduction device 60 from the introduction device 60. For simplification of the description, when the sample water is referred to in the following description of the sampling valve 10, the case of being a standard solution is also included.

  The sampling valve 10 has a configuration generally used in the FIA method, and includes a six-way valve 11 and a sample loop 12. The six-way valve 11 has six ports indicated by circled numbers in the figure. The pipe 70 from the introduction device 60 is connected to the port 2. Further, a pipe 23 to which carrier water is supplied via the pump P1 is connected to the port 6, and a pipe 25 for draining the sample water is connected to the port 3 via the pump P4. Between port 1 and port 4, a sample loop 12 for collecting a predetermined volume of sample water is connected. One end of a pipe 24 serving as an outlet of the sampling valve 11 is connected to the port 5. Carrier water is water substantially free of urea, and is, for example, pure water.

  Assuming that the communication between the port X and the port Y in the six-way valve 11 is represented by (X-Y), the six-way valve 11 is (1-2), (3-4), (5-6) The first state and the second state of (2-3), (4-5), and (6-1) can be switched. In FIG. 1, the connection between ports in the first state is shown by a solid line, and the connection between ports in the second state is shown by a dotted line. In the first state, the carrier water flows from piping 23 → port 6 → port 5 → piping 24 and flows out from sampling valve 10 to the downstream side. The sample water flows from the pipe 70 → port 2 → port 1 → sample loop 12 → port 4 → port 3 and is discharged from the pipe 25. When switching from the first state to the second state, the sample water flows from the piping 70 → port 2 → port 3 and is discharged from the piping 25, and the carrier water is from piping 23 → port 6 → port 1 → Sample loop 12 → port 4 → port 5 → pipe 24 flows and flows downstream. At this time, the sample water which has already flowed into the sample loop 12 when in the first state and fills the inside of the sample loop 12 flows from the port 5 into the pipe 24 before the carrier water, to the downstream side of the sampling valve 10 Flow. The volume of sample water flowing into the pipe 24 is defined by the sample loop 12. Therefore, by repeatedly switching the first state and the second state (for example, by rotating the six-way valve 11 in the direction of the arrow), a predetermined volume of sample water can be repeatedly fed into the pipe 24. The switching between the first state and the second state can be performed at predetermined time intervals in consideration of a residence time necessary for a reaction described later and a time until the detector 32 detects urea. Moreover, it can also be detected by detecting that the sample water introduced into the detector 32 has been discharged from the detector 32. As described above, by automatically switching between the first state and the second state, urea can be quantified continuously.

  In this apparatus, the FIA method is applied to the determination of urea by colorimetric method using diacetyl monoxime. Therefore, a diacetyl monoximetic acid solution (hereinafter also referred to as reagent A) and an antipyrine-containing reagent solution (hereinafter also referred to as reagent B) are used as reaction reagents used for the determination of urea. Although the case where an antipyrine containing reagent solution is used as a reagent used together with diacetyl monoxime is described here, the reagent used together with diacetyl monoxime is not limited to the antipyrine containing reagent solution. Reagent A and reagent B are stored in storage tanks 41 and 42, respectively.

  After preparation of these reagents, the peak intensity in absorbance measurement decreases when kept at room temperature for a long period (for example, several days or more) for continuous determination of urea, and this peak It has been found that a reduction in strength can be prevented by refrigeration of the reagent (especially reagent B). Since it is preferable that the peak intensity in absorbance measurement does not decrease in order to perform stable determination, the storage tanks 41 and 42 are provided in the refrigeration unit 40 in the FIA device of the present embodiment. The reagent A is prepared by dissolving diacetyl monoxime in an acetic acid solution. However, when the refrigeration unit 40 is provided, the preparation itself is performed in the storage tank 41, or the reagent A is stored in the storage tank 41 after its preparation. Do. Similarly, the reagent B is prepared by dissolving antipyrine in, for example, sulfuric acid, but the preparation itself is performed in the reservoir 42, or the reagent B is stored in the reservoir 42 after its preparation. The refrigeration unit 40 shields the storage tanks 41 and 42 from light and cools the storage tanks 41 and 42, whereby the temperatures of the reagents A and B in the storage tanks 41 and 42 are 20 ° C. or less, preferably 3 ° C. to 20 ° C. The temperature is maintained at 5 ° C. or more and 15 ° C. or less, more preferably. The storage tank 41 for storing the reagent A may not necessarily be disposed in the refrigeration unit 40 as long as it can be stored in a light-shielded state. Even if the refrigeration temperature of the reagent is less than 5 ° C., it is acceptable if precipitation of crystals does not occur in the reagent. According to the hygiene test method (Non-patent document 1), antipyrine sulfate solution in which antipyrine is dissolved in sulfuric acid can be used for 2 to 3 months if it is stored in a brown bottle, and crystals are precipitated and re-dissolve even if returned to room temperature. Although it is described that refrigerated storage is not suitable because it does not, the present inventors confirmed by experiments that the antipyrine sulfuric acid solution prepared according to the hygienic test method does not crystallize even at 3 ° C.

  One end of a pipe 26 is connected to the storage tank 41, and the other end of the pipe 26 is connected to the pipe 24 by a mixing unit 43. The pipe 26 is provided with a pump P2 for feeding the reagent A into the pipe 24 at a predetermined flow rate. Similarly, one end of a pipe 27 is connected to the storage tank 42, and the other end of the pipe 27 is connected to the pipe 24 by a mixing unit 44. The pipe 27 is provided with a pump P3 for feeding the reagent B into the pipe 24 at a predetermined flow rate. The mixing units 43 and 44 each have a function of uniformly mixing the reagent A and the reagent B with the flow of liquid in the pipe 24. The other end of the pipe 24 is connected to the inlet of the reaction coil 31 provided in the reaction constant temperature chamber 30. The reaction coil 31 causes a coloring reaction between urea and diacetylmonoxime in the presence of antipyrine, and the length and the flow rate inside the reaction coil 31 indicate the residence time required for the reaction. It is selected appropriately according to The reaction thermostat 30 heats the reaction coil 31 to a temperature suitable for the reaction, and for example, heats the reaction coil 31 to a temperature of 50 ° C. to 150 ° C., preferably 90 ° C. to 120 ° C. .

  At the end of the reaction coil 31, that is, at the outlet, a detector 32 is provided for measuring the absorbance of the color generated in the liquid by the color reaction for the liquid flowing out of the reaction coil 31. The detector 32 measures, for example, the absorbance at around a wavelength of 460 nm and outputs it as a detection result. At the outlet of the detector 32, a back pressure coil 33 is provided which applies a back pressure to a line from the pump P1 to the detector 32 through the sampling valve 10, the pipe 24 and the reaction coil 31. A pressure gauge PI is connected to a position between the outlet of the detector 32 and the inlet of the back pressure coil 33. The drainage of this FIA device flows out from the outlet of the back pressure coil 33.

  In the FIA device of the present embodiment, the six-way valve 11 is driven to switch between the first state and the second state as described above, and the sample water or any standard solution is selected by the selection valve 64. A control unit 50 is further provided to select the. The control unit 50 receives the detection result of the detector 32. The control unit 50 corresponds to a control means, and controls the introduction device 60 (in particular, the selection valve 64) and the sampling valve 10 (in particular, the six-way valve 11), and detects the standard liquid selected by the selection valve 64 A calibration curve is calculated on the basis, and when sample water is selected, a detection result for the sample water is applied to the calculated calibration curve to determine a urea concentration in the sample water and perform processing for outputting as a quantitative result. When calculating the calibration curve or determining the urea concentration, the control unit 50 calculates a peak value (ie, peak intensity) in the detection result input from the detector 32, or a peak area obtained by integrating the detection result with respect to time. Calculate and use. At that time, the absorbance when carrier water is flowing is used as a baseline, and the peak intensity or peak area with respect to this baseline is determined.

  Next, calculation of a calibration curve when urea is continuously quantified will be described. By measuring the urea concentration at a predetermined time interval t using the FIA apparatus of the present embodiment, it is assumed that the urea concentration in the sample water is continuously measured over a long period of time. At this time, the control unit 50 first controls the selection valve 64 so that the standard solutions in the containers 62 and 63 are sequentially supplied to the sampling valve 10, and further controls the sampling valve 10 to perform these standards. Perform measurements on the fluid. Then, based on the detection result obtained by the detector 32 for each standard solution, the control unit 50 calculates a calibration curve. Subsequently, the control unit 50 controls the selection valve 64 so that the sample water is supplied to the sampling valve 10, and controls the sampling valve 10 so that the sample water is introduced to the pipe 24 at every time interval t. Do. The control unit 50 determines the urea concentration in the sample water by applying the result obtained from the detector 38 for the sample water to the previously generated calibration curve, and outputs the result as a quantitative result. As a result, the urea concentration is determined at each time interval t.

  When the measurement period in which continuous quantification is performed is a long period and there is a concern that the denaturation of each reagent or the fluctuation of the detection characteristic of the detector 32 may occur during that period, the control unit 50 At every calculation interval T (where T t t), processing for redrawing the calibration curve, that is, processing for recalculating the calibration curve is performed. In the process of recalculating the calibration curve, the control unit 50 controls the selection valve 64 to select the standard solution at a timing that does not affect the measurement of the sample water, and controls the sampling valve 10 in that state to measure the standard solution. Are introduced into the pipe 24. Then, based on the detection result from the detector 32 at that time, the calibration curve is recalculated. After recalculation of the standard curve, the urea concentration in the sample water is determined based on the recalculated standard curve. In the present embodiment, the calibration curve is calculated using two types of standard solutions, but if it is not possible to secure the time for performing measurement for both standard solutions during the measurement interval t of the sample water, The standard solution may be measured, and then the sample water may be measured once, and then the other standard solution may be measured to recalculate the calibration curve. In order to suppress consumption of the standard solution, it is preferable that the selection valve 64 select the sample solution in a period other than the period necessary for performing measurement on the standard solution. It is preferable that the calibration curve calculation interval T can be arbitrarily set according to the reagent to be used and the configuration of the FIA apparatus. In addition, it is preferable that the calibration curve calculation interval T can be appropriately changed even in the middle of a long measurement period. For example, under conditions where the measurement ambient temperature is different, the reduction rate of peak intensity in absorbance measurement is different. The calibration curve calculation interval T is set at equal intervals immediately after the start of measurement, and if the reduction ratio of the peak intensity of the standard solution calculated before and after the calibration curve calculation interval T exceeds a certain range, the calibration curve calculation interval T can be shortened automatically. In addition, when the reduction ratio of the peak intensity of the standard solution calculated before and after the calibration curve calculation interval T falls within a certain range, the calibration curve calculation interval T can be automatically extended. By extending the calibration curve calculation interval T, it becomes possible to reduce the amount of standard solution used. The calibration curve calculation interval T differs depending on the composition and properties of the sample water.

  In the apparatus of the present embodiment, the urea in the sample water can be measured online continuously over a long period of time by the colorimetric method using diacetyl monoxime, utilizing the FIA method, and moreover, during that period, Since the calibration curve is automatically recalculated even if a change occurs, urea can be quantified stably and accurately over a long period of time. Also, by using, as reagent A (diacetyl monoximetic acid solution) and reagent B (antipyrin-containing reagent solution) used for the reaction, particularly those of reagent B, those kept at 20 ° C. or lower after preparation of those reagents. It becomes possible to carry out continuous determination of urea more stably over a long period of time.

  The invention will now be described in more detail by way of examples.

Example 1
The FIA apparatus shown in FIG. 1 was assembled. In the containers 62 and 63, standard solutions each having a urea concentration of 3 ppb and 10 ppb were stored. A diacetyl monoximetic acid solution is prepared as reagent A, an antipyrin-containing reagent solution is prepared as reagent B, these reagents are immediately stored in storage tanks 41 and 42, and each reagent is directed to piping 24 from storage tanks 41 and 42. It was made to supply continuously. In this example, the refrigeration unit 40 was not used, and the reagent A and the reagent B were maintained at room temperature. As sample water, a solution in which urea was dissolved in pure water so that the urea concentration was 5 ppb was used. Then, the sample water is measured once every 30 minutes, and the calibration curve is recalculated once every 60 minutes to continuously measure the urea concentration of the sample water for about 10 days. went. The change of the obtained urea concentration is shown in FIG. At this time, assuming that the peak intensity of absorbance when measuring the sample water immediately after preparing the reagent A and the reagent B is 100%, the change in the peak intensity of absorbance when performing continuous measurement of the sample water Examined. The change in peak intensity is also shown in FIG.

  As shown in FIG. 2, since the denaturation of the reagent proceeds by maintaining the reagent at normal temperature, the peak intensity decreases as the number of days from the preparation time passes, but by repeating the recalculation of the calibration curve It has been found that it is possible to measure the urea concentration (5 ppb in this case) in the sample water stably and accurately.

(Example 2)
Next, the FIA apparatus shown in FIG. 1 was assembled to demonstrate the effect of refrigerated reagents. However, the portion from the piping 20 to the introduction device 60 was not provided, and the sample water was directly supplied to the sampling valve.

  The standard solution prepared to have a urea concentration of 60 ppb was continuously supplied to the sampling valve 10 as sample water. Then, continuous monitoring of the urea concentration was performed on this urea standard solution. Here, it was examined how the urea concentration obtained as the measurement value of the detection peak of the absorbance in the detector 32 changes when the measurement is continuously performed on the urea standard solution. In this example 2, 2 g of diacetyl monoxime is dissolved in 100 mL of 10% acetic acid to prepare reagent A (diacetyl monoximetic acid solution), 0.2 g of antipyrine is taken, it is dissolved in 9 mol / L sulfuric acid, and the total amount is 100 mL. As a reagent B (antipyrin-containing reagent solution) was prepared, and immediately after preparation, the reagents were stored in the storage tanks 41 and 42, respectively, and each reagent was continuously supplied from the storage tanks 41 and 42 to the pipe 24. After each reagent was injected into the reservoirs 41 and 42 at the beginning of the continuous measurement, the reagent was not replenished during the continuous measurement. In addition, the storage tank 41 of the reagent A was maintained at normal temperature. With respect to the reagent B, experiments were conducted in two ways, one at a storage temperature of 10 ° C. and one at a storage temperature of 25 ° C. The change in urea concentration was confirmed by the peak intensity of absorbance at a wavelength of 460 nm. The results are shown in FIG. In FIG. 3, measurement was made when the same urea standard solution was measured with the peak intensity at 100% when the 60 ppb urea standard solution was measured immediately after preparing reagent A and reagent B and storing them in storage tanks 41 and 42, respectively. It shows how the value changed as the date and time passed.

  As shown in FIG. 3, when the antipyrine-containing reagent solution (reagent B) is maintained at 25 ° C., the peak intensity gradually decreases, and the peak intensity is 72% during 10 days of operation for continuous measurement. Down to. That is, it has been impossible to stably determine the amount of urea. On the other hand, when the antipyrine-containing reagent solution is stored under refrigeration and maintained at 10 ° C, it is found that the peak intensity does not decrease even after 10 days of continuous operation, and continuous determination of urea can be stably performed over a long period of time The

(Example 3)
After preparing reagent B (antipyrin-containing reagent solution) in the same manner as in Example 2, each was stored at 5 ° C., 10 ° C., 15 ° C., 20 ° C., and 25 ° C. for 10 days. Then, after this storage, the reagent B was supplied to the apparatus of Example 2. Immediately after the reagent B was supplied to the apparatus, a standard solution with a urea concentration of 60 ppb was measured using this apparatus to determine its peak intensity. At that time, the peak intensity was 100% when the standard solution was measured immediately after preparation of the reagent B. The reagent A (diacetyl monoximetic acid solution) was prepared in the same manner as in Example 2 and then stored at room temperature. The results are shown in Table 1.

  As shown in Table 1, when the storage temperature is 5 ° C. and 10 ° C., almost no drop in peak intensity is observed, and when stored at 15 ° C., the peak intensity drops by about 10%. It was observed. When stored at 20 ° C., the peak intensity decreased by about 20%, but at 25 ° C., the peak intensity decreased by nearly 30%. From these, in order to continuously measure a trace amount of urea concentration, at least the antipyrin-containing reagent solution among the reagents (diacetyl monoximetic acetic acid solution and the antipyrin-containing reagent solution) used for the reaction should be stored under refrigeration. In the case, it was found that the temperature of the antipyrin-containing reagent solution is preferably maintained at 20 ° C. or less, more preferably 3 ° C. or more and 20 ° C. or less, and still more preferably 5 ° C. or more and 15 ° C. or less .

(Example 4)
The same test as in Example 3 was conducted, except that the reagent A (diacetyl monoximetic acid solution) in Example 3 was stored at the same storage temperature as the reagent B (antipyrin-containing reagent solution) in Example 3. .

  When both reagent A and reagent B were refrigerated and measurement was performed, only reagent B was refrigerated and measurement was performed (Table 1).

DESCRIPTION OF SYMBOLS 10 Sampling valve 12 Sample loop 31 Reaction coil 32 Detector 40 Refrigeration part 41, 42 Storage tank 50 Control part 60 Introduction apparatus 61 Sample water tank 62, 63 Container 64 Selection valve

Claims (11)

In a flow injection analysis method of forming a continuous flow of liquid in a reaction coil and quantifying a target substance in a sample liquid based on a reaction with a reagent in the reaction coil,
The sample solution is automatically switched to the standard solution and introduced into the reaction coil within a period during which the target substance is continuously quantified, and the calibration curve is recalculated based on the detection value for the standard solution. ,
After recalculation of the calibration curve, a detection value for the sample solution is applied to the recalculated calibration curve, and a quantitative value of the target substance is automatically calculated. .   The flow injection analysis method according to claim 1, wherein the calibration curve is periodically recalculated.   The flow injection analysis method according to claim 1 or 2, wherein the sample liquid is water obtained by on-line connection from a water treatment system.   The flow injection analysis method according to any one of claims 1 to 3, wherein the target substance is urea.   The flow injection analysis method according to any one of claims 1 to 4, wherein after preparing the reagent, at least one of the reagents is refrigerated. A flow injection analyzer which forms a continuous flow of liquid in a reaction coil and quantifies a target substance in a sample liquid based on a reaction with a reagent in the reaction coil,
An introduction device for selecting a sample solution and a standard solution;
A sampling valve for injecting a fixed amount of the liquid selected by the introduction device into the carrier liquid supplied to the reaction coil;
A detector connected to the secondary side of the reaction coil to output a detected value;
Continuous quantitative determination of the target substance in the sample solution is performed, and the sample solution is switched to the standard solution for recalculation of a calibration curve within a period in which the continuous quantitative determination is performed, and the reaction is performed. The introduction device and the sampling valve are controlled to be introduced into the coil, the calibration curve is recalculated based on the detected value for the standard solution, and the recalculation is performed after the recalculation is performed. Control means for calculating a quantitative value of the target substance by applying a detection value to the sample liquid to the
Flow injection analyzer. The introduction device is
Two or more containers for storing standard solutions of different concentrations,
A container through which the sample solution flows;
In order to supply any one of the standard solution and the sample solution to the analyzer, one of two or more containers of the standard solution and a container of the sample solution is selected and selected. A selection valve for delivering liquid towards the sampling valve;
The flow injection analyzer according to claim 6, which has   The flow injection analyzer according to claim 6, wherein the control means periodically recalculates the calibration curve.   The flow injection analyzer according to any one of claims 6 to 8, connected online to a water treatment system, wherein the target substance is quantified using water obtained from the water treatment system as the sample liquid.   The flow injection analyzer according to any one of claims 6 to 9, wherein the target substance is urea. A reservoir for storing at least one of said prepared reagents;
Cooling means for cooling the storage tank;
The flow injection analyzer according to any one of claims 6 to 10, comprising:

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