JP4581056B2 - Fluoride determination method by ventilation micro-diffusion and its device - Google Patents

Description

The present invention relates to a fluoride determination method by ventilated microdiffusion and an apparatus used therefor.
More specifically, the present invention allows a diffusion solution made of a strong acid to diffuse in a sample such as food, adsorbs and collects the resulting fluoride in the collection solution, and measures the fluoride ion concentration in the collection solution. This is a method for quantifying fluoride in a sample by means of a ventilated micro-diffusion method, which consists of two volume-variable syringes, a reaction tank, and a collection tank containing a collection liquid, and these are connected by a tube. Using the system, the inside of the reaction system is adjusted to negative pressure by the operation of two variable volume syringes, and the gas in the reaction system including the reaction tank and the collection tank is ventilated. Fluoride determination method based on ventilated micro-diffusion and apparatus used therefor, characterized in that fluoride gas generated by diffusion reaction with diffusion liquid is introduced into a collection tank containing the collection liquid and adsorbed on the collection liquid About.
The quantification method and apparatus of the present invention enables reproducible and reliable quantification of fluoride in a sample such as food, and further has extremely high work efficiency, enabling quantification using a large amount of sample. It has various excellent points such as being possible.

In order to obtain the maximum caries prevention effect by systemic application of fluoride and to prevent dental fluorosis due to excessive intake, it is important to estimate the daily fluoride intake in advance. Therefore, there is an urgent need to establish a method for analyzing fluoride in samples such as food. However, fluoride analysis methods for samples containing a large amount of organic substances such as food require special quantitative operations, and there is currently no unified method for accurately analyzing low-concentration fluoride samples such as food samples. is there.
Conventionally, the micro-diffusion method developed by Taves (Non-patent Document 1) has been widely used as a method for analyzing fluoride in foods and biological samples. This method has the following reaction formula:

Diffusion reaction Sample + Perchloric acid → Sample decomposition product + HF …………… (1)
HF + (CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ → (CH ₃ ) ₃ SiF + (CH ₃ ) ₃ SiOH …… (2)
HF + (CH ₃ ) ₃ SiOH → (CH ₃ ) ₃ SiF + H ₂ O …………………… (3)
Collection reaction
_{(CH 3) 3 SiF + NaOH} → (CH 3) 3 SiOH + Na + + F - ............... (4)

As shown in Fig. 3, the sample is reacted with a strong acid such as perchloric acid, and the resulting fluoride (HF gas or TMS gas) is adsorbed and collected by the sodium hydroxide collection solution. The fluoride ion concentration in the sample is measured by an ion electrode method to quantify the fluoride in the sample.
Taves, DR, Talanta, 15: 1015-1023, 1968

This conventional micro-diffusion method is designed to be performed in a fixed sealed space. Therefore, the internal pressure increases due to the expansion of the reaction liquid or gas in the diffusion container, and there is a risk that the reaction fluoride gas leaks out of the diffusion container. Collection of the collected liquid is a batch process, and only one measurement value can be obtained from one sample. In addition, the amount of sample used for a single measurement is limited to a small amount (about 0.5 to 1 g), and ashing may be required as a pretreatment for concentration concentration.
Therefore, the problem of the present invention is that it is possible to avoid the risk that the reaction fluoride gas leaks out of the diffusion container, to provide a large amount of sample for measurement, and to enable quantitative determination of fluoride with high reproducibility and reliability, It is another object of the present invention to provide a fluoride determination method having various excellent points such as extremely high work efficiency and an apparatus used therefor.

As a result of earnest research to solve the above-mentioned problems, the present inventor consists of two volume-variable syringes, a reaction tank and a collection tank containing a collection liquid, and uses a reaction system in which these are connected by a tube, By adjusting the negative pressure in the reaction system by operating two variable volume syringes, and ventilating the gas in the reaction system including the reaction tank and the collection tank, the fluoride in the sample is quantified. The present invention has been completed by finding that the above problems can be solved.
Therefore, in the present invention, a diffusion solution composed of a strong acid is diffused in a sample, and the resulting fluoride is adsorbed to and collected by the collection solution, and the fluoride ion concentration in the collection solution is measured. In the fluoride determination method using ventilated microdiffusion to quantify fluoride,
The reaction system consists of two variable volume syringes, a reaction tank, and a collection tank containing the collection liquid. These are connected by a tube, and the reaction system is adjusted to a negative pressure by operating the two variable volume syringes. And collecting the fluoride gas produced by the diffusion reaction between the sample and the diffusion liquid in the reaction tank by ventilating the gas in the reaction system including the reaction tank and the collection tank. To be adsorbed to the collected liquid,
The present invention relates to a method for quantitative determination of fluoride by ventilated micro-diffusion.

Furthermore, the present invention allows a sample to undergo a diffusion reaction with a diffusion solution composed of a strong acid, adsorbs and collects the resulting fluoride on the collection solution, measures the fluoride ion concentration in the collection solution, and measures the fluoride in the sample. In an apparatus for the determination of fluoride by ventilated microdiffusion,
It consists of two variable volume syringes, a reaction tank and a collection tank, which are connected by a tube to form a reaction system, and the reaction system is adjusted to a negative pressure by operating the two variable volume syringes, and the reaction The gas in the reaction system including the tank and the collection tank can be ventilated, and the fluoride gas generated by the diffusion reaction between the sample and the diffusion liquid in the reaction tank can be introduced into the collection tank. Being
It is related with the apparatus for the fluoride determination by ventilation type microdiffusion characterized by the above-mentioned.

Hereinafter, the quantitative method and apparatus of the present invention will be described in detail with reference to FIG. 1 showing an example of the apparatus of the present invention.
In the fluoride quantification method by the ventilated micro-diffusion of the present invention, it consists of two syringes with a variable volume, a reaction tank, and a collection tank containing a collection liquid. By adjusting the negative pressure in the reaction system by operating two syringes and ventilating the gas in the reaction system including the reaction tank and the collection tank, the diffusion reaction between the sample and the diffusion liquid in the reaction tank The resulting fluoride gas is introduced into a collection tank containing a collection solution and adsorbed by the collection solution, and the fluoride ion concentration in the collection solution is measured to quantify the fluoride in the sample.
In the present invention, the target of the sample may be any sample containing fluoride, for example, biological samples such as blood and saliva, liquid foods such as milk, milk, vegetables, and green tea, and solid foods. Foods with various properties such as
As the diffusion liquid composed of a strong acid that undergoes a diffusion reaction with the sample, a perchloric acid (HClO ₄ ) solution saturated with hexamethyldisiloxane (HMDS) is usually preferably used. In particular, a 5.0 molar perchloric acid solution saturated with hexamethyldisiloxane is preferred. A sodium hydroxide (NaOH) solution is usually used as a collecting liquid for collecting the fluoride gas generated by the diffusion reaction between the sample and the diffusing liquid, and a 0.1 to 0.01 molar sodium hydroxide solution is preferred.
In addition, in the diffusion reaction, it is preferable that a certain concentration of silicone-based antifoaming agent is present in order to facilitate the diffusion reaction. As the silicone-based antifoaming agent, those usually used can be used, and examples thereof include antifoaming silicone TSA737 (manufactured by Toshiba Silicone).

  In the present invention, as shown in the upper left side of FIG. 1, the diffusion liquid is preferably prepared by preparing a diffusion liquid tank 1 composed of a syringe and putting the diffusion liquid 2 in the diffusion liquid tank. The reaction vessel 3 preferably has a cylindrical shape with a constant volume as shown in FIG. It is preferable that the reaction tank 3 is immersed in the constant temperature water tank 4 and set to 40 ° C. to 50 ° C. to cause the sample and the diffusion solution to undergo diffusion reaction. The reaction tank 3 is provided with a tube 5 for introducing the diffusion liquid 2 into the reaction tank 3 so that the diffusion liquid 2 is injected from the diffusion liquid tank 1. As the tube, a highly airtight tube such as a Tygon tube or a Teflon (registered trademark) tube is usually preferable. Further, the reaction vessel 3 is provided with a tube 7 such as a Tygon tube or a Teflon (registered trademark) tube for introducing the fluoride gas generated by the diffusion reaction between the sample and the diffusion liquid into the collection vessel 6. Yes. In order to improve the gas-liquid contact between the fluoride gas and the collection liquid, it is preferable to provide a sponge 8 or the like that has absorbed the collection liquid in the collection tank 6. The amount of the collection liquid and NaOH used here is preferably about 2 cc to 3 cc.

In the present invention, as shown in FIG. 1, two syringes 9 and 10 with variable volume are used. The volume of these two syringes is preferably the same, and usually 100 cc is preferred. As shown in FIG. 1, these syringes 9 and 10 are connected to the syringes 9 and 10, and further to the reaction tank 3 and the collection tank 6 by the same tube as described above, thereby forming a reaction system. ing. The reaction tank 3 is preferably provided with a cooling device 3a at the top. More specifically, the tubes coming out from the upper portions of the syringes 9 and 10 are divided into two forks and connected to the collection tank 6 and the reaction tank 3. A check valve is installed in the upper part of each tube exiting from the syringes 9 and 10, and the gas flow is set to flow only in the direction of the arrow in FIG. Also, a plunger holding base 11 and a spring 12 are respectively installed below the syringes 9 and 10, and the plunger 13 of the right syringe 9 and the plunger 14 of the left syringe 10 are the same in the opposite directions. It is preferable to set the automatic ventilation power so as to move by a distance.
Further, it is preferable to install a three-way valve L above the left syringe 10 and a three-way valve R above the right syringe 9. In addition, it is preferable to provide a three-way valve Y and a three-way valve Z on the tube connecting the collection tank 6 and the reaction tank 3 and a three-way valve X on the tube connecting the reaction tank 3 and the diffusion liquid tank 1.

Hereinafter, the procedure of the quantification method of the present invention will be described using the apparatus shown in FIG.
1) Introduction of sample First, a sample is placed in the reaction vessel 3. The amount of the sample can be any amount, but is usually about 1 to 40 g as a single dose. Thus, a considerably large amount of sample can be used in the present invention. Moreover, it is preferable to add the above-mentioned silicone antifoaming agent together with the sample.

2) Injection of diffusion liquid and adjustment of negative pressure in reaction system Next, an operation for adjusting the inside of the reaction system to negative pressure is performed while injecting the diffusion liquid. That is, first, the three-way valve L and the three-way valve R are operated so that the air in the left and right syringes 9 and 10 communicates with the outside air and does not move into the tube. Next, the automatic ventilation power is switched on, the plunger 14 of the left syringe 10 moves downward, and the plunger 13 of the right syringe 9 is switched off when it reaches the upper end. The three-way valve R is operated so that the air in the right syringe 9 does not communicate with the outside air, and the air in the tube and the right syringe 9 moves. On the other hand, preparation for pouring each diffusion liquid 2 in the diffusion liquid tank 1 into the reaction tank 3 is performed. That is, first, the diffusion liquid tank 1 is connected to the tube 5 via the three-way valve X, and the three-way valve X is operated so that only the tube 5 that connects the diffusion liquid tank 1 and the reaction tank 3 passes. Next, the automatic ventilation power is turned on, and the plunger 14 of the left syringe 10 moves upward, while the plunger 13 of the right syringe 9 moves downward. When the plunger 13 of the right syringe 9 reaches the bottom, the automatic ventilation power is switched off. By the above operation, the air in the left syringe 10, for example, 80 cc of air, is discharged to the outside. On the other hand, in the right syringe 9, for example, the volume increases by 80 cc. Negative pressure is generated. Soon, the diffusion liquid 2 in the diffusion liquid tank 1 is sucked into the reaction tank 3 and completely injected. At this stage, when the diffusion liquid prepared in the diffusion liquid tank 1 is, for example, 40 cc, the negative pressure corresponding to the volume of 40 cc is still maintained in the reaction system. Next, the three-way valve L is operated so that the air in the left syringe 10 does not communicate with the outside air, and the air in the tube and the left syringe 10 moves. Next, the three-way valve X is operated to close the passage leading from the diffusion liquid tank 1 to the tube 5 so that the gas flowing from the collection tank can be communicated into the reaction tank 3. Next, the diffusion liquid tank 1 is removed from the reaction system.
During the above process, the three-way valve Z is operated so that the gas from the collection tank 6 and the syringes 9 and 10 flows in the three-way valve X direction and does not flow directly in the three-way valve Y direction. The three-way valve Y is operated so that the flow from the three-way valve Z is closed and flows from the reaction tank 3 to the collection tank 6.
Thus, the injection of the diffusion liquid can be completed while the reaction system has a negative pressure lower than the external pressure.

3) Ventilation in the reaction system Next, by ventilating the reaction system, the fluoride gas generated by the diffusion reaction between the sample and the diffusion liquid in the reaction tank 3 is collected in the collection liquid in the collection tank 6. Like that. That is, first, the automatic ventilation power is switched on, and the plunger 14 of the left syringe 10 moves downward, while the plunger 13 of the right syringe 9 moves upward. At this time, the gas in the collection tank 6 moves into the reaction tank 3 via the tube 5, and further, the fluoride gas generated from the reaction tank 3 moves to the collection tank 6, and the gas in the reaction system Circulates in the system, and the fluoride gas generated by the diffusion reaction between the sample and the diffusion liquid in the reaction tank 3 is well collected in the collection liquid in the collection tank 6. When the fluoride gas moves from the reaction tank 3 to the collection tank 6, the water vapor is cooled in the cooling device 3a attached to the reaction tank and falls into the reaction tank and does not move in the three-way valve Y direction.
Then, after a certain period of time, the automatic ventilation power is switched off.
During the above-described steps, the three-way valve Z is operated so that the gas from the collection tank 6 and the syringes 9 and 10 flows in the three-way valve X direction and does not flow in the three-way valve Y direction. The three-way valve X is operated so that the flow to the diffusion liquid tank 1 is closed and flows from the three-way valve Z toward the tube 5. The three-way valve Y is operated so that the flow from the three-way valve Z is closed and flows from the reaction tank 3 to the collection tank 6.
Thus, the gas in the reaction system is ventilated, and the fluoride gas generated by the diffusion reaction is well collected in the collection liquid in the collection tank.

4) Ventilation of gas in the short circuit Next, the gas in the circuit in the reaction system is ventilated to collect the fluoride gas remaining in the reaction system in the collection liquid in the collection tank. That is, first, the three-way valve Z is operated so that the gas from the collection tank 6 does not flow in the direction of the three-way valve X, but flows only in the direction of the three-way valve Y. Further, the three-way valve Y is operated so that no gas flows in from the direction of the reaction tank 3, and only the flow from the three-way valve Z flows toward the collection tank 6. Next, the automatic ventilation power is turned on, and the plunger 14 of the left syringe 10 moves downward, while the plunger 13 of the right syringe 9 moves upward. At this time, the gas in the circuit circulates from the collection tank 6 to the three-way valve Z, the three-way valve Y, and then the collection tank 6, and is not collected in the tube or syringe other than the reaction tank 3. The remaining fluoride gas can be collected almost completely in the collection liquid in the collection tank.
During the above-described steps, operation is performed so that the flow from the three-way valve Z to the three-way valve Y does not flow to the three-way valve X and the reaction tank 3. Further, the three-way valve L is operated so as to flow from the syringe 10 to the upper tube without communicating with the outside air.
Thus, the fluoride gas remaining in the short circuit in the reaction system is collected in the collection liquid.

5) Collection and quantification of collected liquid Next, the fluoride in the sample is quantified by removing the collection tank from the apparatus and measuring the fluoride ion concentration in the collected liquid by the usual ion electrode method. Can do. Specifically, collect about 1 cc of sodium hydroxide solution in the collection tank, add about 0.1 cc of ion buffer TISAB III (ORION), and add fluoride ion (F) composite electrode ( Measure fluoride ion concentration using ORION 96-06). The fluoride concentration in the sample can be calculated by the following formula based on the sample weight and the collected liquid weight and by subtracting the blank value.

Fluoride concentration in sample =
(Fluoride ion concentration value in the collected liquid-blank value) x (weight of collected liquid / sample weight)

  In the steps 1) to 6) described above, for example, the steps 1) to 5) are performed for an arbitrary fixed time, the collected liquid in step 6) is collected, and then a new one is obtained. It is also possible to install a collection tank equipped with a collection liquid, perform step 2), step 4 and step 5), and perform quantitative determination of fluoride gas over time.

In the apparatus for quantitative determination of fluoride by ventilated micro-diffusion according to the present invention described above, it is preferable to use a reaction tank as shown in FIG. 2 as the reaction tank. The reaction tank shown in FIG. 2 is a central tube provided vertically from the diffusion liquid tank to the bottom of the reaction tank in order to introduce the diffusion liquid from the diffusion liquid tank into the reaction tank. 15 Furthermore, an intermediate cylinder 16 having a small hole 17 at the top is provided which covers the outside of the central tube in the vertical direction and extends to the bottom of the reaction tank longer than the central tube. Then, after the diffusion liquid from the diffusion liquid tank introduced from the central tube reaches the bottom of the central tube, it rises through the gap between the central tube and the intermediate cylinder covering the intermediate tube, It is designed so that the diffusion liquid is discharged from the small hole at the top of the cylinder to the reaction tank, and the diffusion liquid is circulated in the reaction tank through the central tube. More specifically, as shown in FIG. 2a, in the central tube, the ventilation air and the diffusion liquid from the diffusion liquid tank are drawn downward from above. As shown in b, between the central tube and the intermediate tube, the sample and the diffusion reaction liquid that are in the lower part are carried upward by the rising ventilation air and the diffusion liquid. As shown in c, the sample and the diffusion reaction solution are sucked from the bottom of the intermediate cylinder. As shown in d, the sample sucked from the lower part and the diffusion reaction liquid are discharged from the upper small hole of the intermediate cylinder. Next, as shown in e, outside the intermediate cylinder, the sample and the diffusion reaction liquid that were in the upper part are pulled downward.
By using such a reaction tank, the diffusion liquid can circulate well in the reaction tank without generating bubbles, and the diffusion reaction between the sample and the diffusion liquid in the reaction tank can proceed well. Become. In addition, in order to suppress the generation of foam, apply a silicone-based antifoaming agent inside the upper part of the reaction tank, or the sample and the diffusion solution may react with the silicone-based antifoaming agent at a constant concentration, for example, 100 ppm. It is preferable to mix in the case.

Specific examples of the central tube and the intermediate tube in the reaction tank are shown in FIGS. 3A shows an intermediate tube, B shows a central tube, and A + B in FIG. 3 shows a state in which these are combined. FIG. 4 more specifically shows the configuration of the intermediate cylinder A and the central tube B shown in FIG. Each component A1, A2 and A3 of the intermediate tube A shown in FIG. 4 and each component B1, B2, B3 and B4 of the central tube B are combined to form an intermediate tube and a central tube, respectively. By setting in the reaction tank as shown in 2, a target reaction tank can be obtained.
Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

Fluoride determination method by ventilated microdiffusion of the present invention and
Quantification of fluoride in sample using the apparatus (1) Apparatus Quantification was performed using the apparatus shown in FIG. This apparatus has two syringes 9 and 10 for ventilation, automatic ventilation power, reaction tank 3, diffusion liquid tank 1, collection tank 6 containing collected liquid, thermostatic water tank 4, and a tube connecting these and the flow of air It consists of three-way valves L, R, X, Z and Y that control
A commercially available 100 cc syringe (JMS) was used as the ventilation syringe. Automatic ventilation power moves the left and right syringes up and down at an arbitrary speed. When the right syringe moves from top to bottom, the switch automatically turns off when it reaches the bottom for the first time after switching on. However, when the right syringe moves upward from the bottom, the ventilation operation is continuously continued for an arbitrary time after the switch is turned on. In addition, it is possible to arbitrarily set a pause time from when the one-way movement is completed to when the movement is reversed and the movement is started. In this case, the one-way movement is 20 to 30 seconds, and the pause time is 2 to 3 seconds. In addition, when the syringe / plunger moves from the bottom to the top (to try to compress the air in the syringe), the spring attached to the holding table corresponds to the frictional resistance generated between the syringe inner surface and the plunger. It was devised so that the plunger moves slowly. Thereby, the negative pressure condition in the reaction system was always secured.

A commercially available 100 cc graduated cylinder was used as the reaction vessel. A device that circulates cold water was attached to the top to prevent water vapor from flowing out of the reaction vessel.
The diffusion tank was a 50 cc syringe (TERUMO) and a connection terminal was attached. As the diffusion solution, a 5.0 molar HClO ₄ solution saturated with HMDS was used.
The collection tank was a cylindrical part of a commercially available 25 cc syringe (JMS) and sealed with a rubber stopper. The collection solution was 0.1 to 0.01 molar NaOH. The sponge was used to soak up the collected liquid. What was formed in the column shape with the size which fits the form of a collection tank was used.
A Teflon (registered trademark) tube was used for the diffusion solution injection tube, a Tygon tube was used for the other connection, and a check valve and a three-way valve for controlling the gas flow were used.

(2) Work procedure The work procedure was as follows.
1. Sample and collection solution preparation:
40 cc of the sample was put into the reaction vessel and capped, and 0.01 to 0.1 molar NaOH and 2 to 3 cc were soaked in the sponge and set in the collection vessel.
2. Acid injection and negative pressure adjustment in reaction system:
The terminal of the diffusion liquid tank was connected to one valve of the three-way valve directly connected to the reaction tank, and the diffusion liquid was injected into the reaction tank. Here, the three-way valve connected to the left syringe was operated to discharge the exhaust to the outside, and the right syringe plunger was pulled with all the valves connected to the right syringe closed with the outside. A diffusion volume of 40 cc was prepared in the diffusion tank, while the volume change accompanying the movement of the syringe and plunger was 63 cc. Therefore, the one-way movement of the syringe accompanying the injection of the diffusion liquid adjusts the negative pressure by a volume of 40 cc with respect to the entire reaction system.

3. Diffusion reaction:
Ventilation in the reaction system and collection of fluoride gas: Set the state of each valve so that gas can flow throughout the reaction system, and again through the reaction tank, collection tank, and ventilation syringe. Gas was circulated. However, the short circuit was closed. A diffusion reaction was performed, and the ventilation operation time for collecting the generated fluoride gas was 1 hour and 1 hour 30 minutes.

4). Ventilation with short circuit:
After a certain time, the ventilation power switch was turned off. Therefore, two three-way valves connected to the reaction tank were operated to close the inlet / outlet of the reaction tank and make the short circuit pass. Ventilation operation was performed in this state, and fluoride gas remaining uncollected in the left and right syringes, in the collection tank, and in other connecting tubes was collected. As a result, the fluoride gas generated by the diffusion reaction in a certain time could be collected almost completely.
5). Collection and quantification of collected liquid:
After ventilating with the short circuit, the collection tank was removed. The sponge in the collection tank was repeatedly compressed and sucked with a plunger, and the collected liquid contained in the sponge, NaOH, was taken out while stirring uniformly. 1 cc of this NaOH was collected, 0.1 cc of TISAB III (ORION) 0.1 cc was added, and fluoride ion concentration was measured using an F composite electrode (ORION, 96-06). The blank value was subtracted from the measured value, and the final fluoride ion concentration in the sample was calculated based on the ratio between the sample amount and the collected liquid amount.

(3) Measurement experiment using 0.1 ppm F standard solution Diffusion temperature 50 ℃, plunger movement speed for ventilation 30 seconds one way, pause time 3 seconds, recovery time by short circuit 3 minutes, 0.1 ppm An F standard solution measurement experiment was performed.
Using 40 cc of a 0.1 ppm F standard solution as a sample, 40 cc of diffusion solution and 2 cc of collection solution were used. The diffusion time was 1 hour and the ventilation time by short circuit was 3 minutes. Measurements were performed 6 times under the same conditions.
(4) Measurement experiment using 0.01 ppm F standard solution Diffusion temperature 50 ° C, plunger movement speed for ventilation 30 seconds one way, pause time 3 seconds, recovery time by short circuit 3 minutes, 0.01 ppm An F standard solution measurement experiment was performed.
Using 0.01 cc F standard solution 40 cc as a sample, diffusion solution 40 cc and collection solution 2 cc were used. The diffusion time was 1 hour 30 minutes, and the ventilation time by the short circuit was 3 minutes. Measurements were performed 5 times under the same conditions.

(5) Results and discussion 1. Measurement experiment using 0.1 ppm F standard solution As shown in Table 1, the measurement results averaged 0.101 ppm and the CV value was 1.4%. While the theoretical value was 0.1 ppm, satisfactory results were obtained with a recovery rate of 101% and small fluctuations in measured values.

Table 1 Standard solution 0.1 ppm F recovery test
n F Measured value (ppm) SD (ppm) CV value (%)
6 0.101 0.001 1.4

2. Measurement experiment using 0.01 ppm F standard solution As shown in Table 2, the measurement result was an average of 0.0094 pm and a CV value of 4.1%. The theoretical value was 0.01 ppm, which was slightly inferior at 94% recovery. However, the variation in measured values was small. Measurement of this level of low fluoride concentration was considered to be satisfactory compared to previous reports.

Table 2 0.01 ppm F recovery test for standard solution
n F Measured value (ppm) SD (ppm) CV value (%)
5 0.0094 0.0004 4.1

From the results of these Examples, it was found that when the F standard solution was used, it could be measured with high accuracy even at F concentrations of 0.1 ppm and 0.01 ppm. Since the fluoride concentration in foods and drinks taken daily is about 0.1 ppm or higher, the device is considered highly useful for measuring fluoride concentration in foods. However, in order to cope with the recovery rate measurement at regular intervals, it is a future task to improve so that a more stable measurement value can be obtained at a low concentration of 0.01 ppm F level.
By automating the equipment, it became possible to measure the temperature, ventilation rate, diffusion time, and atmospheric pressure in the reaction system with strict standardization. Moreover, the syringe was only ventilated, and the reaction tank and the collection tank were easily managed by providing the reaction tank and the collection tank separately. Furthermore, even a part of the contents between the two tanks could not be mixed. As described above, strict comparison and examination of various conditions that affect the diffusion reaction and recovery rate, which was extremely difficult by manual operation, has become easier by automating the equipment.

As a reaction vessel, the reaction vessel shown in FIG. 2, more specifically, the reaction vessel comprising the components shown in FIG. 3 and FIG. The liquid was measured.
Specific measurement conditions are fluoride (F) standard solution volume 40cc, recovered solution (0.1 molar NaOH) 3cc, concentration factor 13.3 times, diffusion temperature 40 ° C, plunger movement speed for ventilation 20 seconds one way, The pause time was 2 seconds, the recovery time by the short circuit was 1 minute, and the diffusion time was 1 hour.
The obtained results are shown in Tables 3 to 5.

Table 3: 0.01 ppm F standard solution measurement
1st 0.0010 ppm
Second time 0.010 ppm
3rd 0.011 ppm
4th 0.012 ppm
5th 0.011 ppm
6th 0.011 ppm
Average value: 0.01 ppm
SD: 0.0008 ppm
CV value: 6.84%

Table 4: Measurement of 0.10 ppm F standard solution
1st 0.099 ppm
Second time 0.099 ppm
3rd 0.105 ppm
4th 0.108 ppm
5th 0.108 ppm
6th 0.108 ppm
Average value: 0.11 ppm
SD: 0.0044 ppm
CV value: 4.15%



Table 5: Measurement of 1.00 ppm F standard solution
1st 1.047 ppm
2nd 1.055 ppm
3rd 1.040 ppm
4th 1.040 ppm
5th 1.062 ppm
6th 1.070 ppm
7th 1.070 ppm
Average value: 1.05 ppm
SD: 0.0122 ppm
CV value: 1.16%

  As is apparent from the results shown in Tables 3 to 5, by using a reaction tank as shown in FIG. 2 as a reaction tank, even a low concentration of 0.01 ppm F level can be measured with satisfactory accuracy. It was. The reproducibility of measured data at 0.10 ppm F and 1.00 ppm F concentration levels was extremely high, with CV values of about 4% and about 1%, respectively.

The fluoride quantification method and apparatus by the ventilated microdiffusion of the present invention described above has the following advantages.
1) Since the internal pressure of the reaction system is adjusted to a negative pressure to perform quantification, the internal pressure of the reaction system does not exceed 1 atm. Therefore, a reaction gas such as fluoride gas does not leak from the reaction system to the outside.
2) The reaction rate can be controlled by adjusting the temperature of the reaction tank (depending on the temperature of the constant temperature water tank), the concentration of the diffusion liquid, and the ventilation rate.
3) Since the reaction tank and the collection tank are separate, the reaction liquid of the sample and the diffusion liquid, specifically, the sample and HClO ₄ do not mix with the collection liquid.
4) In the present invention, two syringes with variable volume are used, and it is not necessary to replace these syringes during quantification, so that work efficiency can be improved.
5) For example, when the volume of the reaction vessel is 100 cc, for example, a 40 g (40 cc) sample can be used in the reaction vessel. If a sample of 40 g is used and the collected liquid is 2 cc (2 g), for example, the concentration will be 20 times. In addition, measurement samples can be added as required, and the concentration can be arbitrarily concentrated even if the fluoride concentration of the collected liquid is 20 times or more.
6) Even with a low-concentration fluoride sample, if the amount of sample used for measurement is increased, it can be measured within the measurable level of the F composite electrode, and reliable data can be obtained.
7) After the diffusion reaction is started, a new time can be measured for the diffusion reaction by changing a new collection tank every certain time.
8) From the data following the diffusion time for each sample, grasp the aging pattern of the diffusivity, and when the diffusivity becomes zero, the end point of the diffusion reaction is taken, and from the value obtained here, the food is more accurate. Fluoride content and concentration of can be calculated. In the existing method, since it is a batch process, the end point of the diffusion reaction could not be obtained.
9) By using a reaction tank as shown in FIG. 2 as the reaction tank, the diffusion liquid can be circulated well in the reaction tank, and therefore the diffusion reaction can proceed well. It is possible to accurately quantify foods that are liable to foam by contact with the air or by stirring by ventilation, or foods that tend to form lumps.

The apparatus used for the fluoride determination by ventilation type microdiffusion of this invention is shown. 1 is a diffusion liquid tank, 2 is a diffusion liquid, 3 is a reaction tank, 3a is a cooling device attached to the reaction tank, 4 is a constant temperature water tank, 5 and 7 are tubes, 6 is a collection tank, 8 is a sponge, 9 is a right side 10 is a left side variable volume syringe, 11 is a plunger holder, 12 is a spring, 13 is a plunger of a right syringe, 14 is a plunger of a left syringe, L, R, X, Z and Y indicate a three-way valve L, a three-way valve R, a three-way valve X, a three-way valve Z, and a three-way valve Y, respectively. The preferable reaction tank in the apparatus used for the fluoride determination by the ventilation type microdiffusion of this invention is shown. Reference numeral 15 denotes a central tube for introducing the diffusion liquid from the diffusion liquid tank into the reaction tank, 16 denotes an intermediate cylinder, and 17 denotes a small hole provided in the upper part of the intermediate cylinder. The specific example of the center tube and intermediate | middle cylinder which are shown in FIG. 2 is shown. A is an intermediate tube, B is a center tube, and A + B is a combination of these. The configuration of the intermediate cylinder A and the central tube B shown in FIG. 3 will be described more specifically. A1, A2 and A3 are each component of the intermediate tube of A, and B1, B2, B3 and B4 are each component of the central tube of B.

Claims (11)

Diffusion reaction of strong acid on the sample is diffused, the resulting fluoride is adsorbed on the collected liquid and collected, and the fluoride ion concentration in the collected liquid is measured to quantify the fluoride in the sample. In the fluoride determination method by the formula microdiffusion,
The reaction system consists of two variable volume syringes, a reaction tank, and a collection tank containing the collection liquid. These are connected by a tube, and the reaction system is adjusted to a negative pressure by operating the two variable volume syringes. And collecting the fluoride gas produced by the diffusion reaction between the sample and the diffusion liquid in the reaction tank by ventilating the gas in the reaction system including the reaction tank and the collection tank. To be adsorbed to the collected liquid,
Quantitative determination of fluoride by ventilated micro-diffusion.   After putting the sample in the reaction tank and then operating the two variable volume syringes to adjust the inside of the reaction system to negative pressure, the diffusion liquid tank containing the diffusion liquid is connected to the reaction tank containing the sample, and the volume The method for quantifying fluoride according to claim 1, wherein the two variable syringes are operated to inject the diffusion liquid into the reaction vessel.   In the reaction tank, the diffusion liquid and the sample undergo a diffusion reaction, and the fluoride gas produced is activated by operating two volume-variable syringes to ventilate the gas in the reaction tank and the collection tank. The method for quantitative determination of fluoride according to claim 1 or 2, which is introduced into.   The two variable volume syringes are operated to ventilate the gas in the reaction system, thereby collecting the fluoride gas remaining in the reaction system in the collection liquid in the collection tank. Either fluoride determination method.   The fluoride determination method according to any one of claims 1 to 4, wherein perchloric acid is used as a strong acid, and a sodium hydroxide solution is used as a collecting liquid.   The fluoride quantification method according to any one of claims 1 to 5, wherein the collection liquid in the collection tank is used by being adsorbed to a sponge provided in the collection tank.   The fluoride according to any one of claims 1 to 6, wherein a silicone-based antifoaming agent is applied to the inside of the upper part of the reaction vessel, or a silicone-based antifoaming agent is mixed during a diffusion reaction between the sample and the diffusion liquid in the reaction vessel. Quantitative method. Diffusion reaction of strong acid on the sample is diffused, the resulting fluoride is adsorbed on the collected liquid and collected, and the fluoride ion concentration in the collected liquid is measured to quantify the fluoride in the sample. In the apparatus for the determination of fluoride by the formula microdiffusion,
It consists of two variable volume syringes, a reaction tank and a collection tank, which are connected by a tube to form a reaction system, and the reaction system is adjusted to a negative pressure by operating the two variable volume syringes, and the reaction The gas in the reaction system including the tank and the collection tank can be ventilated, and the fluoride gas generated by the diffusion reaction between the sample and the diffusion liquid in the reaction tank can be introduced into the collection tank. Being
A device for the determination of fluoride by ventilated microdiffusion, characterized in that.   The apparatus according to claim 8, further comprising a diffusion liquid tank for introducing the diffusion liquid into the reaction tank.   A central tube vertically extending from the diffusion liquid tank to the bottom of the reaction tank to introduce the diffusion liquid from the diffusion liquid tank into the reaction tank as a reaction tank; A reaction vessel that covers the outside of the tube in the vertical direction and extends to the bottom of the reaction vessel longer than the central tube and is provided with an intermediate cylinder having a small hole at the top, and is a diffusion liquid introduced from the central tube After the diffusion liquid from the tank reaches the bottom of the central tube, it rises through the gap between the central tube and the intermediate cylinder covering it, and diffuses from the small hole at the top of the intermediate cylinder to the reaction tank. The apparatus according to claim 8 or 9, wherein a reaction tank designed to discharge liquid and circulate the diffusion liquid in the reaction tank through the central tube is used. The apparatus in any one of Claims 8-10 which apply | coated the silicone type antifoamer inside the upper part of the reaction tank.

Images