JP2019095410A - Flow injection analysis method and device - Google Patents

Abstract

To reduce a reagent amount consumed when continuously quantitating a target substance in flow injection analysis.SOLUTION: In a flow injection analysis method for forming a continuous flow of liquid in a reaction coil and continuously quantitating a target substance in a sample liquid on the basis of reaction with a reagent in the reaction coil, the introduction of the sample liquid into the reaction coil where a carrier liquid flows is repeated and the quantitation of the target substance is thereby repeatedly executed, and reagent supply to the reaction coil is discontinued in correspondence to a period in which the quantitation of the target substance by repeated execution is not performed.SELECTED DRAWING: Figure 1

Description

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

  Flow injection analysis is performed by forming a continuous stream of liquid in a thin tube, injecting a sample solution into it to cause a reaction with a reagent, and measuring the reaction product concentration etc. on the secondary side of the tube. It is widely used for quantitative analysis of target substances in liquid. The thin tube where the reaction takes place is generally referred to as the reaction coil. In a general flow injection apparatus, a sample solution is injected into the carrier solution so that a part of the continuous carrier solution flow is replaced with the sample solution, and a reagent solution prepared separately from this is continuously used as the carrier solution. The mixture is introduced into the reaction coil, and the reagent and the target substance are reacted in the reaction coil. For example, Patent Document 1 discloses that flow analysis is performed by colorimetric analysis with diacetyl monoxime to continuously monitor a trace amount of urea concentration in sample water.

  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 absorbance, urea can be quantified continuously in the concentration range of ppb or less 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

  Consider the case of continuously quantifying a target substance online using flow injection analysis. In this case, the target substance in the sample solution is quantified at fixed time intervals. The characteristic of the flow injection method is that the amount of reagent can be small, but when measuring continuously over a long period, for example, several weeks or several months, the amount of reagent consumed throughout the entire period is It will be huge. There is a need to reduce the amount of reagents consumed when performing quantification continuously by flow injection analysis. Even if the flow rate of the reagent solution is 0.5 mL / min, the reagent solution consumed per day is 720 mL, and if it is one month, it will exceed 20 L.

  An object of the present invention is to provide a flow injection analysis method and apparatus capable of reducing the amount of reagents consumed when continuously quantifying a target substance.

  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 target substances in a sample solution are continuously quantified based on the reaction with a reagent in the reaction coil. The target substance is repeatedly quantified by repeatedly introducing the sample solution into the reaction coil through which the carrier liquid flows, and the reagent is supplied to the reaction coil in a period in which the target substance in the repetitive execution is not quantified. To suspend.

  The flow injection analysis apparatus of the present invention is a flow injection analysis apparatus that continuously forms a continuous flow of liquid in a reaction coil and continuously determines a target substance in a sample liquid based on a reaction with a reagent in the reaction coil. And adding a reagent to the carrier liquid into which the sample liquid has been injected at a position between the sampling valve and the reaction coil, and a sampling valve that injects a fixed amount of sample liquid to the carrier liquid flowing toward the reaction coil Controlling the sampling valve to repeat the injection of the sample solution into the carrier water, and adding the addition means to interrupt the addition of the reagent according to the period when the sample liquid is not injected into the carrier water by the sampling valve And controlling means for controlling.

  According to the present invention, in the flow injection analysis, when the target substance is repeatedly determined by repeatedly injecting the sample liquid into the carrier liquid, the target substance in the sample liquid is continuously quantified. By interrupting the supply of reagents in response to a period in which quantification is not performed, the consumption of reagents as a whole can be reduced without lowering the accuracy of quantification, etc., as compared to the case where reagents are continuously supplied. it can.

It is a figure which shows the structure of the flow-injection analyzer of one Embodiment of this invention. It is a figure explaining reagent reduction time. It is a graph which shows the relationship of the water flow days in Example 1, and a 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 can be described which can reduce the amount of reagents used. 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 sample water pipe 21 branched from a raw water line 20 is provided. The sample water pipe 21 is a pipe of sample water branched from the raw water, and the tip of the sample water pipe 21 is connected to the sampling valve 10 (also referred to as an injector or an injection valve). Details of the sampling valve 10 will be described later. The portion downstream of the sampling valve 10, including the sampling valve 10, has a configuration as a flow injection analysis (FIA) device and is actually a portion involved in the determination of urea. As described later, the pump P4 is connected to the sampling valve 10. However, in order to continuously determine the amount of urea, the on-off valve 22 is always open and the pump P4 is always driven. Thus, the sample water always flows through the sample water pipe 21.

  Next, the sampling valve 10 will be described. 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 sample water pipe 21 is connected to the port 2. In addition, a pipe 23 to which a carrier liquid (here, carrier water) is supplied 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. The carrier water is supplied to the pump P1 through the pipe 19 and is sent from the pump P1 to the port 6 through the pipe 23.

  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 sample water piping 21 → port 2 → port 1 → sample loop 12 → port 4 → port 3 and is discharged from the piping 25. When the first state is switched to the second state, the sample water flows from the sample water pipe 21 → port 2 → port 3 and is discharged from the pipe 25. Further, the carrier water is pipe 23 → port 6 → port 1 → sample loop 12 → port 4 → port 5 → flow in the pipe 24 and flow out 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.

  The pipe 24 is supplied with the reagent A stored in the storage tank 41, and the mixing section 43 for mixing the reagent A with the liquid flowing in the pipe 24; the reagent B stored in the storage tank 42 is supplied; A mixing unit 44 for mixing the reagent B with the flowing liquid is provided. Each mixing unit has a function of uniformly mixing the reagent A and the reagent B with the flow of the 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. For example, the peak intensity or peak area of the absorbance near the wavelength of 460 nm is determined by the detector 32. The concentration of urea in the sample water can be determined from the absorbance for the sample water by using the absorbance when the carrier water is flowing as a baseline and determining the calibration curve from the absorbance for the standard solution whose urea concentration is known. 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 this FIA apparatus, a continuous flow of liquid (carrier water or sample water flow) is formed in the reaction coil 31 by repeatedly injecting the sample water into the carrier liquid by the sampling valve 10. The sample water is repeatedly introduced into the reaction coil 31. In the reaction coil 31, a reaction of urea with the reagent A and the reagent B occurs, and by measuring a change in absorbance due to the reaction product, it is possible to continuously quantify urea in the sample water.

  In the case of the conventional FIA apparatus, the reagent A and the reagent B stored in the reservoirs 41 and 42 are continuously supplied as a reagent solution to the carrier water flow in the pipe 24 continuously at a constant flow rate. Ru. Even if the set flow rate as the reagent solution is 0.5 mL / min, 720 mL will be consumed if converted to one day. By the way, in continuous determination of the target substance (here, urea) online, in general, a fixed volume of sample water is taken in by the sampling valve 10 every fixed measurement interval time (for example, 60 minutes), and quantitative operation is performed. . Therefore, within one cycle of the measurement interval time, there is a period in which the sample water does not exist in the downstream portion as the FIA device than the sampling valve 10. This period is a period in which the supply of the reagent may be stopped since the quantitative operation is not performed.

  Therefore, in the FIA device of the present embodiment, when the quantitative determination of urea is repeatedly performed, the supply of the reagent A and the reagent B is interrupted corresponding to the period when the quantitative determination of urea is not performed in this repetition. This reduces the consumption of reagent A and reagent B when urea in the sample water is continuously quantified over a long period of time. The reduction of the consumption amount of the reagent A and the reagent B means that if the amount of reagent prepared and stored in the storage tanks 41 and 42 is the same as the conventional apparatus, the reagent in the storage tanks 41 and 42 is compared to the conventional apparatus. It means that the period in which A and reagent B are stored becomes long. Since each reagent has to be stored in the reservoirs 41 and 42 for a long period of time as described above, it is particularly preferable to dispose the reservoirs 41 and 42 inside the refrigeration unit 40 as described above in order to prevent deterioration of the reagents. In the following description, a period in which each reagent is supplied to the reaction coil 31, more specifically, a period in which each reagent is supplied via the mixing units 43 and 44 is a first period, and the reaction coil 31 for each reagent is A period in which the supply of the reagents is interrupted, more specifically, a period in which the supply of each reagent via the mixing units 43 and 44 is stopped is referred to as a second period.

  Next, an example of the configuration for interrupting the supply of the reagent A and the reagent B will be described. When the supply of the reagent A and the reagent B is interrupted, if these reagents do not merge with the liquid flowing in the pipe 24 at the mixing sections 43 and 44, the flow rate of the liquid flowing into the reaction coil 31 decreases accordingly. The state of the flow in the reaction coil 31 may change, which may impair the stability of the entire apparatus or may adversely affect the accuracy of determination. Further, simply stopping the pumps P2 and P3 and stopping the supply of the reagent A and the reagent B will continue to collect these reagents in the pumps P2 and P3 and the pipes 26 and 27. These continuously accumulated reagents may adversely affect the accuracy of quantification when the supply of reagent A and reagent B is resumed. Therefore, in the present embodiment, during the second period in which the supply of the reagent is interrupted, the flow rate in the reaction coil 31 does not change, and the reagent does not stay in the pumps P2 and P3 and the pipes 26 and 27. In place of each reagent, carrier water having the same flow rate as the flow rate of the reagent (in other words, the flow rate of the reagent in the first period) would be supplied to the pipe 24 if the supply was not interrupted. It supplies to piping 24 via parts 43 and 44. Therefore, in the apparatus shown in FIG. 1, a three-way valve 55 for switching between reagent A and carrier water and a three-way valve 56 for switching between reagent B and carrier water are provided. Each of the three-way valves 55, 56 has one common port and two supply ports, and selects one of the two supply ports to discharge the liquid supplied to the selected supply port from the common port. It is something that can be done. The reservoirs 41 and 42, the three-way valves 55 and 56, and the pumps P2 and P3 constitute an addition means. The flow rate of the carrier water flowing to the mixing units 43 and 44 via the pipes 26 and 27 in the second period is different from the flow rate in the first period if the quantitative accuracy and the stability of the device are less affected. It may be

  A pipe 51 is branched from a pipe 19 that supplies carrier water to the pump P 1, and an open / close valve 52 is provided at the tip of the pipe 51. A pipe 53 is connected to the outlet of the on-off valve 52, and a pipe 54 branches from the pipe 53. The pipes 53 and 54 are for supplying carrier water to the three-way valves 55 and 56, respectively. One of the two supply ports of the three-way valve 55 is connected to the pipe 53, and the other supply port is connected to the storage tank 41 of the reagent A via the pipe 45. The common port of the three-way valve 55 is connected to the mixing unit 43 via the pipe 26, and the pipe 26 is provided with a pump P2 that always operates at a flow rate specified for the reagent A. Similarly, one of the two supply ports of the three-way valve 56 is connected to the pipe 54, and the other supply port is connected to the reservoir 42 of the reagent B through the pipe 46. The common port of the three-way valve 56 is connected to the mixing unit 44 via the pipe 27, and the pipe 27 is provided with a pump P3 that always operates at a flow rate prescribed for the reagent B.

  Further, the FIA device is provided with a control unit 50 that controls the sampling valve 10, the on-off valve 52, and the three-way valves 55, 56. The control unit 50 corresponds to the control means, and closes the on-off valve 52 in the first period in which each reagent is supplied, and the three-way valves 55, 56 respectively supply the supply ports of the reagent A and the reagent B. Control to select. Further, in the second period in which the supply of each reagent is interrupted, the control unit 50 opens the on-off valve 52 and controls the three-way valves 55 and 56 to select the carrier water supply port. As a result, the reagent A is fed to the mixing unit 43 at a predetermined flow rate through the three-way valve 55 and the pump P2 in the first period, and is mixed with the carrier water in the mixing unit 43. In the second period, the carrier water is fed from the three-way valve 55 to the mixing portion 43 through the pump P2, but since the pump P2 is always operated at the prescribed flow rate, the mixing portion is operated during the first period. The carrier water is sent to the mixing unit 43 at the same flow rate as the reagent A supplied to 43, and the carrier water is additionally supplied to the liquid in the pipe 24, ie, the carrier water. Similarly, in the first period, the reagent B is fed to the mixing unit 44 at a predetermined flow rate via the three-way valve 56 and the pump P3 and mixed with the carrier water. In the second period, carrier water is fed from the three-way valve 56 through the pump P3 to the mixing portion 44 at the same flow rate as the reagent B supplied to the mixing portion 44 in the first period, and this carrier water is , And carrier water in the piping 24 is additionally supplied. Thus, in the FIA device of the present embodiment, the flow rate of the liquid flowing through the reaction coil 31 does not change between the first period in which each reagent is supplied and the second period in which the reagent is not supplied. Become. In the present embodiment, the carrier water is supplied to the three-way valves 55 and 56, but a storage tank for storing a liquid having the same water quality as the carrier water is installed in a separate line from the carrier water. 55, 56 may be additionally supplied instead of the reagent. The point is that the liquid other than the reagent may be supplied to the mixing units 43 and 44 through the pumps P2 and P3 and the pipes 26 and 27 in the second period.

  Here, the timing of interrupting the supply of the reagent A and the reagent B will be described. When performing quantification repeatedly by the FIA method, the sample water already in the sample loop 12 of the sampling valve 10 starts to flow into the pipe 24 by switching the sampling valve 10 from the first state to the second state described above. Thus, the time period until sample water or reaction product is completely discharged from the detector 32 is a time period necessary for quantifying the target substance, and this one cycle is called one cycle measurement time. The one cycle measurement time is a value which is determined naturally by the configuration and dimensions of the apparatus, the combination of the target substance and the reagent, the flow rate setting value and the like independently of the measurement interval time. Even if the supply of reagents is not interrupted, in principle, the measurement interval time can not be shorter than one cycle measurement time. It is necessary to continue supplying the reagent A and the reagent B during the period of one cycle measurement time. In addition, when the supply of each reagent is resumed from the state where the supply of each reagent was interrupted, it is not possible to measure the sample water immediately, and it is necessary to wait until the state in the FIA apparatus is stabilized. The time from when the supply of each reagent is resumed to when the condition in the apparatus becomes stable and the sample water can be quantified is called the stabilization time.

  In the case of interrupting the supply of reagents, it is necessary to quantify the sample water after the stabilization time has elapsed after the interruption. For quantifying the sample water, the above-described one cycle measurement time is required. Therefore, in order to interrupt the supply of the reagent as described in this embodiment, it is necessary that the sum of one cycle measurement time and the stabilization time be shorter than the measurement interval time. FIG. 2 shows such a relationship of time. The remaining time after subtracting the sum of one cycle measurement time and the stabilization time from the measurement interval time is the reagent reduction time, that is, the second period in which the supply of the reagent can be interrupted. Since it is necessary to continue the supply of each reagent in one cycle measurement time and stabilization time, these correspond to the first period. Assuming that the state in the apparatus is stable in the initial state, each measurement interval time starts with one cycle measurement time, and subsequently, the reagent reduction time and the stabilization time are arranged in this order. According to the present embodiment, as compared with the case where the reagent is continuously supplied as in the conventional case, the value as a whole is obtained by dividing the reagent reduction time (that is, the second period) by the measurement interval time. Reagent consumption can be reduced.

  The control unit 50 determines whether the sum of one cycle measurement time and the stabilization time is shorter than the measurement interval time, if the interval for performing quantification, that is, the measurement interval time, is set to perform continuous quantification. To switch the first state of the sampling valve 10 from the first state to the second state at the start of the one cycle measurement time, and supply each reagent in the first period, and each reagent in the second period. Control of the on-off valve 52 and the three-way valves 55, 56 so as to interrupt the supply of On the other hand, when the sum of the one cycle measurement time and the stabilization time is not shorter than the set measurement interval time, the control unit 50 sets the sampling valve 10 to the first state from the first state at the start time of one cycle measurement time. The switching valve 52 is kept closed and the three-way valves 55 and 56 are controlled so as to always select the reagent so as to supply each reagent constantly while switching to the state of 2. In this case, after the end of the one-cycle measurement time, the idle time continues to be supplied with the reagent until the end of one measurement interval time.

  If all the sample water already in the sample loop 12 has flowed out to the pipe 24 regardless of the interruption of the supply of the reagent, the sampling valve 10 is in the original state, ie, within the 1 cycle measurement time. It is possible to return to the state of 1. However, as the sampling water flow is interrupted with the operation of the sampling valve 10 and this may adversely affect the reaction and absorbance measurement, The state may be returned after the end of one cycle measurement time.

  In the apparatus of the present embodiment, the urea in the sample water can be continuously measured on-line continuously by the colorimetric method using diacetyl monoxime, utilizing the FIA method. At this time, by setting a period for interrupting the supply of the reagent within a range that does not affect the measurement, it is possible to reduce the consumption amount of each reagent when performing long-term continuous quantification. Furthermore, by using, as the reagent A (diacetyl monoximetic acid solution) and the reagent B (antipyrin containing reagent solution) used for the reaction, in particular, the reagent B maintained at 20 ° C. or lower after preparation of those reagents It becomes possible to perform stable determination of urea continuously over a long period of time. In the above description, the supply of both the reagent A and the reagent B is interrupted in the second period, but the supply of either one may be interrupted. Although the case of using two reagents is described, the number of reagents used for analysis is not limited to two, and is limited to those used in the colorimetric analysis of urea using diacetyl monoxime It is not a thing.

  The invention will now be described in more detail by way of examples. Here, experimental results showing the effects of refrigerated reagent A and reagent B will be described.

Example 1
The FIA apparatus shown in FIG. 1 was assembled. However, a portion from the line 20 to the flow meter FI is not provided, and the sample water is directly supplied to the sampling valve 10. Further, without the pipes 51, 53, 54, the on-off valve 52 and the three-way valves 55, 56, the reagent A in the storage tank 41 is directly supplied to the mixing unit 43 via the pump P2, and the reagent B in the storage tank 42 is a pump It was made to be supplied directly to the mixing part 44 via P3. Therefore, the reagent A and the reagent B are always supplied to the pipe 24 continuously.

  The standard solution prepared to have a urea concentration of 60 ppb was continuously supplied to the sampling valve 10 as sample water. And the continuous monitoring of the urea concentration was performed about this 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 standard solution. In this example 1, 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, the measured values when the same standard solution is measured with the peak intensity as 100% when measuring the 60 ppb urea standard solution immediately after preparing the reagents A and B and storing them in the storage tanks 41 and 42, respectively. Shows how it changed with the passage of time.

  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 2)
After preparing the reagent B (antipyrin-containing reagent solution) in the same manner as in Example 1, it 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 1. 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 1 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 3)
The same test as in Example 2 was conducted except that the reagent A (diacetyl monoximetic acid solution) in Example 2 was stored at the same storage temperature as the reagent B (antipyrin-containing reagent solution) in Example 2. .

  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 22, 52 on-off valve 31 Reaction coil 32 Detector 40 Refrigeration part 41, 42 Storage tank 43, 44 Mixing part 50 Control part 55, 56 Three-way valve

Claims (10)

A flow injection analysis method in which a continuous flow of liquid is formed in a reaction coil, and target substances in a sample solution are continuously quantified based on the reaction with a reagent in the reaction coil,
The target substance is repeatedly quantified by repeatedly introducing the sample solution into the reaction coil in which the carrier solution flows.
The flow injection analysis method of interrupting supply of the reagent to the reaction coil corresponding to a period in which the target substance is not quantified in the repetitive execution.   2. The method according to claim 1, wherein a liquid other than the reagent is supplied instead of the reagent via a pump and a pipe used for supplying the reagent during a period in which the supply of the reagent to the reaction coil is interrupted. Flow injection analysis method.   A period in which the reagent is supplied to the reaction coil is a first period, and a period in which the supply of the reagent to the reaction coil is interrupted is a second period, from the introduction of the sample solution to the reagent The sum of the time required for completion of the reaction and the completion of the determination and the time required for the system to become stable as the second period is switched to the first period is the repetition of the sample solution. 3. The flow injection analysis method according to claim 2, wherein the supply of the reagent to the reaction coil is interrupted when it is shorter than the introduction interval.   The flow injection analysis method according to any one of claims 1 to 3, wherein the sample solution 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 4, wherein after preparing the reagent, at least one of the reagents is refrigerated. A flow injection analyzer which forms a continuous liquid flow in a reaction coil and continuously quantifies a target substance in a sample liquid based on a reaction with a reagent in the reaction coil,
A sampling valve for injecting a fixed amount of the sample liquid to the carrier liquid flowing toward the reaction coil;
Addition means for adding a reagent to the carrier liquid into which the sample liquid has been injected at a position between the sampling valve and the reaction coil;
The sampling valve is controlled to repeat the injection of the sample solution into the carrier water, and the addition of the reagent is interrupted in response to a period during which the sample liquid is not injected into the carrier water by the sampling valve. Control means for controlling the addition means;
Flow injection analyzer.   The addition means includes a storage tank for storing the reagent, a valve for selecting one of the storage tank and a supply source of the liquid other than the reagent, and a pump for feeding the liquid selected by the valve. The flow injection analyzer according to claim 6, wherein is controlled by the control means.   The control means determines that the reaction with the reagent is completed after the introduction of the sample solution, with the period for adding the reagent as a first period and the period for which the addition of the reagent is interrupted as a second period. The sum of the time taken to complete the process and the time taken for the system to stabilize with switching from the second period to the first period is shorter than the interval of the repeated introduction of the sample solution 8. The flow injection analyzer according to claim 6, wherein the supply of the reagent to the reaction coil is interrupted.   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, further comprising cooling means for cooling the reagent.

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