JP6982476B2 - Flow injection analysis method and equipment - Google Patents

Description

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

Flow injection analysis, which forms a continuous flow of liquid in a thin tube, injects the sample solution into it to cause a reaction with a reagent, and measures the concentration of reaction products on the secondary side of the tube, is a sample. It is widely used for quantitative analysis of target substances in liquids. The thin tube where the reaction takes place is generally called the reaction coil. In a general flow injection device, the sample liquid is injected into the carrier liquid so as to replace a part of the continuous flow of the carrier liquid with the sample liquid, and the reagent liquid prepared separately from this is continuously used as the carrier liquid. It is configured to be mixed and guided into the reaction coil, and the reagent and the target substance are reacted in the reaction coil. For example, Patent Document 1 discloses that analysis by a colorimetric method using diacetylmonooxime is performed by flow injection analysis in order to continuously monitor a trace amount of urea concentration in a sample water.

The quantification by the colorimetric method using diacetylmonooxime is a well-known method for quantifying urea, and is described in, for example, a hygiene test method (Non-Patent Document 1). In the colorimetric method using diacetylmonooxime, other reagents (for example, antipyrine + sulfuric acid solution, semicarbazide hydrochloride aqueous solution, manganese chloride + potassium nitrate aqueous solution, sodium dihydrogen phosphate + sulfuric acid solution, etc.) are used for the purpose of promoting the reaction. Can be used together. When antipyrine is used in combination, diacetylmonooxime is dissolved in an acetate solution to prepare a diacetylmonooxime acetate 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 diacetylmonooxime acetic acid solution and an anlipylin-containing reagent solution are sequentially mixed with sample water, the absorbance at a wavelength of around 460 nm is measured, and quantification is performed by comparison with a standard solution. The method for quantifying urea by the colorimetric method using diacetylmonooxime was originally intended for the quantification of urea in pool water or public bath water, for example, and is described in Patent Document 1 in this method. By measuring the absorbance by applying the flow injection analysis as described above, urea can be continuously quantified in a concentration range of ppb or less to several ppm.

Japanese Unexamined Patent Publication No. 2000-338099

Pharmaceutical Society of Japan, Hygiene Test Method, Commentary 1990.4.2.12.3 (13) 1 (1990 edition, 4th printing supplement (1995), p1028), 1995

Consider the case where the target substance is continuously quantified online using flow injection analysis. In this case, the target substance in the sample solution is quantified at regular time intervals. One of the characteristics of the flow injection method is that the amount of reagent can be small, but in the case of continuous quantification over a long period of time, for example, weeks or months, the amount of reagent consumed throughout the period is It will be enormous. It is required to reduce the amount of reagents consumed when continuously quantifying by flow injection analysis. Even if the flow rate of the reagent solution is 0.5 mL / min, the reagent solution consumed in one day is 720 mL, which exceeds 20 L in one month.

An object of the present invention is to provide a flow injection analysis method and an apparatus capable of reducing the amount of reagent 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 the target substance in the sample liquid is continuously quantified based on the reaction with the reagent in the reaction coil. Then, by repeating the introduction of the sample liquid into the reaction coil through which the carrier liquid flows, the quantification of the target substance is repeatedly executed, and the reagent is supplied to the reaction coil corresponding to the period during which the quantification of the target substance is not performed in the repeated execution. To interrupt.

The flow injection analyzer of the present invention is a flow injection analyzer that forms a continuous flow of liquid in the reaction coil and continuously quantifies the target substance in the sample liquid based on the reaction with the reagent in the reaction coil. A sampling valve that injects a certain amount of sample liquid into the carrier liquid that flows toward the reaction coil, and an addition that adds a reagent to the carrier liquid into which the sample liquid is injected at the position between the sampling valve and the reaction coil. The means and the sampling valve are controlled so as to repeat the injection of the sample liquid into the carrier water, and the addition means is used so as to interrupt the addition of the reagent corresponding to the period during which the sample liquid is not injected into the carrier water by the sampling valve. It has a control means for controlling.

According to the present invention, in the flow injection analysis, the target substance is repeatedly quantified by repeatedly injecting the sample solution into the carrier liquid, and the target substance is continuously quantified in the sample liquid. By interrupting the supply of the reagent corresponding to the period during which the quantification is not performed, it is possible to reduce the consumption of the reagent as a whole without deteriorating the quantification accuracy, etc., as compared with the case where the reagent is continuously supplied. 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 the reagent reduction time. It is a graph which shows the relationship between the number of days of water flow and the peak intensity in Example 1. FIG.

Next, an embodiment 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 small amount of urea contained in this sample solution (here, it can be said to be sample water because it is water) is continuously quantified online as a target substance. The present invention that can reduce the amount of the reagent used will be described by taking a case as an example. Of course, the target substance to be quantified in the present invention is not limited to urea, and the sample solution containing the target substance is not limited to water. For example, the FIA apparatus of the present embodiment can be connected to some kind of water treatment system (it can be said that the pure water production apparatus is also a kind of water treatment system) to 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, and in this line 20, raw water is sent by a pump P0. A sample water pipe 21 branching from the raw water line 20 is provided. The sample water pipe 21 is a pipe for sample water branched from raw water, and the tip of the sample water pipe 21 is connected to a 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 from the sampling valve 10, including the sampling valve 10, has a configuration as a flow injection analysis (FIA) device and is actually a portion related to the determination of urea. As will be described later, the pump P4 is connected to the sampling valve 10, but the on-off valve 22 is always open and the pump P4 is constantly driven in order to continuously quantify urea. As a result, 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 hexagonal valve 11 and a sample loop 12. The six-way valve 11 includes six ports indicated by circled numbers in the illustration. The sample water pipe 21 is connected to the port 2. Further, a pipe 23 to which the carrier liquid (here, carrier water) is supplied is connected to the port 6, and a pipe 25 for draining the sample water via the pump P4 is connected to the port 3. A sample loop 12 for collecting a predetermined volume of sample water is connected between the port 1 and the port 4. One end of the pipe 24, which is the outlet of the sampling valve 11, is connected to the port 5. The carrier water is water that does not substantially contain urea, for example, pure water. The carrier water is supplied to the pump P1 via the pipe 19, and is sent from the pump P1 to the port 6 via the pipe 23.

Assuming that the communication between the port X and the port Y in the hexagonal valve 11 is expressed as (XY), the hexagonal valve 11 is (1-2), (3-4), (5-6). The first state and the second state (2-3), (4-5), and (6-1) can be switched. In FIG. 1, the connection relationship between the ports in the first state is shown by a solid line, and the connection between the ports in the second state is shown by a dotted line. In the first state, the carrier water flows in the order of the pipe 23 → the port 6 → the port 5 → the pipe 24 and flows out from the sampling valve 10 to the downstream side. The sample water flows from the sample water pipe 21 → port 2 → port 1 → sample loop 12 → port 4 → port 3 and is discharged from the pipe 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, and the carrier water flows from the pipe 23 → port 6 → port. It flows in the order of 1 → sample loop 12 → port 4 → port 5 → piping 24, and flows out to the downstream side. At this time, the sample water that has already flowed in in the first state and fills the inside of the sample loop 12 flows from the port 5 to the pipe 24 prior to the carrier water and flows to the downstream side of the sampling valve 10. It flows. The volume of sample water flowing through the pipe 24 is defined by the sample loop 12. Therefore, by repeatedly switching between the first state and the second state (for example, by rotating the hexagonal valve 11 in the direction of the arrow in the figure), a predetermined volume of sample water can be repeatedly sent to the pipe 24. The switching between the first state and the second state can be performed at predetermined time intervals in consideration of the residence time required for the reaction described later and the time until urea is detected by the detector 32. It is also possible to detect that the sample water introduced into the detector 32 has been discharged from the detector 32 and perform switching. In this way, by automatically switching between the first state and the second state, urea can be continuously quantified.

In this device, the FIA method is applied to the quantification of urea by the colorimetric method using diacetylmonooxime. Therefore, as a reaction reagent used for the quantification of urea, a diacetylmonooxime acetic acid solution (hereinafter, also referred to as reagent A) and an antipyrine-containing reagent solution (hereinafter, also referred to as reagent B) are used. Here, a case where an antipyrine-containing reagent solution is used as a reagent used in combination with diacetylmonooxime will be described, but the reagent used in combination with diacetylmonooxime is not limited to the antipyrine-containing reagent solution. Reagent A and Reagent B are stored in storage tanks 41 and 42, respectively.

The present inventors prepared these reagents, and when they were kept at room temperature for a long period of time (for example, several days or more) for continuous quantification of urea, the peak intensity in the absorbance measurement decreased, and this peak. It has been found that the decrease in strength can be prevented by refrigerating the reagent (particularly reagent B). In order to perform stable quantification, it is preferable that the peak intensity in the absorbance measurement does not decrease. Therefore, in the FIA apparatus of the present embodiment, the storage tanks 41 and 42 are provided in the refrigerating section 40. Reagent A is prepared by dissolving diacetylmonooxime in an acetic acid solution, but when the refrigerating section 40 is provided, the preparation itself is performed in the storage tank 41, or reagent A is stored in the storage tank 41 after its preparation. do. Similarly, reagent B is prepared by dissolving antipyrine in, for example, sulfuric acid, but the preparation itself is performed in the storage tank 42, or reagent B is stored in the storage tank 42 after its preparation. The refrigerating section 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 kept at 20 ° C. or lower, preferably 3 ° C. or higher and 20 ° C. Hereinafter, it is more preferably maintained at 5 ° C. or higher and 15 ° C. or lower. The storage tank 41 for storing the reagent A does not necessarily have to be arranged in the refrigerating section 40 as long as it can be stored in a light-shielded manner. Even if the refrigerating temperature of the reagent is less than 5 ° C., it does not matter as long as crystals do not precipitate in the reagent. According to the hygiene test method (Non-Patent Document 1), an antipyrine sulfuric acid 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 it is redissolved even if crystals are precipitated and returned to room temperature. Although it is stated that refrigerated storage is not suitable because it does not, the present inventors have experimentally confirmed that the antipyrine sulfate solution prepared according to the hygiene test method does not crystallize even at 3 ° C.

Reagent A stored in the storage tank 41 is supplied to the pipe 24 to mix the reagent A with the liquid flowing in the pipe 24, and reagent B stored in the storage tank 42 is supplied to the pipe 24. A mixing unit 44 for mixing the reagent B with the flowing liquid is provided. Each of the mixing portions has a function of uniformly mixing the reagent A and the reagent B with respect to 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 bath 30. The reaction coil 31 causes a color reaction between urea and diacetylmonooxime in the presence of antipyrine, and its length and the flow velocity inside the reaction coil 31 are the residence time required for the reaction. It is appropriately selected according to the above. The reaction constant temperature bath 30 raises the temperature of the reaction coil 31 to a temperature suitable for the reaction. For example, the reaction coil 31 is heated to a temperature of 50 ° C. or higher and 150 ° C. or lower, preferably 90 ° C. or higher and 120 ° C. or lower. ..

At the end, that is, the outlet of the reaction coil 31, a detector 32 for measuring the absorbance of the color developed in the liquid by the color-developing reaction is provided for the liquid flowing out of the reaction coil 31. The detector 32 is used to determine, for example, the peak intensity or peak area of the absorbance at a wavelength of around 460 nm. By using the absorbance when the carrier water is flowing as the baseline and obtaining the calibration curve from the absorbance with respect to a standard solution having a known urea concentration, the concentration of urea in the sample water can be obtained from the absorbance with respect to the sample water. At the outlet of the detector 32, a back pressure coil 33 that applies back pressure to the pipeline from the pump P1 to the detector 32 via the sampling valve 10, the pipe 24, and the reaction coil 31 is provided. 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 will be repeatedly introduced into the reaction coil 31. A reaction between urea and Reagent A and Reagent B occurs in the reaction coil 31, and urea in sample water can be continuously quantified by measuring the change in absorbance due to this reaction product.

In the conventional FIA apparatus, the reagents A and B stored in the storage tanks 41 and 42 are constantly and continuously supplied to the carrier water flow in the pipe 24 at a constant flow rate as reagent liquids. To. Even if the set flow rate as the reagent solution is 0.5 mL / min, 720 mL will be consumed in terms of daily conversion. By the way, in the online continuous quantification of a target substance (here, urea), in general, a constant volume of sample water is taken in by a sampling valve 10 at a constant measurement interval time (for example, 60 minutes), and a quantification operation is performed. .. Therefore, in one cycle of the measurement interval time, there is a period in which the sample water does not exist in the portion downstream of the sampling valve 10 as the FIA device. Since the quantitative operation is not performed during this period, it can be said that the supply of the reagent may be stopped.

Therefore, in the FIA apparatus of the present embodiment, when the quantification of urea is repeatedly executed, the supply of the reagent A and the reagent B is interrupted corresponding to the period during which the quantification of urea is not performed in this repetition. This reduces the consumption of Reagent A and Reagent B when the urea in the sample water is continuously quantified over a long period of time. The reduction in the consumption of Reagent A and Reagent B means that if the amount of reagent prepared and stored in the storage tanks 41 and 42 is the same as that of the conventional device, the reagent in the storage tanks 41 and 42 is compared with that of the conventional device. This means that A and reagent B can be stored for a longer period of time. Since each reagent must be stored in the storage tanks 41 and 42 for such a long period of time, it is particularly preferable to arrange the storage tanks 41 and 42 inside the refrigerating section 40 as described above in order to prevent deterioration of the reagents. In the following description, the period in which each reagent is supplied to the reaction coil 31, more specifically, the period in which each reagent is supplied via the mixing units 43 and 44 is defined as the first period, and the reaction coil 31 of each reagent is used. The period during which the supply to the reagents is suspended, more specifically, the period during which the supply of each reagent via the mixing units 43 and 44 is stopped is defined as the 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 through the pipe 24 at the mixing portions 43 and 44, the flow rate of the liquid flowing into the reaction coil 31 decreases by that amount. The state of the flow in the reaction coil 31 may change, which may impair the stability of the entire apparatus or adversely affect the quantification accuracy. Further, if the pumps P2 and P3 are simply stopped to stop the supply of the reagents A and B, these reagents will continue to accumulate in the pumps P2 and P3 and the pipes 26 and 27. These accumulated reagents may adversely affect the quantification accuracy when the supply of the reagents A and B is restarted. Therefore, in the present embodiment, the flow rate in the reaction coil 31 does not change during the second period in which the supply of the reagent is interrupted, and the reagent does not stay in the pumps P2 and P3 and the pipes 26 and 27. In addition, carrier water at the same flow rate as the reagent flow rate (in other words, the reagent flow rate in the first period) that would have been supplied to the pipe 24 if the supply had not been interrupted was mixed instead of each reagent. It is supplied to the pipe 24 via the portions 43 and 44. Therefore, in the apparatus shown in FIG. 1, a three-way valve 55 for switching between the reagent A and the carrier water and a three-way valve 56 for switching between the reagent B and the carrier water are provided. Each of the three-way valves 55 and 56 has one common port and two supply ports, and one of the two supply ports is selected to discharge the liquid supplied to the selected supply port from the common port. It is something that can be done. The addition means is composed of storage tanks 41, 42, three-way valves 55, 56, and pumps P2, P3. If the effect on the quantification accuracy and the stability of the device is small, the flow rate of the carrier water flowing to the mixing portions 43 and 44 via the pipes 26 and 27 in the second period is different from the flow rate in the first period. May be.

A pipe 51 is provided by branching from a pipe 19 that supplies carrier water to the pump P1, and an on-off 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 the 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. Of the two supply ports of the three-way valve 55, one supply port is connected to the pipe 53, and the other supply port is connected to the reagent A storage tank 41 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, of the two supply ports of the three-way valve 56, one supply port is connected to the pipe 54, and the other supply port is connected to the storage tank 42 of the reagent B via 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 specified for the reagent B.

Further, the FIA apparatus is provided with a control unit 50 for controlling the sampling valve 10, the on-off valve 52, and the three-way valves 55 and 56. The control unit 50 corresponds to the control means, and in the first period of supplying each reagent, the on-off valve 52 is closed, and the three-way valves 55 and 56 operate the supply ports of the reagents A and B, respectively. Control to select. Further, 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 in the second period during which the supply of each reagent is interrupted. As a result, in the first period, the reagent A is fed to the mixing unit 43 at a predetermined flow rate via the three-way valve 55 and the pump P2, and is mixed with the carrier water in the mixing unit 43. In the second period, carrier water is supplied from the three-way valve 55 to the mixing unit 43 via the pump P2, but since the pump P2 is always operating at a specified flow rate, the mixing unit during the first period. The carrier water will be sent to the mixing unit 43 at the same flow rate as the reagent A supplied to the 43, and the carrier water will be additionally supplied to the liquid in the pipe 24, that is, 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 supplied from the three-way valve 56 to the mixing unit 44 via the pump P3 at the same flow rate as the reagent B supplied to the mixing unit 44 during the first period, and the carrier water is supplied. , Is additionally supplied to the carrier water in the pipe 24. In this way, in the FIA apparatus 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 the reagents are supplied and the second period in which the reagents are 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 the liquid having the same water quality as the carrier water is installed on a line different from the carrier water, and the liquid in the storage tank is used as the three-way valve. It may be additionally supplied to 55 and 56 instead of the reagent. In short, it suffices that the liquid other than the reagent is supplied to the mixing portions 43 and 44 via the pumps P2 and P3 and the pipes 26 and 27 in the second period.

Here, the timing at which the supply of the reagent A and the reagent B is interrupted will be described. When the quantification is repeatedly performed by the FIA method, by switching the sampling valve 10 from the first state to the second state described above, the sample water already in the sample loop 12 of the sampling valve 10 starts to flow into the pipe 24. Therefore, the period until the sample water and the reaction product are completely discharged from the detector 32 is a period required for the quantification of the target substance, and this one cycle is called one cycle measurement time. The one-cycle measurement time is a value that is independently determined by the configuration and dimensions of the device, the combination of the target substance and the reagent, the flow rate set value, and the like, independently of the measurement interval time. In principle, the measurement interval time cannot be shorter than the one-cycle measurement time even when the reagent supply is not interrupted. It is necessary to continue supplying Reagent A and Reagent B during the period of one cycle measurement time. Further, when the supply of each reagent is restarted from the state where the supply of each reagent is interrupted, the sample water cannot be quantified immediately, and it is necessary to wait until the state in the FIA apparatus stabilizes. The time from when the supply of each reagent is restarted until the state in the apparatus becomes stable and the sample water can be quantified is called the stable time.

When the supply of the reagent is interrupted, it is necessary to quantify the sample water after a stable time has elapsed after the interruption. The above-mentioned one-cycle measurement time is required to quantify the sample water. Therefore, in order to interrupt the supply of the reagent as described in the present embodiment, it is necessary that the sum of the one-cycle measurement time and the stabilization time is shorter than the measurement interval time. FIG. 2 shows such a relationship between each time. The remaining time obtained by subtracting the sum of the one-cycle measurement time and the stabilization time from the measurement interval time is the reagent reduction time, that is, the second period during which the reagent supply can be interrupted. Since it is necessary to continue supplying each reagent in one cycle measurement time and stable 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, followed by the reagent reduction time and the stabilization time 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 reagent reduction time (that is, the second period) is divided by the measurement interval time to obtain the value as a whole. Reagent consumption can be reduced.

When the interval for performing quantification, that is, the measurement interval time is set for continuous quantification, the control unit 50 determines whether the sum of the one-cycle measurement time and the stable time is shorter than the measurement interval time, and if it is short. At the start of one cycle measurement time, the sampling valve 10 is switched from the first state to the second state, and each reagent is supplied in the first period, and each reagent is supplied in the second period. The on-off valve 52 and the three-way valves 55 and 56 are controlled so as to interrupt the supply of the valve. On the other hand, when the sum of the one-cycle measurement time and the stable time is not shorter than the set measurement interval time, the control unit 50 sets the sampling valve 10 from the first state at the start of the one-cycle measurement time. While switching to the state of 2, the on-off valve 52 is kept closed so that each reagent is constantly supplied, and the three-way valves 55 and 56 are controlled so that the reagent is always selected. In this case, after the end of one cycle measurement time, until the end of one measurement interval time, the idle time during which the reagent is continuously supplied is set.

After all the sample water already in the sample loop 12 has flowed out to the pipe 24 regardless of whether or not the supply of the reagent is interrupted, the sampling valve 10 is in the original state, that is, in the first cycle measurement time even within one cycle measurement time. Although it can be returned to the state of 1, the operation of the sampling valve 10 causes a momentary interruption of the carrier water flow, which may adversely affect the reaction and the absorbance measurement. Therefore, the sampling valve 10 is used as the original. The state may be returned after the end of one cycle measurement time.

In the apparatus of this embodiment, the FIA method is used, and urea in the sample water can be continuously measured online by a colorimetric method using diacetylmonooxime. At this time, by setting a period during which the supply of reagents is interrupted within a range that does not affect the measurement, it is possible to reduce the consumption of each reagent when performing continuous quantification over a long period of time. Further, as the reagent A (diacetylmonooxime acetic acid solution) and the reagent B (antipyrine-containing reagent solution) used for the reaction, particularly the reagent B, which was maintained at 20 ° C. or lower after the preparation of these reagents, was used. , It becomes possible to stably quantify urea for 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 in the analysis is not limited to two, and is limited to those used in the colorimetric analysis of urea using diacetylmonooxime. It's not something.

Next, the present invention will be described in more detail by way of examples. Here, the experimental results showing the effect of refrigerating the reagent A and the reagent B will be described.

(Example 1)
The FIA apparatus shown in FIG. 1 was assembled. However, the portion from the line 20 to the flow meter FI was not provided, and the sample water was directly supplied to the sampling valve 10. Further, without providing 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 pumped. It was made to be directly supplied to the mixing unit 44 via P3. Therefore, the reagent A and the reagent B are constantly and continuously supplied to the pipe 24.

A standard solution having a urea concentration of 60 ppb can be continuously supplied to the sampling valve 10 as sample water. Then, the urea concentration was continuously monitored for this standard solution. Here, it was investigated how the urea concentration obtained as the measured value of the detection peak of the absorbance in the detector 32 changes when the standard solution is continuously measured. In this Example 1, 2 g of diacetylmonooxime is dissolved in 100 mL of 10% acetic acid to prepare Reagent A (diacetylmonooxime acetic acid solution), 0.2 g of antipyrine is taken, and the total amount is 100 mL. Reagent B (anti-sulfuric acid-containing reagent solution) was prepared as a reagent B (reagent solution containing anti-sulfuric acid), and immediately after the preparation, those reagents were stored in the storage tanks 41 and 42, respectively, and each reagent was continuously supplied from the storage tanks 41 and 42 toward the pipe 24. After injecting each reagent into the storage tanks 41 and 42 at the beginning of the continuous measurement, the reagent was not replenished during the continuous measurement. Further, the storage tank 41 of the reagent A was maintained at room temperature. For Reagent B, experiments were conducted in two cases, one was when the storage temperature after preparation was 10 ° C and the other was when the storage temperature was 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 was measured, with the peak intensity when measuring the urea standard solution of 60 ppb immediately after preparing the reagents A and B and storing them in the storage tanks 41 and 42, respectively, as 100%. Shows how has changed over time.

As shown in FIG. 3, when the antipyrine-containing reagent solution (reagent B) was maintained at 25 ° C., the peak intensity gradually decreased, and the peak intensity was 72% during the 10-day operation for continuous measurement. Has dropped to. That is, the quantification of urea could not be performed stably. On the other hand, it was found that when the antipyrine-containing reagent solution was stored in a refrigerator and maintained at 10 ° C., the peak intensity did not decrease even after 10 days of continuous operation, and the continuous quantification of urea could be stably performed over a long period of time. rice field.

(Example 2)
Reagent B (antipyrine-containing reagent solution) was prepared in the same manner as in Example 1, and then stored at 5 ° C., 10 ° C., 15 ° C., 20 ° C. and 25 ° C. for 10 days, respectively. Then, after this storage, the reagent B was supplied to the apparatus of Example 1. Immediately after supplying Reagent B to the device, a standard solution having a urea concentration of 60 ppb was measured using this device, and its peak intensity was determined. At that time, the peak intensity when the standard solution was measured immediately after the preparation of the reagent B was set to 100%. The reagent A (diacetylmonooxime acetic 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, there is almost no decrease in peak intensity when the storage temperature is 5 ° C and 10 ° C, and when stored at 15 ° C, the peak intensity decreases 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 antipyrine-containing reagent solution among the reagents (diacetylmonooxime acetic acid solution and antipyrine-containing reagent solution) used for the reaction should be stored in a refrigerator. In this case, it was found that the temperature of the antipyrine-containing reagent solution is preferably maintained at 20 ° C. or lower, more preferably 3 ° C. or higher and 20 ° C. or lower, and more preferably 5 ° C. or higher and 15 ° C. or lower. ..

(Example 3)
The same test as in Example 2 was carried out except that the reagent A (diacetylmonooxime acetic acid solution) of Example 2 was stored at the same storage temperature as the reagent B (antipyrine-containing reagent solution) of Example 2. ..

When both Reagent A and Reagent B were refrigerated for measurement, the same results as the results of refrigerating only Reagent B for measurement (Table 1) were obtained.

10 Sampling valve 12 Sample loop 22, 52 On-off valve 31 Reaction coil 32 Detector 40 Refrigerator 41,42 Storage tank 43,44 Mixing section 50 Control section 55,56 Three-way valve

Claims (9)

A flow injection analysis method in which a continuous flow of liquid is formed in a reaction coil, and the target substance in the sample liquid is continuously quantified based on the reaction with the reagent in the reaction coil.
Repeatedly perform the determination of the target substance by repeating the introduction of the sample solution by using a sampling valve in pairs to the reaction coil carrier liquid flows,
In the repeated execution, the supply of the reagent to the reaction coil is interrupted corresponding to the period during which the sample liquid is not introduced into the carrier liquid by the sampling valve .
In the period that interrupts the supply to the reaction coil of the reagent, through the pump and pipes used for the supply of the reagent supplying liquid other than the reagent in place of the reagent, flow injection analysis method. The period in which the reagent is supplied to the reaction coil is set as the first period, and the period in which the supply of the reagent is interrupted to the reaction coil is set as the second period. time required until quantification ends the reaction is complete, the system in accordance with the switching from the second period to the first period is the sum of the time required to stabilize, the prior SL repeatedly performed when shorter than the distance between the introduction of the sample solution, interrupts the supply to the reaction coil of the reagent, flow injection analysis method according to claim 1. The flow injection analysis method according to claim 1 or 2 , wherein the sample liquid is water obtained by online connection from a water treatment system. The flow injection analysis method according to any one of claims 1 to 3 , wherein after preparing the reagent, at least one of the reagents is refrigerated. A flow injection analyzer that forms a continuous flow of liquid in a reaction coil and continuously quantifies the target substance in the sample liquid based on the reaction with the reagent in the reaction coil.
A sampling valve that injects a constant amount of the sample liquid into the carrier liquid that flows toward the reaction coil, and
An addition means for adding a reagent to the carrier liquid into which the sample liquid is injected at a position between the sampling valve and the reaction coil.
The sampling valve is controlled so that the injection of the sample liquid into the carrier liquid is repeated, and the addition of the reagent is interrupted by the sampling valve corresponding to the period during which the sample liquid is not injected into the carrier liquid. The control means for controlling the addition means and
Flow injection analyzer with. 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 a liquid other than the reagent, and a pump for sending the liquid selected by the valve. The flow injection analyzer according to claim 5 , wherein is controlled by the control means. In the control means, the period in which the reagent is added is set as the first period, and the period in which the addition of the reagent is suspended is set as the second period, and the reaction with the reagent is completed from the injection of the sample solution and quantified. time required until the end, the sum of the system in accordance with the switching to the first period and the time required to stabilize the second period, the interval of the injection of repeat of the sample solution The flow injection analyzer according to claim 5 or 6 , wherein the supply of the reagent to the reaction coil is interrupted when the time is shorter than that. The flow injection analyzer according to any one of claims 5 to 7 , which is connected online to a water treatment system and uses the water obtained from the water treatment system as the sample liquid to quantify the target substance. The flow injection analyzer according to any one of claims 5 to 8 , further comprising a cooling means for cooling the reagent.

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