JP2001153828A - Method and device for measuring organic carbon content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for measuring organic content for monitoring carbon contents at a real time substantially without requiring any strict flow rate regulation. SOLUTION: This measurement device is provided with an oxidation container 10 allowing passage of a sample liquid, an ultraviolet light source 20 radiating ultraviolet light to the sample liquid inside the oxidation container 10, a lighting controlling means 21 turning off the ultraviolet light source 20 after turning it on for a fixed time, a conductivity detecting electrode 30 arranged in the vicinity of an outlet of the oxidation container 10, and a computing device 40 computing organic carbon contents in the sample solution from a difference between the base conductivity before turning on the ultraviolet light and the maximum conductivity after turning off the light. When a flow rate of the sample liquid passing through the oxidation container 10 is represented by F and an internal volume within an ultraviolet radiation range of the oxidation container 1 on the upstream side beyond the conductivity detecting electrode 30 is represented by V, the flow rate F is controlled so that a relationship F<=V/T is established between the flow rate F, the internal volume V, and a ultraviolet radiation time T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic carbon content measuring method and apparatus for measuring the total organic carbon content (TOC) of ultrapure water and the like, and more particularly, to a sample liquid such as ultrapure water. The present invention relates to an apparatus and method for measuring the content of organic carbon in a sample solution by irradiating the sample solution with ultraviolet rays and measuring the conductivity of the sample solution which is changed by an organic acid or carbon dioxide generated.

[0002]

2. Description of the Related Art In modern advanced industrial manufacturing processes and the like, highly purified "ultrapure water" is often used in large quantities. For example, in the cleaning of semiconductors, the production of medical chemicals and injections, the chemical analysis, and the like, pure water substantially free of impurities such as fine particles, various ions, microorganisms such as bacteria, and dissolved substances such as organic compounds and the like is used. Indispensable. A system for producing such pure water generally uses a combination of various filtration means including a reverse osmosis method, a distillation method, an ion exchange method, an adsorption method, a vacuum degassing method, an ultraviolet oxidation method, and an ultrafiltration method. In particular, for example, in the semiconductor manufacturing field, L
As the degree of integration of SI increases, the spacing between circuits becomes narrower, so it is necessary to further purify semiconductor cleaning water to prevent short circuits. Not only ions but also fine particles, bacteria, and organic substances are possible. It must be removed as much as possible.

[0003] As one of methods for expressing the cleanliness of pure water, total organic carbon (TO), which indicates the degree of pollution by the amount of carbon in organic matter in water,
C) There is a value. As a means of measuring the TOC value of pure water,
Ultraviolet (UV) oxidation TOC meters are widely used. In such a TOC meter, a sample liquid is introduced into an ultraviolet irradiation unit, where the sample liquid is irradiated with ultraviolet light to convert organic carbon in the sample liquid into organic acids and carbon dioxide. Then, based on the change in conductivity of the sample liquid obtained thereby, the T
The OC value is determined.

[0004] As the TOC meter of the ultraviolet oxidation system, various types are used.
An apparatus disclosed in Japanese Patent Publication No. 3-46375 is known. In this method, an ultrapure water sample stopped in a sample cell is irradiated with ultraviolet rays, and a change in conductivity during this time is measured by a conductivity detection electrode arranged in the sample cell. Then, after confirming that the oxidation reaction by the ultraviolet ray is substantially completed by the rate of change in conductivity, the organic carbon content is determined from the change in conductivity up to that time.

[0005] Also, before and after the ultraviolet irradiation section, the first and second ultraviolet rays are irradiated.
A measurement line having a conductivity sensor is provided, and ultrapure water is continuously flowed through the measurement line at a constant flow rate, and the organic carbon content is measured based on the difference between the conductivity obtained by the first and second conductivity sensors. Devices are also known. This apparatus is based on the premise that if the flow rate of ultrapure water flowing through the ultraviolet irradiation unit is constant, the amount of ultraviolet light received by the ultrapure water per unit volume is constant, that is, the degree of progress of the oxidation reaction is constant. . In this case, since the measurement can be performed while the oxidation reaction by the ultraviolet ray is not completed, the organic carbon content can be continuously measured.

[0006]

SUMMARY OF THE INVENTION Among the above conventional devices,
The former type of apparatus that determines the organic carbon content from the change in conductivity until the oxidation reaction by ultraviolet light is substantially completed has the following problems. First, the time required for completing the oxidation reaction is about 10 to 20 minutes, depending on the components of the sample solution and the intensity of ultraviolet light. Therefore, it is difficult to monitor the sample liquid in real time.

Further, since the sample liquid is kept stationary in the sample cell until the oxidation reaction is completed, the elution from the material constituting the sample cell and the conductivity detecting electrode mixes with the sample liquid to increase the conductivity. Let it. On the other hand, the generated carbon dioxide may leak to lower the conductivity. Therefore, the measured values must be corrected in consideration of these changes in conductivity that do not depend on the organic carbon content.

Further, in order to determine the progress of the oxidation reaction based on the change in conductivity, the conductivity detecting electrode must be disposed in the sample cell. As a result, the structure of the sample cell becomes complicated, making it difficult to produce the sample cell.

On the other hand, among the above-mentioned conventional apparatuses, the latter apparatus which continuously flows ultrapure water at a constant flow rate and continuously measures the organic carbon content from the difference in conductivity before and after irradiation with ultraviolet light has the following problems. There was a point. First, as described above, what can be measured without completing the oxidation reaction is that if the flow rate of ultrapure water flowing through the ultraviolet irradiation unit is constant, the amount of ultraviolet light received by the ultrapure water per unit volume is constant. It is premised on that. If the flow rate of the ultrapure water passing through the ultraviolet irradiation unit increases, the amount of ultraviolet irradiation per unit volume of the ultrapure water decreases, so that the difference in conductivity decreases. In addition, if the flow rate decreases, the amount of ultraviolet irradiation per unit volume of ultrapure water increases, so that the difference in conductivity increases. That is, when the flow rate of the ultrapure water passing through the ultraviolet irradiation unit changes, a measurement error occurs immediately. In order to avoid such errors, it is necessary to control the flow rate of ultrapure water very strictly. Therefore, the liquid feeding system is complicated, and the cost of the entire apparatus is easily increased. further,
To see the difference in conductivity before and after UV irradiation, the first and second
Are required, and a circuit for processing signals from these sensors is required. Therefore, from this aspect as well, the apparatus is likely to be complicated and costly.

The present invention has been made in view of the above circumstances, and enables a method of measuring an organic carbon content that does not require strict flow control, while enabling monitoring of the organic carbon content substantially in real time. It is an object to provide a device.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor studied to control the irradiation amount of ultraviolet light to the flowing sample liquid by the lighting time of the ultraviolet light source. As a result, if the sample liquid is allowed to pass through the oxidation vessel at a certain flow rate or less, the sample liquid portion where all the ultraviolet rays from the start of turning on the ultraviolet light source to the turning off can be present. The inventor has conceived that the amount of ultraviolet irradiation of the sample liquid portion depends on the lighting time of the ultraviolet light source.

That is, in order to solve the above-mentioned problems, the present invention allows a sample solution to pass through an oxidation container, irradiates the sample solution with ultraviolet rays for a certain period of time, and stops the irradiation. The base conductivity and the maximum conductivity after the irradiation were stopped were measured at a conductivity detection electrode provided near the outlet of the oxidation vessel, and the difference between the base conductivity and the maximum conductivity was used to determine the content of organic carbon in the sample solution. The flow rate of the sample solution passing through the inside of the oxidation vessel, and the internal volume V of the oxidation vessel on the upstream side of the conductivity detection electrode where the ultraviolet ray is irradiated.
And an irradiation time T of ultraviolet rays has a relation of F ≦ V / T.

[0013] In this specification, "the vicinity of the outlet of the oxidation vessel" where the conductivity detecting electrode is disposed is defined as the inside of the oxidation vessel upstream of the outlet of the oxidation vessel and the outside of the oxidation vessel downstream of the oxidation vessel. It is a concept that includes both. In addition, in the case of the inside of the oxidation container, there are possibilities both within the range irradiated with ultraviolet rays and outside the range irradiated with ultraviolet rays.

In this specification, the term “ultraviolet light irradiation time T” refers to not only the time during which complete continuous irradiation is continued, but also a light source (for example, a xenon flash lamp) that blinks at a constant frequency. This is a concept that includes the time during which the irradiation is continued. That is, individual blinking within the irradiation time T does not correspond to irradiation and stop of irradiation or lighting and extinguishing.

According to the present invention, there is a sample liquid portion to which all the ultraviolet rays from the start of turning on the ultraviolet light source to the extinguishing of the ultraviolet light source are present, and this shows the maximum conductivity based on the oxidation reaction according to the ultraviolet irradiation time. The organic carbon content can be determined without depending on the flow rate fluctuation.

[0016] After the maximum conductivity is measured, it is preferable that the flow rate of the sample solution passing through the oxidation vessel is increased to replace the sample solution in the oxidation vessel. Thus, the sample solution containing the oxidation product remaining in the oxidation container or the like can be discharged in a short time, so that the time until the next measurement can be shortened. Further, even if air bubbles are generated in the oxidation container, the conductivity detection electrode, or the like, when the flow rate is increased, the air bubbles can be poured out and removed.

It is desirable to use a photocatalyst in order to promote ultraviolet oxidation of organic carbon in the sample solution. As a result, even with the same ultraviolet irradiation time, a larger change in conductivity can be obtained, so that the detection sensitivity can be improved.

Further, the amount of ultraviolet light may be measured, and an alarm may be output when the measured amount of light becomes smaller than a predetermined value. Thereby, the user can be notified of the deterioration of the light source and the like.

The present invention also provides an oxidizing container through which a sample solution passes, an ultraviolet light source for irradiating the sample solution in the oxidizing container with ultraviolet light, lighting control means for turning on the ultraviolet light source for a predetermined time, and then turning off the light. The conductivity detection electrode provided in the vicinity of the outlet of the oxidation container, and the difference between the base conductivity before the start of lighting of the ultraviolet light measured by the conductivity detection electrode and the maximum conductivity after the light is turned off in the sample solution. A calculation device for calculating the organic carbon content, the flow rate F of the sample solution passing through the inside of the oxidation vessel, and the internal volume V of the oxidation vessel on the upstream side of the conductivity detection electrode where the ultraviolet rays of the oxidation vessel are irradiated. And a flow rate control means for controlling the flow rate F such that the irradiation time T of the ultraviolet ray satisfies the relation of F ≦ V / T.

According to the present invention, it is possible to allow the sample liquid portion to be entirely irradiated with the ultraviolet rays from the start of turning on the ultraviolet light source to the turning off of the ultraviolet light source. Since the maximum electric conductivity based on the flow rate can be obtained, the organic carbon content can be obtained without depending on the flow rate fluctuation.

As described above, after the maximum conductivity is measured, it is desirable to increase the flow rate of the sample solution passing through the oxidation container to replace the sample solution in the oxidation container. Further, in order to promote ultraviolet oxidation of organic carbon in the sample solution, it is desirable to provide a photocatalyst in the oxidation container.

In a case where a photocatalyst is provided in the oxidation container, a desirable configuration is such that the oxidation container has a double tube structure in which a sample liquid passes between an outer cylinder and an inner cylinder made of a material substantially transmitting ultraviolet rays. Provided is a configuration in which a photocatalyst is coated on an inner side of an outer cylinder and an ultraviolet light source is disposed on an inner cylinder side. In this case, the ultraviolet light source may be housed inside the inner tube, or the outer tube of the ultraviolet light source may also serve as the inner tube of the oxidation container.

It is desirable that the apparatus of the present invention includes a light meter for measuring the amount of ultraviolet light from the ultraviolet light source. Thus, when the light amount measured by the light meter becomes equal to or less than a certain value, an alarm is output or the like, so that the user can be notified of the time to replace the ultraviolet light source. It is also conceivable to correct the organic carbon content in consideration of the fluctuation or decrease in the amount of ultraviolet light.

Further, it is desirable that the apparatus of the present invention has a means for confirming the flow rate F at which the sample solution passes through the inside of the oxidation vessel. Thus, the flow rate F, the inner volume V of the oxidation container in the range upstream of the conductivity detection electrode where the ultraviolet rays are irradiated, and the irradiation time T of the ultraviolet rays may be in a relationship of F ≦ V / T for some reason. When it becomes impossible to keep the alarm, it is possible to output an alarm or the like.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment of the organic carbon content measuring device according to the present invention. In the oxidation container 1 through which the sample solution passes, there is an ultraviolet irradiation area 2 (shaded area) where ultraviolet light from an ultraviolet light source (not shown) is irradiated for a predetermined time T.
Further, a conductivity detection electrode 3 is disposed in the ultraviolet irradiation region 2 slightly upstream of the outlet 1 a of the oxidation container 1. The flow rate F of the sample solution flowing from the inlet pipe 4 to the outlet pipe 5 via the oxidation vessel 1 is determined by the internal volume V of the ultraviolet irradiation area 2 on the upstream side of the conductivity detection electrode 3 and the irradiation time T of the ultraviolet light.
The flow rate can be controlled by flow rate control means (not shown) so as to satisfy the relationship of ≤V / T.

The form of the oxidation vessel 1 and the ultraviolet light source is not particularly limited, but a form in which irradiation is performed from the inner tube side of a double-pipe oxidation vessel, as will be described in detail in Examples described later, can be suitably used. In addition, various modes such as a mode in which an ultraviolet light source is arranged outside the side surface of a tubular oxidation container and a mode in which a tube wound in a spiral shape around the outside of a cylindrical ultraviolet light source is used as an oxidation container can be appropriately adopted. In addition, a mercury lamp can be suitably used as the ultraviolet light source, but is not particularly limited thereto, and a xenon flash lamp, an ultraviolet lamp using silent discharge, or the like can be used.

A photocatalyst for promoting ultraviolet oxidation of organic carbon is provided in the oxidation container. As the photocatalyst, titanium oxide (TiO ₂ ) can be most preferably used, but other than that, SrTiO ₃ , CDS, WO ₃ ,
Fe ₂ O ₃ , MO _{3 and the} like can be given. In order to provide the photocatalyst in the oxidation container, the catalyst may be filled in the container as it is, or the inner wall of the oxidation container, beads or the like filled in the oxidation container may be coated.

As the flow control means, it is needless to say that a pump capable of maintaining a constant flow rate can be employed, but it is also necessary to control the supply pressure of the sample liquid or to apply a back pressure to the outlet 5 side. A pressure regulating valve, an orifice, or the like may be employed as the flow control means. In addition, the flow rate control means may be configured such that F ≦ V / T
In addition to maintaining the relationship, the flow rate can be switched to a larger value. Specifically, such a function can be achieved by a valve that opens when a large flow rate is set, a switching valve that switches between two flow paths with pumps having different flow rates, a pump that changes the flow rate, and the like.

FIG. 2 shows another embodiment of the organic carbon content measuring apparatus according to the present invention. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the conductivity detection electrode 3 is located slightly upstream of the outlet 1 a of the oxidation container 1 and downstream of the ultraviolet irradiation region 2.
Is arranged. The flow rate F can be controlled by a flow rate control means (not shown) so that the relation of F ≦ V / T with the inner volume V of the ultraviolet irradiation region 2 and the irradiation time T of the ultraviolet light is satisfied. Note that the internal volume of the sample solution that has passed through the ultraviolet irradiation region 2 until it reaches the conductivity detection electrode 3 is Va.
It is.

FIG. 3 shows still another embodiment of the organic carbon content measuring device according to the present invention. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the conductivity detection electrode 3 is disposed slightly downstream of the outlet 1a of the oxidation container 1. The flow rate F can be controlled by a flow rate control means (not shown) so that the relation of F ≦ V / T with the inner volume V of the ultraviolet irradiation region 2 and the irradiation time T of the ultraviolet light is satisfied. In addition,
The sample liquid that has passed through the ultraviolet irradiation area 2 is used as the conductivity detection electrode 3
Is Vb.

When the apparatus shown in FIG. 1 is operated at a constant flow rate F, the relationship between the conductivity C detected by the conductivity detection electrode 3 and the time t after the start of lighting is determined by the flow rate F shown in FIG. (A)
To (c).

First, (a) shows a change in conductivity when F = V / T. In this case, the sample liquid portion at the entrance of the ultraviolet irradiation area at the start of lighting reaches the position of the conductivity detecting electrode 3 just at the time of turning off (t = T). Also,
The sample liquid portion located at the entrance of the ultraviolet irradiation area when the light is turned off reaches the position of the conductivity detection electrode 3 at t = 2T. That is, at the position of the conductivity detection electrode 3,
At t = T, the sample liquid portion irradiated with ultraviolet light for the longest time (T) arrives, and at t = 2T, the same sample liquid portion not irradiated with ultraviolet light as at t = 0 arrives. When t is 0 to T, the portion of the sample liquid which has been oxidized by ultraviolet light during the time t arrives at the position of the conductivity detection electrode 3, and when t is T to 2T, the position of the conductivity detection electrode 3 is changed. In
During the time (2T-t), the sample liquid portion oxidized by the ultraviolet ray arrives. The conductivity C is so increased As the progresses ultraviolet oxidation, comprising a change that takes the maximum value C ₁ corresponding to the organic carbon content in t = T, as shown in figure shown so.

Next, (b) shows the change in conductivity when F <V / T. In this case, when the light is turned off (t = T), the portion of the sample liquid that has already flowed into the ultraviolet irradiation area 2 at the start of lighting reaches the position of the conductivity detection electrode 3. Then, the sample liquid portion at the entrance of the ultraviolet irradiation area at the start of lighting is t = t ₁ after the turning off (t = T).
At the position of the conductivity detection electrode 3. In addition, the sample liquid portion at the entrance of the ultraviolet irradiation area at the time of turning off just reaches the position of the conductivity detection electrode 3 at t = t ₂ (= t ₁ + T). That, t is the position of Mashirube conductivity sensing electrode 3 of T~t _1, and the longest time arrive continuously during UV oxidized sample liquid portion (T), t = t
_{At 2} , the sample liquid portion that has not been irradiated with the same ultraviolet rays as at t = 0 arrives. In addition, while t is 0 to T,
The position conductivity detecting electrode 3 reaches the ultraviolet oxidized sample liquid portion during the time t, while t is t ₁ ~t _2, the position of the conductivity sensing electrode 3, the time (t ₂ - During the period t), the sample liquid portion which has been oxidized by ultraviolet rays reaches. Therefore, the conductivity C
As shown in the figure, consisting of variations t continues the maximum value C ₁ between T～t ₁ to indicate so.

On the other hand, (c) shows that F> V /
The change in conductivity in the case of T is shown. In this case, the sample liquid portion was at the entrance of the ultraviolet irradiation area at the lighting start, reaches the position of the light-off (t = T) Conductivity sensing electrode 3 in the previous t = t _3. At the time of turning off the light (t = T), the portion of the sample liquid that has reached the position of the conductivity detection electrode 3 at the start of the lighting is still the sample liquid portion that is still upstream of the ultraviolet irradiation region 2. Further, the sample liquid portion at the entrance of the ultraviolet irradiation area at the time of turning off reaches the position of the conductivity detection electrode 3 at t = t ₄ (= t ₃ + T). That is, t
There the location of Mashirube conductivity sensing electrode 3 t ₃ through T, a short time only ultraviolet oxidized sample liquid portion than T arrives continuously. Incidentally, while t is 0 to t _3, the position of the conductivity sensing electrode 3 reaches the ultraviolet oxidized sample liquid portion during the time t, while t is T～t _4, the conductivity sensing electrode 3 The sample liquid portion oxidized by ultraviolet rays during the time (t ₄ -t) arrives at the position of ( ₄ ). Therefore, as shown in FIG.
t is show change to continue the maximum value _{C 2} between _t 3 through T,
C ₂ is smaller than the _{C 1.} Incidentally, C ₂ becomes smaller as increases F Gayori.

That is, the flow rate F shown in (a) or (b)
Under the condition (F ≦ V / T), the maximum value C ₁ of the conductivity is obtained, and even if the flow rate F changes, only the duration of taking the value of C ₁ changes. Therefore, even when the flow rate varies, the maximum conductivity C ₁ based on the same oxidation conditions and the base conductivity C
A difference from ₀ is obtained, and from this value, the content of organic carbon in the sample liquid can be determined.

Next, when the apparatus shown in FIGS. 2 and 3 is operated at a constant flow rate F, the relationship between the conductivity C detected by the conductivity detection electrode 3 and the time t after the start of lighting is shown. It is shown in FIG. In FIG. 5, as in FIG. 4, (a) shows that F = V /
(B) shows the conductivity change when F <V / T, and (c) shows the conductivity change when F <V / T.

[0037] In (a) ~ (c) any of the conditions as shown in FIG. 5, time duration t ₅ is the time the sample liquid is moved from the exit of the UV irradiation region 2 until the conductivity sensing electrode,
A response delayed from the corresponding (a) to (c) of FIG. 4 is obtained. In the case of the device of FIG. 2, t ₅ = Va / F, and in the case of the device of FIG. 3, t ₅ = Vb / F. That is, in order to obtain the data of the maximum conductivity C ₁ earlier to reduce the t ₅ is, Va, it is desirable to fabricate the device as small as possible to Vb.

[0038] Figures 4 and 5 has been described the flow rate F for explaining a constant, preferably, after obtaining the maximum conductivity C ₁ is the F to the large flow rate, the sample liquid replacement and bubbles Discharge. Thus, conductivity C is quickly and then returned to the base conductivity C _0, it can be started early next measurement.

The switching to the large flow rate, after lighting start, to predict the time until it can be determined that the maximum conductivity C ₁ can be surely obtained, may be switched in time uniformly. In order to return to the base conductivity C ₀ earlier, the maximum conductivity C ₁
It is good to detect that it was obtained, and to switch immediately at that time. To detect that the conductivity has reached a maximum,
Change in conductivity C (differential value) as usual
Can be considered to confirm that the value has become equal to or less than a predetermined value. Moreover, by utilizing the fact that the temperature of the sample solution fluctuates slightly due to heat generation of the ultraviolet light source, with the temperature becomes the maximum value, it may be determined that when the resulting maximum conductivity C _1.

As described above, when the maximum conductivity is detected by the conductivity or the temperature, the approximate value of the flow rate F is known from the time until it is detected.
/ T (in the case of the embodiment of FIG. 1, FIG.
In the case where the conductivity becomes maximum in a shorter time than T as shown in (c)), a response such as an alarm output can be taken. In addition, it is a matter of course that a flow meter may be separately prepared as a means for checking the flow rate F.

When comparing the embodiment of FIGS. 1 to 3, as shown in FIG.
Since the specific structure of the conductivity detection electrode 3 is not limited by the specific structure of the oxidation container 1, the manufacturing method is generally easy. However, it is easier to shorten the time until the maximum conductivity is obtained by adopting the embodiment of FIG. 2 than FIG. 3 and FIG. 2 than FIG. In addition, in the case of adopting the embodiment shown in FIG. 1, since the conductivity detection electrode 3 is also irradiated with ultraviolet rays, there is an advantage that dirt which hinders the conductivity detection is hardly attached.

[0042]

FIG. 6 shows an embodiment of the present invention. The organic carbon content measuring device shown in FIG.
UV light source 20 for irradiating the sample liquid in 0 with ultraviolet light from inside
Lighting control means 21 for turning on and off the ultraviolet light source 20 for a certain period of time; a photodiode 22 as a light meter for measuring the light amount of the ultraviolet light source 20;
And an arithmetic unit 40 to which data from the conductivity detection electrode 30 and data of the photodiode 22 are input.
And

Further, the present apparatus is provided with a flow control means comprising a pressure regulating valve 51, an orifice 52, and a normally closed valve 53. The pressure adjusting valve 51 adjusts so that the sample solution having a certain pressure or more is released to the drainage side, and the sample solution is supplied at a certain range of pressure to the inlet pipe of the oxidation vessel 10 branched at the upstream side. is there. The orifice 52 is provided with the conductivity detecting electrode 3.
The flow rate F of the sample liquid and the inner volume V of the ultraviolet irradiation area in the oxidation vessel 10 are provided by the back pressure and the supply pressure adjustment by the pressure adjustment valve 51 provided at the drain side flow path downstream of the O. And the irradiation time T of the ultraviolet light are adjusted to satisfy the relationship of F ≦ V / T. The normally closed valve 53 is provided in a flow path through which the sample liquid from the conductivity detection electrode 30 can be drained in parallel with the flow path in which the orifice 51 is provided. To open and close. When the normally closed valve 53 is opened, a flow rate F considerably larger than V / T is obtained.

A specific example of the structure of the oxidation container 10 will be described with reference to FIG. The oxidation container 10 of FIG. 7 has an outer cylinder 11 and an inner cylinder 12, and forms a double-pipe structure with a ring-shaped lower bottom 13 and an upper bottom 14 connecting both ends thereof. Further, an inlet pipe 15 and an outlet pipe 16 for flowing the sample liquid into and out of the space are provided. The inner wall surface of the outer cylinder 11 is coated with titanium oxide. The inner tube 12 is formed of a material that allows ultraviolet rays to pass, such as quartz glass, and is not coated with titanium oxide or the like. In FIG. 7, the ultraviolet light source 20 is inserted inside the inner cylinder 12 of the oxidation container 10, and the sample liquid passing through the irradiation region 23 to which the ultraviolet light from the ultraviolet light source 20 reaches is oxidized by the ultraviolet light. I have.

Another specific example of the oxidation container 10 will be described with reference to FIG. The oxidation container 10 of FIG. 8 has an outer cylinder 11 and a ring-shaped lower bottom 13 and an upper bottom 14 at both ends. Further, the ultraviolet light source 20 includes the lower bottom 13 and the upper bottom 1 of the oxidation container 10.
The outer tube of the ultraviolet light source 20 doubles as the inner tube of the oxidation container 10 by being inserted through the inside of the outer tube 11 in a water-tight manner using a packing 17 between the outer tube 4 and the outer tube 4. And outer cylinder 1
1, the lower bottom 13 and the upper bottom 14 together form a space of a double tube structure, into which the sample liquid flows in from the inlet tube 15 and flows out from the outlet tube 16. The inner wall surface of the outer cylinder 11 is coated with titanium oxide. Also in this case, the irradiation area 2 to which the ultraviolet light from the ultraviolet
The sample liquid passing through 3 is oxidized by ultraviolet rays.

In the oxidation container 10 shown in FIG. 7 or FIG. 8, the ultraviolet rays reach the outer cylinder coated with titanium oxide without being substantially blocked, and the oxidation reaction of the sample liquid in contact therewith. Can proceed efficiently. In addition, it was confirmed that when the outer cylinder was coated with titanium oxide, ultraviolet rays hardly leaked from the outer cylinder to the outside. That is, almost all the energy of the ultraviolet rays is consumed for the oxidation reaction without leaking to the outside. Also,
Ultraviolet rays do not leak to the outside and do not damage peripheral devices or adversely affect workers. Further, the ultraviolet light source 20
Is inserted into the inside of the oxidation container 10, and the outside of the container is surrounded by a liquid layer composed of the sample liquid. Therefore, the temperature change of the ultraviolet light source can be suppressed small, and the stability of the ultraviolet light source can be improved.

The operation of the organic carbon content measuring device shown in FIG. 6 will be described with reference to FIG. First, the normally closed valve 53 is turned off and closed, and the sample solution is flown into the oxidation container 10 at a flow rate of F ≦ V / T. The ultraviolet light source 20 starts to be turned on at the same time when the normally closed valve 53 is turned off, and is turned off after a lapse of time T. During this time, the conductivity detected by the conductivity detection electrode 30 gradually increases according to the oxidation state of the passing sample liquid portion, and eventually becomes constant at the maximum conductivity according to the lighting time of the ultraviolet light source 20 and the organic carbon content. Become. During this time, the temperature of the sample liquid rises during lighting, and falls when light is turned off due to the heat generated by the ultraviolet light source. The temperature detected by the temperature sensor of the conductivity detection electrode 30 is:
Due to the time required for the sample liquid portion that has exited the ultraviolet irradiation region to reach there and a slight response time, the rise and fall as shown in the figure is observed after the turning on and off of the ultraviolet light source.

Next, when the normally closed valve 53 is turned on and opened, most of the sample liquid flowing out of the oxidation container 10 passes through the normally closed valve 53, so that the flow rate of the sample liquid flowing into the oxidation container 10 increases rapidly. The timing at which the normally closed valve is turned on may be uniformly managed with a margin in time, or may be the time when it is confirmed that the increase in conductivity has become equal to or less than a certain value. Also,
Since the maximum value of the temperature is obtained after the maximum value of the conductivity is obtained, the temperature may be turned on when the temperature becomes the maximum.
As shown in the figure, when the normally-closed valve 53 is turned on, the conductivity rapidly decreases and returns to the base conductivity.

After the conductivity returns to the base conductivity, the normally closed valve is turned off again and the above operation is repeated. The timing of turning off the normally closed valve again may be uniformly managed by looking at a margin in time, or may be the time when it is confirmed that the decrease in the conductivity has become equal to or less than a certain value.

The data of the base conductivity and the maximum conductivity thus obtained are input to the arithmetic unit 40. Then, after temperature compensation based on the temperature sensor data,
The organic carbon content is calculated. Further, when the value of the light meter 22 becomes smaller than the predetermined value, it is determined that the ultraviolet light source 20 has deteriorated, and the arithmetic unit 40 outputs an alarm.

FIG. 10 shows experimental values obtained using an apparatus equivalent to that of FIG. Since the supply pressure of the standard liquid used as the sample liquid was insufficient, a low flow rate pump was used instead of the orifice 52. Further, a large flow rate pump was used instead of the normally closed valve 53, and when the pump was turned on, the flow rate of the sample liquid in the oxidizing apparatus 10 was increased so that the sample liquid could be replaced.

The specific conditions under which the experimental values were obtained are as follows. First, the oxidation container 10 has the structure shown in FIG. 7, in which the inner diameter of the outer cylinder is 18 mm and the outer diameter of the inner cylinder is 16 m.
m, a total length of 225 mm, and a total internal volume of 12 mL were used. Among them, the irradiation area 23 is located at a substantially middle position in the length direction, the length is 160 mm, and the volume V is 8.5 mL. The conductivity detection electrode 30 used was a flow cell type having an internal volume of about 1 mL and a cell constant of about 0.1. Oxidation container 1
0 and the conductivity detection electrode 30 were connected by a Teflon tube of about 25 mm having an inner diameter of 4 mm. As the ultraviolet light source 20, a low-pressure mercury lamp having a rating of 5 W was used, and was repeatedly turned on for 90 seconds (T = 1.5 min) and then turned off for 115 seconds.

The sample solution was F ≦ V / T = 8.5 mL / 1.
In order to satisfy 5 min = 5.7 mL / min, when the large flow rate pump was turned off, it was adjusted to pass through the oxidation vessel 10 at a flow rate F of about 4 to 5 mL / min.
When the large flow pump is turned on, about 70 mL
The sample liquid was adjusted to pass through the oxidation container 10 at a flow rate of / min. The large flow pump was turned off when the ultraviolet light source 20 was started to be turned on, and after 150 seconds, the operation was turned on for 55 seconds.

As a sample solution, a flow of a standard methanol solution of 1000 ppm (the same hereinafter in terms of carbon content) and a flow of zero water containing 4 ppb of organic carbon are combined by adjusting the flow rate ratio to obtain a solution of 4 to 1004 ppb. Was prepared and supplied. The numbers shown in FIG. 10 are the sample solution concentrations (unit: ppb) when each peak data was obtained.

As shown in FIG. 10, the conductivity peak corresponding to each concentration was obtained with good reproducibility at an interval of once every 205 seconds (about 3.5 minutes). Also, from the data of FIG.
When the relationship between the change in the conductivity (the difference between the maximum conductivity and the base conductivity) with respect to the concentration of the sample solution was determined, a good calibration curve was obtained as shown in FIG. In FIG. 10,
A slight disturbance of the peak value is observed when the concentration of the sample liquid is switched, but this is considered to be a problem of replacement delay of the sample liquid preparation side rather than a problem of the measurement device side.

Next, in order to examine the influence of the sample liquid flow rate, the flow rate F of the low flow rate pump (the flow rate when the large flow rate pump was turned off) was changed between 4.3 mL / min and 5.5 mL / min. A 54 ppb methanol standard solution prepared in the same manner as above was measured. The result is shown in FIG. The numbers in FIG. 12 are values of the flow rate F when each peak data is obtained. As shown in the figure, F ≦ V / T = 8.5 mL / 1.5
In a range satisfying the condition of min = 5.7 mL / min,
It was confirmed that a constant change in conductivity was obtained regardless of the flow rate change.

[0057]

According to the present invention, the organic carbon content can be measured at a very short interval of once every few minutes. for that reason,
Monitoring of the organic carbon content in substantially real time is possible. Moreover, since precise flow rate control is not required to obtain a measured value, the apparatus can have a simple configuration. Therefore, a low-cost and easy-to-handle organic carbon content measuring device can be provided.

[Brief description of the drawings]

FIG. 1 is an organic carbon measuring device according to an embodiment of the present invention.

FIG. 2 is an organic carbon measuring device according to another embodiment of the present invention.

FIG. 3 is an organic carbon measuring device according to another embodiment of the present invention.

FIG. 4 is an operation explanatory view of the organic carbon measuring device according to the embodiment shown in FIG. 1;

FIG. 5 is an operation explanatory view of the organic carbon measuring device according to the embodiment shown in FIG. 2 or FIG.

FIG. 6 is an organic carbon measuring device according to an embodiment of the present invention.

FIG. 7 is a specific example of an oxidation vessel used in the organic carbon measuring device according to the embodiment of the present invention, where (a) is a longitudinal sectional view,
(B) is a plan view.

FIG. 8 is another specific example of the oxidation vessel used in the organic carbon measuring device according to the embodiment of the present invention, wherein (a) is a longitudinal sectional view,
(B) is a plan view.

FIG. 9 is an operation explanatory diagram of the organic carbon measuring device according to the embodiment of the present invention.

FIG. 10 shows data obtained by measuring a methanol standard solution with the organic carbon measuring device according to the example of the present invention.

FIG. 11 is a calibration curve obtained from the data of FIG.

FIG. 12 shows data obtained by examining the influence of a flow rate change in the organic carbon measuring device according to the example of the present invention.

[Explanation of symbols]

 1,10 Oxidation container 2 UV irradiation area 20 UV light source 3,30 Conductivity detecting electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G060 AA06 AC10 AD03 AE17 AF08 AG11 FA15 FB02 HC01 HC08 HC10 HC11 HD02

Claims (11)

[Claims] 1. A sample solution is passed through an oxidation container,
The sample solution is irradiated with ultraviolet light for a certain period of time, then the irradiation is stopped, and the base conductivity before starting the lighting of the ultraviolet light and the maximum conductivity after stopping irradiation are provided near the outlet of the oxidation container. In the method for measuring the organic carbon content in the sample solution from the difference between the base conductivity and the maximum conductivity, the flow rate F through which the sample solution passes through the oxidation vessel, The organic volume content of the organic carbon content, wherein the inner volume V of the oxidizing vessel on the upstream side of the conductivity detection electrode and the irradiation time T of the ultraviolet light is in a relationship of F ≦ V / T. Measuring method. 2. After the maximum conductivity is measured by the conductivity detection electrode, a flow rate of the sample solution passing through the oxidation container is increased to replace the sample solution in the oxidation container. The method for measuring an organic carbon content according to claim 1. 3. The method for measuring an organic carbon content according to claim 1, wherein a photocatalyst is used to promote ultraviolet oxidation of the organic carbon in the sample liquid. 4. The organic light emitting device according to claim 1, wherein a light amount of the ultraviolet light is measured, and an alarm is output when the measured light amount becomes smaller than a predetermined value. Method for measuring carbon content. 5. An oxidation container through which a sample solution passes, an ultraviolet light source for irradiating the sample solution in the oxidation container with ultraviolet light, lighting control means for turning on the ultraviolet light source for a predetermined time and then turning off the light source;
The conductivity detection electrode provided in the vicinity of the outlet of the oxidation vessel, and the difference between the base conductivity before the start of lighting of the ultraviolet light measured by the conductivity detection electrode and the maximum conductivity after the light is turned off in this sample liquid. And a flow rate F through which the sample solution passes through the inside of the oxidation container, and an inner volume of the oxidation container on the upstream side of the conductivity detection electrode where the ultraviolet ray is irradiated. An apparatus for measuring an organic carbon content, comprising: a flow rate control means for controlling the flow rate F so that V and the irradiation time T of ultraviolet light have a relation of F ≦ V / T. 6. After the maximum conductivity is measured by the conductivity detection electrode, the flow rate control means increases the flow rate of the sample liquid passing through the oxidation vessel to replace the sample liquid in the oxidation vessel. The apparatus for measuring an organic carbon content according to claim 5, wherein: 7. The organic carbon content measuring device according to claim 5, wherein a photocatalyst for promoting ultraviolet oxidation of organic carbon in the sample liquid is provided in the oxidation container. . 8. The oxidation vessel has an outer cylinder and an inner cylinder made of a material substantially transmitting ultraviolet light, and has a double tube structure in which a sample liquid passes between the outer cylinder and the inner cylinder. The apparatus for measuring an organic carbon content according to claim 7, wherein a photocatalyst is coated inside the outer cylinder, and the ultraviolet light source is accommodated inside the inner cylinder. 9. The oxidation vessel has an outer cylinder and an inner cylinder made of a material substantially transmitting ultraviolet light, and has a double tube structure in which a sample liquid passes between the outer cylinder and the inner cylinder. 8. The organic carbon content measuring device according to claim 7, wherein a photocatalyst is coated inside the outer cylinder, and the inner cylinder is formed from an outer tube of the ultraviolet light source. 10. The apparatus for measuring an organic carbon content according to claim 5, further comprising a light meter for measuring the amount of ultraviolet light from the ultraviolet light source. 11. The apparatus according to claim 5, further comprising means for confirming a flow rate F of the sample solution passing through the inside of the oxidation vessel.
The organic carbon content measuring device according to any one of claims 1 to 10.