JP2001281187A - Concentration measuring method for polycarboxylic acids and instrument therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentration measuring method for polycarboxylic acids and an instrument therefore, capable of quantitatively determining simply and rapidly the concentration of polycarboxylic acids in a sample with high sensitivity by means of highly accurate and highly sensitive detection of an increase in its electrical conductivity. SOLUTION: The sample containing polycarboxylic acids is oxidated. A difference between the electrical conductivity of the sample before the oxidation and that after the oxidation is detected by using a differential conductivity meter, which has at least two conductance cells each having an electrode and disposed in a position where the sample is placed before the oxidation and a position where the sample is placed after the oxidation, respectively, and outputs a difference between signals themselves from the two conductance cells as a difference in electrical conductivity of the sample between the positions of the two conductance cells. Thus, the increase in the electrical conductivity caused by the oxidation/decomposition of the polycarboxylic acids is measured and the concentration of the polycarboxylic acids in the sample is quantitatively determined the increase in the electrical conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the concentration of polycarboxylic acids, and more particularly, to oxidizing a sample containing polycarboxylic acids and measuring the amount of increase in electric conductivity caused by oxidative decomposition of the polycarboxylic acids. Highly sensitive, simple and fast detection of polycarboxylic acids by measuring with a new electrical conductivity meter that has both stability and stability, and enabling the concentration of polycarboxylic acids in the sample to be quantified from the increase in electrical conductivity And a method and apparatus for performing the method.

[0002]

BACKGROUND OF THE INVENTION Polycarboxylic acids are widely used in many aqueous systems. For example, using the function as a scale inhibitor, sludge dispersant, anticorrosive,
Besides being added to cooling water and boiler water, it is used as a water treatment additive for reverse osmosis membrane devices, sugar refining, paper manufacturing, geothermal processes, and oil wells. In addition to being used as a flocculant in wastewater treatment systems, it is also used as a detergent additive and an anti-film-forming agent. In these fields of application, polycarboxylic acids are added to the system in order to exhibit the above functions (prevention of scale, dispersion of sludge, corrosion prevention, aggregation, etc.). In order to exert the effect, it is necessary to appropriately control the concentration of the polycarboxylic acids in the system since there is a lower limit or an optimum value for the concentration of the polycarboxylic acids. However, in most applications, since the concentration of polycarboxylic acids in the system is quite low, there is no simple detection method, and detection is conventionally performed by colorimetry or turbidimetry, which is a complicated manual analysis method. I went. Since this method is difficult to automate, detection requires a lot of time and cost, and hinders appropriate concentration management.

Therefore, as a method for solving these problems, there has been proposed a method for relatively easily detecting polycarboxylic acids using fluorescence analysis (Japanese Patent Laid-Open No. 4-233).
No. 918). However, this method is inferior in analytical sensitivity, so that the sensitivity is insufficient to detect trace amounts of polycarboxylic acids in the system, and the selectivity of the fluorescent analysis method is low. There was a problem that detection of carboxylic acids was hindered. Further, since ordinary polycarboxylic acids do not emit fluorescence, it is necessary to introduce a fluorescent probe into the polycarboxylic acids in order to use the fluorescence analysis method, and the problem that the production cost of the polycarboxylic acids increases, The introduction of the fluorescent probe has a problem that the original function of the polycarboxylic acids is reduced or lost.

[0004] As another method, a method for relatively easily detecting polycarboxylic acids using an immunoassay has been proposed (JP-A-9-218199). However, although this method has no problem in sensitivity, the cost required for measurement is high, and a continuous flow analysis method (FIA: Flow) is required.
However, it has drawbacks such as difficulty in application to fully automatic continuous measurement typified by Injection Analysis.

The present applicant has previously proposed a method for detecting polycarboxylic acids by utilizing a chemiluminescence reaction (Japanese Patent Application Nos. 11-82687 and 11-16901).
No. 6). This method is more sensitive than the absorbance method and the fluorescence method, has a wide quantitative range, and has a fast response time (the time required for the luminescence reaction is short), so it can be widely used especially as a highly sensitive detection method in distribution systems. However, expensive ruthenium complexes must be used as detection reagents (chemiluminescent substances), and electrolytic oxidation equipment that requires expensive periodic maintenance and inspection work as pretreatment equipment for detection reagents There were problems such as necessity.

On the other hand, as a method of measuring the amount of organic matter in an aqueous solution, the amount of organic matter is quantified by oxidizing and decomposing organic matter in an aqueous solution and measuring the amount of generated carbon dioxide gas and the amount of increase in electric conductivity. A method has been proposed (Japanese Patent No. 2706290). This method is noteworthy because the amount of organic substances in an aqueous solution can be easily and inexpensively quantified. However, when the amount of generated carbon dioxide is targeted for detection, the detection sensitivity is low, so that the amount of organic substances at the μg / L level is low. Quantification was not possible. On the other hand, if the amount of increase in electrical conductivity is targeted for detection, there is no problem in terms of detection sensitivity, but conventional conductivity meters are inferior in stability. Could not do. Also, in a system in which a large amount of electrolyte components coexist in an aqueous solution, the background of the electrical conductivity becomes very large, and therefore, a conventional electrical conductivity meter measures a small increase in electrical conductivity caused by oxidative decomposition. It was difficult to do. Furthermore, in this method, in order to enhance the detection sensitivity, it is necessary to completely oxidize and decompose the organic substance in the aqueous solution, and a method of circulating the aqueous solution containing the organic substance many times through the oxidizing apparatus is adopted. As a result, the measurement had to be performed in a batch system, and continuous measurement could not be performed.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to make it possible to detect a minute increase in electric conductivity with higher accuracy and sensitivity and to increase the electric conductivity. Through the detection of the amount, the concentration of polycarboxylic acids in the sample can be quantified with high sensitivity, simply and quickly,
Moreover, an object of the present invention is to provide a method and an apparatus for measuring the concentration of polycarboxylic acids, which can easily perform continuous measurement.

[0008]

In order to solve the above problems, a method for measuring the concentration of polycarboxylic acids according to the present invention comprises:
A sample containing polycarboxylic acids is oxidized, and the difference between the conductivity before oxidation of the sample and the conductivity after oxidation is determined by oxidizing the conductivity measurement cell having at least two electrodes with the position before oxidation. And a differential conductivity meter that outputs the difference between the detection signals from the two conductivity measurement cells as the difference in the electrical conductivity of the sample between the two conductivity measurement cells. The method comprises measuring the amount of increase in electric conductivity caused by oxidative decomposition of polycarboxylic acids, and quantifying the concentration of polycarboxylic acid in the sample from the amount of increase in electric conductivity.

In this method, a solid oxidizing agent having a photocatalyst immobilized on a carrier is used as an oxidizing agent for a sample, and the sample is oxidized by irradiating light with the oxidizing agent in contact with the sample. Is preferred. As the photocatalyst, for example, titanium oxide can be used.

In the measurement of the increase in electric conductivity, only the electric conductivity of the sample can be directly measured. However, a standard solution corresponding to the electric conductivity of the sample is used as a carrier liquid. It is also possible to continuously oxidize the sample by injecting the sample into the carrier liquid, and to continuously measure the increase in the electric conductivity.

An apparatus for measuring the concentration of polycarboxylic acids according to the present invention comprises a sample measurement flow channel through which a sample containing polycarboxylic acids flows, oxidizing means for the sample disposed in the sample measurement flow channel, An electrical conductivity measuring cell having at least two electrodes disposed upstream and downstream of the oxidizing means, and a difference between detection signals themselves from the electrical conductivity measuring cells is determined by a position of the electrical conductivity measuring cells. A differential conductivity meter that outputs the difference in electrical conductivity of the sample between the two, and from the output of the differential conductivity meter, measures the increase in electrical conductivity caused by oxidative decomposition of polycarboxylic acids, It is characterized in that the polycarboxylic acid concentration in the sample is determined from the amount of increase in conductivity.

In the method and apparatus for measuring the concentration of polycarboxylic acids as described above, the concentration of polycarboxylic acids in the sample is quantified from the increase in electric conductivity of the sample before and after oxidation, and the measurement of the increase in electric conductivity is performed. A difference conductivity meter that outputs a difference between detection signals from the two conductivity measurement cells is used. In this differential conductivity meter, basically, not the absolute value of the electrical conductivity of the sample but the change (difference) in the electrical conductivity is detected. Irrespective of the fluctuation of the ground, only the increase in the electrical conductivity of the sample before and after the oxidation is accurately detected, and even with a small increase in the electrical conductivity, an extremely sensitive measurement can be performed. In addition, since the sample can be measured directly, large-scale auxiliary equipment for measurement is not required, and continuous measurement can be easily performed.
In addition, rapid measurement in almost real time becomes possible.
Further, if a sample utilizing photocatalytic activity such as titanium oxide is used for oxidizing a sample, a stable oxidizing action and, consequently, a stable measurement of an increase in electric conductivity can be performed. As described above, the concentration of the polycarboxylic acid in the sample can be simply, quickly, and accurately determined from the increase in electric conductivity measured with high accuracy and high sensitivity.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail together with preferred embodiments. The present invention measures the concentration of polycarboxylic acids in a sample.
The polycarboxylic acids to be detected in the present invention are not particularly limited, and examples thereof include the following. That is, the polycarboxylic acids to be detected in the present invention are a homopolymer or a copolymer comprising a carboxylic acid and a polymerizable monomer having an unsaturated double bond, and salts thereof. Examples of these polymerizable monomers include acrylic acid, methacrylic acid, vinyl acetic acid, crotonic acid, maleic acid, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, 1,2,3,6-tetrahydrophthalic acid and These alkali metal salts, alkaline earth metal salts, ammonium salts, maleic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, 3,6-epoxy-1,2,2
3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, bicyclo [2.2.
2] -5-octene-2,3-dicarboxylic anhydride, 3
-Methyl-1,2,6-tetrahydrophthalic anhydride,
2-methyl-1,3,6-tetrahydrophthalic anhydride and the like. Among these polymerizable monomers, particularly preferred are acrylic acid, methacrylic acid and maleic anhydride.

The polycarboxylic acids to be detected in the present invention contain less than 80% by weight of a polymerizable monomer containing no carboxylic acid but having an unsaturated double bond as long as the polymer is water-soluble. May be included in quantity. Examples of these polymerizable monomers include C1 of acrylic acid or methacrylic acid.
To C4 alkyl ester (specific examples include methyl acrylate, ethyl acrylate, butyl acrylate,
Methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, etc.), hydroxyalkyl esters of acrylic acid or methacrylic acid (specific examples include hydroxyethyl acrylate,
Hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and the like, and other esters of acrylic acid or methacrylic acid (as specific examples, 2-sulfoethyl acrylate, 3-sulfopropyl acrylate, 2-sulfatoethyl acrylate, 2-N, N-dimethylaminoethyl acrylate, 2-sulfoethyl methacrylate, 3-sulfopropyl methacrylate, 2-sulfatoethyl methacrylate, phosphoethyl methacrylate, ethylene glycol diacrylate, trimethylolpropane triacrylate, etc.), none Substituted and substituted (meth) acrylamides (specific examples include acrylamide, methacrylamide, Nt-butylacrylamide, N-methylacrylamide, N, N-dimethyl) Acrylamide, 3-N,
N-dimethylaminopropylacrylamide, acrylamidoglycolic acid, etc.), (meth) acrylonitrile (specific examples are acrylonitrile, methacrylonitrile), sulfonic acid-containing monomers (specific examples are allylsulfonic acid, vinylsulfonic acid, p-styrenesulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, etc.), phosphonic acid-containing monomers (specific examples include allylphosphonic acid, vinylphosphonic acid, etc.), and other monomers (specific examples) Is allyl alcohol, 2-vinylpyridine, 4-vinylpyridine, N-vinylpyrrolidone,
N-vinylformamide, N-vinylacetamide, N
-Vinylimidazole, N-vinylimidazoline, 2-
Vinylimidazole, 2-vinylimidazoline, N-acryloylmorpholine, acrolein, diallyl phthalate, vinyl acetate, styrene, methacryloyl sulfonate, 1-allyloxy-2-hydroxypropyl sulfonate, etc.) and alkali metal salts of the above monomers, alkaline earth Metal salts, ammonium salts and the like.

The molecular weight of the polycarboxylic acids to be detected in the present invention is not particularly limited, but polymers in the range of 500 to 200,000,000 can be detected in the present invention.

The method for oxidizing a sample containing a phosphorus compound used in the present invention is not particularly limited, and known oxidation methods can be used alone or in combination. Specific examples of the oxidation method include ozone as an oxidizing agent, persulfates such as potassium peroxodisulfate, hydrogen peroxide, halogen oxides such as sodium hypochlorite, and the like. In the coexistence of persulfate, hydrogen peroxide and ozone, the method of oxidizing by irradiating light, the oxidation by Fenton reaction, the method of oxidizing by electrode reaction, the coexistence of photocatalyst represented by titanium dioxide,
A method of oxidizing by irradiating light may be used. Among these methods, the method preferably used in the present invention, because of its high oxidizing ability and the fact that a special oxidation treatment device is not required, and the waste liquid treatment after oxidation is not required,
In this method, light is irradiated to oxidize in the presence of a photocatalyst.
A particularly preferable method is a method in which oxidation is performed by irradiating light in the presence of a solid oxidizing agent in which a photocatalyst is immobilized on a carrier.

As the photocatalyst carrier used in the present invention, for example, the present applicant has previously filed Japanese Patent Application No. 11-14395.
The photocatalyst carrier proposed in No. 8 can be used. The photocatalyst referred to here is one that, when a photocatalyst particle is irradiated with light having energy equal to or greater than its band gap, an electron is generated in a conduction band and a hole is generated in a valence band by photoexcitation. The oxidative decomposition of phosphorus compounds in a sample is performed by utilizing the strong oxidizing power of holes. In order to effectively utilize the oxidation reaction due to the holes excited by the photons, the reaction proceeds only on the surface of the photocatalyst particles, and since the reaction proceeds only at the site irradiated with light,
It is necessary that the catalyst has a large surface area and that the contact with the substance to be decomposed is sufficiently achieved. Also, from the oxidation mechanism, to make the reaction proceed quickly,
It is necessary that an electron acceptor (oxidizing agent) that quickly removes electrons in the photocatalyst generated by light irradiation from the photocatalyst exists in the system.

In the present invention, it is preferable to use the photocatalyst carrier previously proposed by the present applicant in Japanese Patent Application No. 11-143958, and the photocatalyst carrier comprises a carrier (A) and a photocatalyst particle (B). Unlike the mere mixture of the carrier (A) and the carrier (A), the particles (B) are supported on the surface of the carrier (A) by thermal fusion, and the particles (B) are partially exposed. Further, particles (B) are formed on the surface of the carrier (A).
Are multiply stacked, even if a part of the particles (B) is peeled or dropped due to deterioration of the surface of the photocatalyst carrier, the particles (B) thereunder appear one after another and are exposed. It has become. Therefore, by using such a photocatalyst carrier, it is possible to maintain the photocatalytic activity for a long period of time, and in the oxidation of the sample in the present invention, a stable oxidizing action can be maintained for a long period of time.

The shape of such a photocatalyst carrier is arbitrary, but a substantially spherical or disk-like shape is preferred in view of the simplicity of the manufacturing process. A substantially spherical photocatalyst carrier is preferable in terms of handleability, and a disk-shaped one is preferable in that the photocatalyst particles (B) have a large exposed surface area. The size of the photocatalyst carrier is not particularly limited and can be set as appropriate. For example, in the case of a substantially spherical shape, the particle size is 0.1 mm to 30 m.
m, preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm.

Examples of the carrier (A) of the photocatalyst carrier used in the present invention include olefin homopolymers such as polyethylene and polypropylene, copolymers of olefins, olefins and other polymerizable monomers. And poly (meth) acrylates such as polyvinyl chloride, polyvinylidene chloride, polystyrene, and polymethyl methacrylate; polyamides; and polyesters such as polyethylene terephthalate and polyethylene naphthalate. Among these, when used as a material for the carrier (A), the particles (B) are firmly
Particularly preferred thermoplastic polymers in that they can easily carry are olefin homopolymers, copolymers of olefins, and copolymers of olefins and other polymerizable monomers.

Examples of the particles (B) constituting the photocatalyst carrier used in the present invention include, for example, titanium dioxide, strontium titanate, zinc oxide, iron oxide, zirconium oxide, niobium oxide, tungsten oxide, tin oxide, Examples include particles of a substance having a photocatalytic action such as cadmium sulfide, cadmium telluride, cadmium selenide, molybdenum sulfide, and silicon, and at least one kind of particles can be selected from these. Particularly preferred is titanium dioxide which exhibits excellent photocatalytic performance. Titanium dioxide has anatase-type and rutile-type crystal structures, and since anatase-type titanium dioxide has higher photocatalytic activity, it is usually used.

Further, the particle (B) may further use a particle having a metal such as platinum, rhodium, ruthenium, nickel or the like or an oxide or hydroxide of the metal supported on the surface. It is possible to improve the photocatalytic efficiency even with a very small amount of support. The particles (B)
A material having a substance having a luminous action on its surface may be used. As such a phosphorescent substance, for example, a substance in which sulfide, sulfate, silicate, or the like of an alkaline earth metal is used as a main material, and to which lead, manganese, bismuth, or the like is added as an activator, can be suitably used. As a specific example, Ba
Examples thereof include SO ₄ / Pb, CaSiO ₃ / Pb, and CaS / Bi. These may be used alone or in combination of two or more. Luminescent substances are generally called fluorescent substances, luminous substances, etc., and are substances that can temporarily convert energy such as visible light, ultraviolet rays, and radiation into chemical energy and store it, and radiate the energy as light energy at any time. By supporting the particles on the particles (B), it is also possible to improve the light use efficiency.

The amount of the particles (B) to be carried on the carrier (A) cannot be specified because it greatly varies depending on the type of the photocatalyst particles, the type of the thermoplastic polymer, and the like.
Preferably 0.1 to 8 based on the total weight of the particles (B).
0% by weight, more preferably 1% to 50% by weight.
If the amount is less than 0.1% by weight, it becomes difficult for the particles (B) to cover the entire surface of the carrier (A),
It is meaningless to increase the number only by increasing the number of photocatalyst particles buried inside the photocatalyst carrier more than necessary.

The specific gravity of the photocatalyst carrier is not particularly limited, but is preferably 0.7 to 1.
3, more preferably 0.9 to 1.1. When the specific gravity is less than 0.7, the photocatalyst carrier always floats on the water surface even with stirring, and the reaction efficiency is poor,
If it exceeds 1.3, it will always sink into the water bottom even with stirring, and it will be difficult to efficiently irradiate light. However, when the photocatalyst carrier is packed in a column to form a fixed bed and is used as an apparatus for oxidizing a sample, the specific gravity may exceed this range. The range of the above specific gravity is important in the case of a fluidized bed system in which the light-supported catalyst is dispersed in water and stirred. In the present invention, either a fixed bed or a fluidized bed can be suitably used as the oxidizing device.

Further, in order for the oxidation reaction of the photocatalyst to proceed rapidly, it is necessary that an electron acceptor (oxidizing agent) in the system which rapidly removes electrons in the photocatalyst generated by light irradiation from the photocatalyst exists. is there. Examples of such an electron acceptor include oxygen, ozone, hydrogen peroxide and the like, and are suitably used in the present invention.

The wavelength of light required when using a photocatalyst as an oxidizing agent is not particularly limited as long as it includes a wavelength band necessary for exciting and activating the photocatalyst. 380 to 400 nm or less). Therefore, sunlight, a fluorescent lamp, a black light, a cold cathode tube, a mercury lamp, a xenon lamp, or the like can be used as the light source.

Next, a difference conductivity meter used as a device for detecting an increase in electric conductivity in the present invention will be described. In the present invention, a sample containing polycarboxylic acids is oxidized using the oxidizing means as described above, and the difference between the electrical conductivity of the sample before oxidation and the electrical conductivity after oxidation, that is, the oxidation of the polycarboxylic acids, The amount of increase in electrical conductivity caused by the decomposition is measured by a differential conductivity meter. This differential conductivity meter is
An electric conductivity measuring cell having at least two electrodes is arranged at a position before oxidation of a sample and at a position after oxidation of a sample, and a difference between detection signals themselves from both electric conductivity measuring cells is determined by a position of each electric conductivity measuring cell. It is output as the difference in the electrical conductivity of the sample between the two. Therefore, this method is fundamentally different from the method of measuring the absolute value of the electrical conductivity of the sample at each measurement position by simply using two conventional electrical conductivity meters and obtaining the increase in electrical conductivity from the difference between the two. Things. The concentration of the polycarboxylic acid in the sample is quantified from the increase in the electric conductivity caused by the oxidative decomposition of the polycarboxylic acids, which is detected using the differential conductivity meter.

FIG. 1 shows an example of a differential conductivity meter used in the apparatus for measuring the concentration of polycarboxylic acids according to the present invention.
In the differential conductivity meter 1 shown in FIG. 1, an alternating current from an AC oscillator 2 is supplied to each of the electric conductivity measuring cells 3 and 4, and one of the electric conductivity measuring cells 3 has a magnification setting device 5. The alternating current that has been amplified to a predetermined magnification by the phase inverting amplifier 6 and is inverted in phase is supplied, and the alternating current amplified by the amplifier 7 at a constant magnification is supplied to the other electric conductivity measurement cell 4. Supplied without phase inversion. The output side of each of the conductivity measurement cells 3 and 4 is connected, and the phase of the one supplied alternating current is inverted, so that the difference between the detection signals themselves from the two conductivity measurement cells 3 and 4 is calculated. A subtraction process is performed. The signal subjected to the subtraction processing is amplified by an amplifier 9 with a sensitivity (measurement range) switch 8 and output as a predetermined one output signal 10. Therefore, the output signal 10 indicates a difference or a change between the detected electric conductivities of the electric conductivity measuring cells 3 and 4.

As described above, instead of calculating the difference or the change from the absolute value of the detection value output from each electric conductivity measuring device, each electric conductivity measurement is performed in one difference conductivity meter 1. Since the detection signals from the cells 3 and 4 are subtracted, only the difference or the difference between the detected electric conductivities of the electric conductivity measuring cells 3 and 4 can be accurately extracted. In addition, the measurement range at the time of this measurement may be adjusted not for the absolute value of the electric conductivity, but for the difference or change in the electric conductivity to be detected. Even when the difference or the change is small relative to the absolute value, the measurement can be adjusted to the optimum measurement range regardless of the absolute value of the electric conductivity, and extremely high-precision and high-sensitivity measurement becomes possible.

Further, the magnification setting device 5 is provided so that the level of the current supplied to one of the conductivity measuring cells 3 can be appropriately switched, so that it can be applied to either the concentration system or the dilution system. Optimal sensitivity adjustment becomes possible.
In addition, since the sensitivity (measurement range) switch 8 is also provided on the output side, the level of the finally output signal can be adjusted to the optimum level, and the difference or change in the electric conductivity measurement can be adjusted to the optimum sensitivity. Can be measured. As a result, data of the difference or change of the electric conductivity measurement with extremely high reliability can be obtained with high accuracy and high sensitivity.

Such a differential conductivity meter can be configured, for example, as shown in FIG. The differential conductivity meter 11 shown in FIG.
Means that at least two cells (in this embodiment, a two-cell configuration) having at least two electrodes (shown in a three-electrode configuration in this embodiment) in contact with a substance to be measured (sample). ). In the present embodiment, each of the electric conductivity measurement cells 12 and 13 (shown as cell 1 and cell 2 in FIG. 2) subtracts the detection signal itself from each electric conductivity measurement cell 12 and 13. It is electrically connected to be processed.

The electric conductivity measuring cells 12 and 13 are electrically connected in parallel, and the electric conductivity measuring cells 12 and 13 are electrically connected in parallel.
The 13 current supply electrodes 12a and 13a are supplied with an in-phase AC current from an AC oscillator 14 as a power supply. The electric conductivity detection electrodes 12b and 13b of the electric conductivity measurement cells 12 and 13 are electrically connected to each other, and the values of the detection signals from the two detection electrodes 12b and 13b are subtracted as follows. It has become. In front of the current supply electrode 13a of the electric conductivity measuring cell 13, a phase inverter 15 capable of amplifying or reducing the value of the supplied alternating current at a predetermined magnification is provided. In this case, the level of the electric conductivity of the substance to be detected can be made different from that of the electric conductivity measuring cell 12, and the phase of the detection signal can be inverted. By doing so, the detection signal itself from each of the electric conductivity measurement cells 12 and 13 is substantially subtracted.

The signal which has been subjected to the electrical arithmetic processing, that is, the signal obtained from the connection point of the electric conductivity detecting electrodes 12b and 13b, is amplified by one amplifier 16 to an appropriate level as an output signal. It has become. At this time, the measurement range switch 17 can select the optimum measurement range according to the measurement target.

In this embodiment, the signal from the amplifier 16 is synchronized with the output side of the AC oscillator 14 by the synchronous rectifier 19 after the temperature compensation for the measurement environment is performed by the temperature compensator 18. The signal is amplified by an amplifier 21 with a range adjuster 20 so that the signal becomes an optimal level signal for various controls and output display.
2 is taken out.

In the above-described differential conductivity meter, by using a time delay column having a predetermined capacity, it is possible to accurately measure a temporal change in the electrical conductivity of a sample (substance to be measured). Become. For example, as shown in FIG. 3, when it is desired to measure a change in the electrical conductivity measurement between different positions in the flow direction of the water flowing in the flowing water pipe 52, the difference conductivity meter 51 is moved to the upstream position 53. For example, the sample water is provided via a venturi tube 54 so that water can be collected as sample water. After the electric conductivity of the sample water is first detected by one electric conductivity measuring cell 55, the sample water is sent to the other electric conductivity measuring cell 57 through the time delay column 56, where the electric conductivity of the sample water is again measured. Is measured, and the sample water after the measurement is returned to the position 58 on the downstream side of the water pipe 52. The time delay column 56 is formed, for example, by winding a thin tube in a spiral shape so that the water flow time from the inflow end to the outflow end can be adjusted. In this embodiment, substantially the upstream side of the flowing water pipe 52 is provided. Position 5
It corresponds to the water passage time from 3 to the downstream position 58.

By providing such a time delay column 56,
By shifting the detection timing of the electric conductivity with respect to the same sample water in time, it is possible to observe how the electric conductivity changes during that time. By using the difference conductivity meter 51 according to the present invention for this observation, a change in the electric conductivity is detected with high reliability and high accuracy and high sensitivity. Therefore, by configuring the inside of the time delay column 56 as a means for oxidizing a sample, it becomes possible to oxidize a desired sample in a desired time in the present invention.

In the present invention, the structure of each electric conductivity measuring cell itself is not particularly limited, and any electric conductivity measuring cell having at least two electrodes in contact with a substance to be measured (sample) may be used. At least two electrodes in each electric conductivity measuring cell include an electric conductivity detecting electrode and a current supply electrode, and in the case of a three-electrode configuration, one of them can be a ground electrode. It is preferable that an alternating current is supplied to the current supply electrode, but a configuration in which a direct current is supplied is also possible.

FIG. 4 shows a schematic configuration of a two-electrode conductivity measuring cell applicable to the present invention. The electric conductivity measurement cell 61 shown in FIG. 4 is provided with a power supply electrode 64 and an electric conductivity for a fluid 63 to be measured as a substance to be measured flowing into the measurement tube 62 or stored in the measurement tube 62. The detection electrodes 65 are spaced apart from each other. An AC constant voltage is applied to the power supply electrode 64 from, for example, a power supply (not shown) via an amplifier 66, and the electric conductivity detection electrode 65 is applied.
Are supplied to the above-described addition and subtraction processing.

In the electric conductivity measuring cell 61 having the above-described two-pole structure, the measuring tube 62 is made of an insulator (for example, a vinyl chloride tube) at least at the electric conductivity measuring portion.
However, usually, at any position of the extension portion, it is often in a substantially grounded state,
Due to the grounding condition, noise from the surrounding environment may be picked up.

In order to remove the influence of such noise, it is preferable to use a three-electrode conductivity measuring cell as shown in FIGS. 5 and 6, for example. In the electric conductivity measuring cell 71 shown in FIG.
Three electrodes 74, 75, 76 that are in contact with the fluid 73 to be measured are provided for the fluid 73 to be measured as a substance to be measured flowing therein or stored in the measurement tube 72. . The three electrodes include an electric conductivity detection electrode 74 for detecting electric conductivity, and two alternating current supply electrodes 75 arranged on both sides of the electric conductivity detection electrode 74 at intervals. 76. The two AC current supply electrodes 75 and 76 are connected via an amplifier 77 to
In-phase alternating current is supplied at a constant voltage of the same potential. The detection current from the electric conductivity detection electrode 74 is subjected to the aforementioned subtraction processing.

In the electric conductivity measuring cell 71 shown in FIG. 5, the electric conductivity detecting electrodes 74 are arranged on both sides thereof, and two alternating current supplying electrodes 75 to which an in-phase alternating current is supplied, 76 provides an electrical shield for a ground point that may be present anywhere on the extension of measurement tube 72. That is, a constant voltage AC current is supplied to the two AC current supply electrodes 75 and 76 in the same phase, and the potential difference between the electric conductivity detection electrode 74 and the AC current supply electrodes 75 and 76 is always a predetermined constant. Since this value is maintained, there is substantially no electric resistance between the electric conductivity detecting electrode 74 and the external grounding point. Therefore, in the cell configuration shown in FIG. 4, the resistance value between the electric conductivity detection electrode and the external ground point and the influence on the output current from the electric conductivity detection electrode due to the change in the resistance value are not affected. , Virtually completely gone. In other words, there is no leakage current from the electric conductivity detecting electrode 74 to the external ground point. As a result, the output current from the electric conductivity detection electrode 74 is always taken out without any disturbance, and variations and fluctuations due to the disturbance are prevented, so that high-precision electric conductivity measurement is always performed stably. .

In the electric conductivity measuring cell 81 shown in FIG. 6, a fluid 83 to be measured as a substance to be measured flowing into an insulated measuring tube 82 or stored in the measuring tube 82 is used. , Three electrodes 84, 85, 86 in contact with the fluid 83 to be measured. The three electrodes include an electric conductivity detection electrode 84 for detecting electric conductivity, an alternating current supply electrode 85 arranged on one side of the electric conductivity detection electrode at an interval, and an electric conductivity detection electrode. And a ground electrode 86 arranged at an interval on the opposite side of the use electrode 84. A predetermined AC current is supplied at a constant voltage to the AC current supply electrode 85 via an amplifier 87. The detection current from the electric conductivity detection electrode 84 is subjected to the aforementioned subtraction processing.

In the electric conductivity measuring cell 81 shown in FIG. 6, an alternating current is supplied at a constant voltage only to the alternating current supplying electrode 85, and the ground electrode 86 is forcibly set to the potential 0 by grounding. Electrodes 85 and 86 are arranged on both sides of the electric conductivity detection electrode 84. Therefore, the electrode 8
The electrical circuit between the terminals 5 and 86 is so-called resistance-divided by an electrical conductivity detecting electrode 84 in terms of an electric circuit. In the circuit between the electrodes 85 and 86, the electrode 85
Is supplied with a predetermined constant-voltage alternating current, and the potential of the electrode 86 is forcibly set to 0 at all times by grounding, and this state is always stable. That is, even if one of the extending portions of the measuring tube 82 is grounded, there is no room for the resistance or the like between the grounding point and the electric conductivity detecting electrode 84 to enter. The current extracted from the degree detection electrode 84 does not shift or fluctuate. Therefore, the output current from the electric conductivity detecting electrode 84 is always taken out in a state without disturbance, and the variation and fluctuation due to the disturbance are prevented, and the measurement of electric conductivity with high accuracy is always performed stably. become.

In the present invention, the mechanical structure of the electric conductivity measuring cell is not particularly limited, and may be, for example, a structure as shown in FIG. In the electric conductivity measuring cell 91 shown in FIG. 7, for example, as shown in FIG.
Electrode for measuring electric conductivity 94 having an electrode surface formed by 3
Is preferably used. The titanium oxide layer 93 is formed on the surface of the electrode body 92 made of a conductive metal by surface treatment such as sputtering or plating, or formed by oxidizing the surface of the electrode body 92 made of titanium metal. Have been. The oxidation is performed by electrolysis or air oxidation.

The electric conductivity measuring electrodes 94 are used as electrodes corresponding to the two or three electrodes shown in FIGS. 4 to 6, and as shown in FIG. Buried with the electrode surface exposed.
In the electric conductivity measuring cell 91 shown in FIG.
4 are arranged in a row, electrodes 94a on both sides and an electrode 94b are electrodes for alternating current supply connected to a power source, and a central electrode 9
4c constitutes an electric conductivity detection electrode that functions as an electric conductivity detection sensor.

The electrode holder 95 is fixed at a predetermined position on the base 96. The base 96 has an inflow port 97 through which a fluid to be measured (for example, an aqueous solution) flows in and an outflow port 98 through which the fluid to be measured, a flow hole 99 and a flow hole 1 for measuring electric conductivity.
00 is provided. The electrode holder 95 has a flow hole 1
01 and a flow hole 102 are provided. The flow hole 101 is a flow hole 99 of the base, and the flow hole 102 is a flow hole 10 of the base.
0 are arranged so as to communicate with each other. Inlet 9
7 flows into the internal passage 1 of the base 96.
03, the flow holes 99, and the flow holes 101 of the electrode holder 95, flow into the measured substance storage space 104 formed on the electrode surface side of each electrode 94. Measured substance storage space 104
Forms a flow path for measuring the electrical conductivity of the fluid to be measured. The fluid from the substance storage space 104 is stored in the electrode holder 95.
Through hole 102, through hole 100 in base 96, internal passage 1
Through the outlet 05, it flows out of the outlet 98.

The base 96 has electrodes 94a, 94b, 9
4c at positions corresponding to the through holes 106a, 106b, 10
6c are drilled and the through holes 106a, 106b, 1
Necessary electric wiring is drawn out through 06c.

In the present embodiment, the substance-to-be-measured storage space 104 is formed by a sheet-like packing 107 and a transparent glass plate 108 as a light-transmitting member that is disposed opposite to the electrode holder 95 with the packing 107 interposed therebetween. It is defined. It is preferable that the surface of the glass plate 108 on the side of the substance storage space 104 is also coated with titanium oxide so as not to impair the translucency. The electric conductivity of the fluid flowing in the measured substance storage space 104 is measured.

The electrode holder 95, the packing 107 and the glass plate 108 are connected to the cover 110 via bolts 109.
Thereby, it is fixed to one surface side of the base 96. Cover body 11
At 0, a window 111 for light transmission is opened. This window 1
Through 11, light from a light irradiation means 112 arranged outside is irradiated. The irradiated light is irradiated from the window 111 through the glass plate 108 to the titanium oxide layer 93 forming the electrode surfaces of the electrodes 94a, 94b, and 94c.
Light having a wavelength that causes the titanium oxide layer 93 to exhibit photocatalytic activity is selected as the irradiation light. For example, ultraviolet light of a specific wavelength (for example, a wavelength of 300 to 400 nm) can be used, and as the light irradiation means 112, for example, a black light that emits ultraviolet light can be used.

With such an electric conductivity measuring cell 91, the titanium oxide layer 93 provided on the surface of each of the electrodes 94a, 94b, 94c exhibits photocatalytic activity by light irradiation by the light irradiation means 112, Measured substance storage space 10
Even when the fluid to be measured flowing through 4 contains an organic substance, the organic substance is decomposed by the photocatalytic activity. Is prevented from adhering or being adsorbed on the electrode surface. Therefore, periodic cleaning of the electrode surface is not required, and the electrical conductivity can always be stably measured with high accuracy even without cleaning. In addition, high-precision measurement reproducibility is ensured.

If a surface of the glass plate 108 on the side of the substance-to-be-measured storage space 104 is coated with titanium oxide, the adhesion and adsorption of organic substances are also prevented on this surface side, and the organic matter in the substance-to-be-measured storage space 104 is prevented. Is also prevented, and good measurement accuracy is maintained.

Although the differential conductivity meter used in the phosphorus compound concentration measuring apparatus according to the present invention has been described in detail above, in the present invention, the above-described differential conductivity meter is used to measure the concentration of polycarboxylic acids. It is built into the measuring device. As described above, this differential conductivity meter can be configured to be used under light irradiation using an electrode whose surface is covered with a titanium oxide film, for example, and has a special differential measurement circuit. Therefore, a very small change in electric conductivity can be stably detected, particularly in a system having high electric conductivity and containing a water-soluble organic substance. The method and apparatus for measuring the concentration of polycarboxylic acids according to the present invention determine the concentration of polycarboxylic acids from the change in electric conductivity (increase in electric conductivity).

Conventionally, in a brine containing an organic substance, the electrode is largely soiled and stable measurement is almost impossible. However, as described above, the electrode surface is covered with a titanium oxide film and the titanium oxide is activated. By irradiating with light of about 350 nm, the electrode surface is very hydrophilic (a super-hydrophilic interface is formed) and has an oxidative decomposition property of an organic substance or the like due to photocatalytic activity. Does not adhere organic matter. In addition, since the hydration structure of the ions is not destroyed at the interface, it is extremely stable as compared with conventional electrode materials. In particular, an AC constant voltage drive and AC current amplification using three electrodes, and two electric conductivity cells are configured, and the difference measurement circuit between them is used to take advantage of the characteristics of the electrode material to achieve an ultra-high voltage near the ultimate. A highly sensitive and highly stable differential conductivity meter can be configured.

In the present invention, the sample is oxidized by the oxidizing means, and the increase in electric conductivity before and after the oxidation is measured with high accuracy and high sensitivity using the above-described differential conductivity meter. From the degree of increase, the concentration of the polycarboxylic acids is determined. There is no particular limitation on the method of measuring the increase in electrical conductivity caused by the oxidative decomposition of polycarboxylic acids in the sample, and the sample is continuously introduced into the oxidizing means, and the electrical conductivity before and after oxidation of the sample is continuously measured. A method of measuring the amount of increase in electric conductivity, a method of injecting a sample into a carrier liquid, introducing the sample into an oxidizing means, and measuring the amount of increase in electric conductivity can be used. As a particularly preferred method, there is a method in which a standard solution adjusted to the electric conductivity of a sample is used as a carrier liquid, and the sample is injected into the carrier liquid to continuously measure oxidative decomposition and the increase in electric conductivity. . According to this method, the measurement sensitivity of the difference conductivity meter, which is the detection device used in the present invention, can be further increased, which is advantageous for high-sensitivity measurement.

FIG. 9 shows an example of the apparatus for measuring the concentration of polycarboxylic acids according to the present invention using the above-described differential conductivity meter. A polycarboxylic acid concentration measuring apparatus 200 shown in FIG.
Is configured as a system that uses a standard solution according to the electrical conductivity of a sample as a carrier solution. Bottle 201
A standard liquid 202 as a carrier liquid is stored therein, and the carrier liquid is supplied to a sample injection valve 205 by a pump 204 via a degasser 203. The sample injection valve 205 quantifies the supplied carrier liquid as it is, or
The sample supplied from is diluted with the carrier liquid and quantified, and supplied to the sample measurement channel 208 via the degasser 207. The differential conductivity meter 209 as described above is arranged in the sample measurement channel 208. Difference conductivity meter 209
Has two electric conductivity measuring cells 210 and 211 (channels CH1 and ch2),
A time delay column 212 having a predetermined capacity is interposed between 10 and 211. The time delay column 212 is constituted by an oxidizing means filled and fixed with a photocatalyst carrier, for example, as described above.
The sample fluid flowing through the sample 8 is oxidized.
From the amplifier 213 of the difference conductivity meter 209, as described above, a signal of the difference between the detection signals from the two conductivity measurement cells 210 and 211, that is, the two conductivity measurement cells 21
The electrical conductivity difference signal between the positions 0 and 211 is output with high accuracy as a signal corresponding to the electrical conductivity increase during this time.

Here, the degassers 203 and 207 are provided particularly for stabilizing the differential conductivity meter 209. In other words, it is used to prevent fluctuation of electric conductivity due to passage of micro bubbles. Time delay column 212
Is a column for detecting a change in electric conductivity with time, if the liquid is sent at a constant flow rate with a constant volume and length, the conductivity at constant time intervals is defined as the difference between the electric conductivity of ch1 and ch2. Can be detected.

When only the standard solution as the carrier liquid is flowing through the sample measurement channel 208, the change in the electric conductivity as the base without the sample to be measured can be measured. In the case where the sample is injected and supplied to the sample measurement channel 208 together with the carrier liquid, the amount of increase in electric conductivity by the injected sample can be measured.

As described above, the difference in electrical conductivity between the positions of the electrical conductivity measuring cells 210 and 211 is measured with high accuracy by the differential conductivity meter 209. The characteristics of the increase in electric conductivity based on the oxidative decomposition of the polycarboxylic acids in this sample are as shown in FIGS. 10 and 11, for example. If the concentration of the polycarboxylic acid in the sample measurement flow path 208 changes continuously due to the injected sample, the time derivative of the polycarboxylic acid concentration changes as shown in FIG. One minute is detected as one peak. On the other hand, when a transient change occurs in the concentration of the polycarboxylic acid, the change in the concentration of the polycarboxylic acid is detected as an electric conductivity change as an overshoot waveform as shown in FIG. When using a conventional conductivity meter, if the conductivity of the base of the sample is extremely large, it is impossible to detect such a change in conductivity corresponding to such a small concentration of polycarboxylic acids. It is.
In the present invention, by using the differential conductivity meter 209 as described above, a minute increase in electrical conductivity due to oxidative decomposition of the polycarboxylic acids is quickly measured with high accuracy, high sensitivity, and thereby, the The concentration is determined with extremely high precision and sensitivity.

Next, more specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, as a sample, a sample obtained from a target system such as an aqueous system is used as it is as a sample,
There are various cases, such as a case where a sample sampled from such a target system is diluted with a solvent such as water at a certain dilution ratio, and a solution is used as the sample.

The measurement conditions for detecting polycarboxylic acids by the method of the present invention are not particularly limited, and include measurement temperature, pH, ion concentration in the sample, polycarboxylic acid concentration in the sample, supply rate of the sample, In the case of using an oxidizing means using a photocatalyst carrier, the light irradiation intensity, the light irradiation time, the type and concentration of the coexisting oxidizing agent, and the like can be arbitrarily set. However, the detection sensitivity of polycarboxylic acids depends on the measurement temperature, p
H, the supply speed of the sample, the light irradiation intensity, the light irradiation time, and the type and concentration of the coexisting oxidizing agent are affected, so that it is preferable to perform the measurement under certain measurement conditions. Preferred measurement conditions include the following conditions. Temperature: 10 to 70 ° C pH: 3 to 9 Light irradiation intensity: 1 to 100 W Light irradiation time: 20 to 200 seconds Type of coexisting oxidant: oxygen, hydrogen peroxide, ozone Concentration of coexisting oxidant: 0.01 to 100 Mmol / L

Next, a system of an apparatus for implementing the measuring method of the present invention will be described. As described above, the apparatus basically includes a pump for sending a carrier solution, an injector (injection valve) for injecting a sample solution containing polycarboxylic acids into the carrier solution, and an oxidation reactor (oxidizing means) for oxidizing the polycarboxylic acids. ), A differential conductivity meter for measuring electrical conductivity before and after oxidation, and a data processor for recording data measured by the differential conductivity meter. However, in some cases, the sample solution itself containing the polycarboxylic acid is continuously supplied and the carrier solution is not used, so that such a system does not require an injector.

The data processor preferably includes a calibration curve of the amount of increase in electric conductivity versus the concentration of the polycarboxylic acid, which is obtained in advance, and can perform arithmetic processing such as calculation of the concentration of the polycarboxylic acid. It is preferable that the control signal can be output to pumps such as a pump for supplying a solution containing a polycarboxylic acid in accordance with the above.

Note that, in addition to the above system, a degasser for suppressing the formation of bubbles on the electrode surface of the differential conductivity meter, and a mixing device such as an in-line mixer or a mixing coil for uniformly mixing the sample and the carrier liquid. A vessel or the like may be installed as needed.

More specifically, a measuring method and apparatus according to the present invention will be described with reference to FIG. FIG. 12 is an example of an apparatus for performing the measurement method of the present invention. A sample containing a certain amount of polycarboxylic acids is injected from the injector 301 into the carrier liquid. The carrier liquid containing this sample is oxidized by a pump 302 into an oxidizer 304 (oxidation reactor).
Is supplied to the position of one of the conductivity measuring cells 303 of the difference conductivity meter 306 installed immediately before. Here, the carrier liquid containing the sample whose electric conductivity before oxidation is measured is continuously oxidized by the oxidizing device 304 and supplied to the position of the other electric conductivity measuring cell 305 of the differential conductivity meter 306. .
The difference conductivity meter 306 measures the amount of increase (change) from the electric conductivity before oxidation to the electric conductivity after oxidation, is recorded in the data processor 307, and based on the amount of increase in electric conductivity, the polycarbonate is measured. The acid concentration is determined.

By using the method and apparatus of the present invention, polycarboxylic acids can be easily detected with high sensitivity and in a wide quantitative range. Further, the method of the present invention has a high response speed, and particularly, a continuous flow analysis method (FIA: Flow).
Application development as a highly sensitive detection method in a fully automatic continuous measurement system represented by Injection Analysis is possible.

Accordingly, the method of the present invention can be applied to various water treatment systems represented by a cooling water treatment system, a boiler water treatment system, and a wastewater treatment system. In addition to the water treatment system, the method of the present invention can be applied to any system to which a polycarboxylic acid is added. Specific examples of such applications include quantitative analysis of polycarboxylic acids used as retention and drainage improvers as paper and pulp manufacturing process chemicals, and thickeners and stabilizers in paints, emulsions, and latexes Analysis of polycarboxylic acid used as a material, improver of workability of fiber wall material, pesticide spreader, cosmetics, feed binder, resin processing binder, detergent builder, seed spray topsoil stabilizer, etc. Quantitative analysis of the polycarboxylic acid used in the above.

[0067]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, however, illustrate some embodiments of the present invention and do not limit the present invention in any way. L represents liter.

Reference Example 1 A production example of the photocatalyst carrier used in the examples is shown below. A 1 mm-diameter polymer granule composed of linear low-density polyethylene pellets (trade name “Nipolon L-M65”, manufactured by Tosoh Corporation, specific gravity 0.92) was prepared by an underwater cut method. 300 g of the polymer granules,
Titanium dioxide powder having photocatalytic activity (manufactured by Nippon Aerosil Co., Ltd., trade name "P-25", crystal form: anatase)
18.4 g was placed in a 1-liter eggplant-shaped flask and set in a stirring device of an evaporator capable of rotating and stirring, and preliminarily stirred so as to be uniformly mixed. Thereafter, the flask was heated to 185 ° C. in an oil bath while rotating, and the photocatalyst particles were thermally fused to the surface of the polymer particles. Since almost all of the charged titanium dioxide particles were supported on the polymer particles, the content of the photocatalyst particles in the photocatalyst carrier was about 6%.
% By weight.

Example 1 Polycarboxylic acids were detected using the apparatus shown in FIG. As the oxidation reactor 304 (oxidizing means) in FIG. 12, the photocatalyst carrier produced in Reference Example 1 was filled in a Teflon tube having an inner diameter of 2 mm and a length of 40 cm, and was spirally wound around a black light (40 W). What was installed in was used.

As a sample, an acrylic acid homopolymer (molecular weight: 4500) was diluted with pure water to a concentration shown in Table 1, and injected into the carrier solution from the injector 3 by 200 μL. Further, as the carrier liquid, a solution prepared by adding hydrogen peroxide to pure water at a concentration of 10 mmol / L was used, and 1.0 ml / min. Was sent. Table 1 shows the results.

[0071]

[Table 1]

Example 2 As a sample, an acrylic acid homopolymer (molecular weight: 4500)
Was diluted with concentrated water (electric conductivity of 400 μS / cm) obtained by concentrating industrial water five-fold, and sulfuric acid was added to pure water as a carrier liquid to obtain an electric conductivity of 400 μS / cm.
And an acrylic acid homopolymer was detected in the same manner as in Example 1 except that hydrogen peroxide was added so as to be 10 mmol / L. Table 2 shows the results.

[0073]

[Table 2]

As is clear from the above examples, polycarboxylic acids can be measured with extremely high sensitivity by using the method of the present invention. Furthermore, from Example 2, even a polycarboxylic acid present in a sample having a high ion concentration can be measured with high sensitivity by using the method of the present invention.

[0075]

As is clear from the above description, according to the present invention, since polycarboxylic acids can be measured with extremely high sensitivity and reproducibility, the present invention can be used in a wide range of applications to which polycarboxylic acids are added. Application is possible.
In addition, the method of the present invention can be applied to a fully automatic continuous measurement system using a continuous flow analysis method that has recently attracted attention.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a configuration example of a differential conductivity meter used in a polycarboxylic acid concentration measuring device according to the present invention.

FIG. 2 is a schematic circuit diagram showing another configuration example of the differential conductivity meter used in the concentration measuring device for polycarboxylic acids according to the present invention.

FIG. 3 is a schematic configuration diagram showing an example of use of a differential conductivity meter having a time delay column and used in the apparatus for measuring the concentration of polycarboxylic acids according to the present invention.

FIG. 4 is a schematic configuration diagram showing an example of an electric conductivity measurement cell that can be used in a differential conductivity meter according to the present invention.

FIG. 5 is a schematic configuration diagram showing another example of an electric conductivity measurement cell that can be used for a differential conductivity meter according to the present invention.

FIG. 6 is a schematic configuration diagram showing still another example of an electric conductivity measurement cell that can be used for a differential conductivity meter according to the present invention.

FIG. 7 is an exploded perspective view showing an example of a mechanical configuration of an electric conductivity measurement cell that can be used in a differential conductivity meter according to the present invention.

FIG. 8 is a perspective view showing a configuration example of an electrode of an electric conductivity measurement cell that can be used in a differential conductivity meter according to the present invention.

FIG. 9 is a schematic configuration diagram showing an example of a polycarboxylic acid concentration measuring device according to the present invention.

FIG. 10 is a characteristic diagram of a change in electric conductivity in the device of FIG. 9;

FIG. 11 is a characteristic diagram of another change in electric conductivity in the apparatus of FIG. 9;

FIG. 12 is a block diagram showing an example of an apparatus for implementing the present invention.

[Explanation of symbols]

 1,11 Differential conductivity meter 2,14 AC oscillator 3,4,12,13 Electric conductivity measurement cell 5 Magnification setting device 6,15 Phase inversion amplifier 7,9,16,21 Amplifier 8,17 Measurement range switch 10 , 22 Output 12a, 13a Current supply electrode 12b, 13b Electric conductivity detection electrode 18 Temperature compensator 19 Synchronous rectifier 20 Range adjuster 51 Differential conductivity meter 52 Flowing water pipe 53 Upstream position 54 Venturi tube 55, 57 Electricity Conductivity measuring cell 56 Time delay column 58 Downstream position 61, 71, 81 Electrical conductivity measuring cell 62, 72, 82 Measurement tube 63, 73, 83 Fluid to be measured 64 Power supply electrode 65, 74, 84 Electrical conductivity detection Electrodes for 66, 77, 87 Amplifiers 75, 76, 85 Electrodes for AC current supply 86 Ground electrode 91 Electric conductivity measuring cell 92 Electricity Main body 93 Titanium oxide layer 94 Electrode for measuring electric conductivity 94a, 94b Electrode for supplying alternating current 94c Electrode for detecting electric conductivity 95 Electrode holder 96 Substrate 97 Inflow 98 Outflow 99, 100, 101, 102 Flow holes 103, 105 Internal passage 104 Substance storage space 106a, 106b, 106c Through hole 107 Packing 108 Transparent glass plate as light transmitting body 109 Bolt 110 Cover body 111 Light transmitting window 112 Light irradiating means 200 Polycarboxylic acid concentration measuring device 201 Bottle 202 Standard solution 203, 207 Degasser 204 Pump 205 Injection valve 206 Sample injection system 208 Sample measurement flow path 209 Differential conductivity meter 210, 211 Electrical conductivity measurement cell 212 Time delay column (oxidizing means) 213 Amplifier 301 Njekuta 302 pumps 303 and 305 electric conductivity measuring cell 304 oxidation reactor (oxidation means) 306 Sa conductivity meter 307 data processor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirohito Higo 1-28 Shinsuna, Koto-ku, Tokyo Organo Corporation F-term (reference) 2G060 AA06 AC10 AE17 AE21 AF08 FA15 HC06

Claims (4)

[Claims] 1. A method comprising oxidizing a sample containing polycarboxylic acids,
The difference between the electrical conductivity of the sample before oxidation and the electrical conductivity after oxidation is determined by arranging an electrical conductivity measuring cell having at least two electrodes at the position before oxidation and the position after oxidation. Oxidative degradation of polycarboxylic acids by detecting the difference in the detection signal itself from the conductivity measurement cell using a difference conductivity meter that outputs the difference in the conductivity of the sample between the positions of the two conductivity measurement cells A method for measuring the concentration of polycarboxylic acids, comprising: measuring an increase in electric conductivity caused by the above method, and quantifying the concentration of polycarboxylic acid in the sample from the increase in electric conductivity. 2. The method according to claim 1, wherein a solid oxidant having a photocatalyst immobilized on a carrier is used as the oxidant of the sample, and the sample is oxidized by irradiating light with the oxidant in contact with the sample. The method for measuring the concentration of polycarboxylic acids according to claim 1. 3. The method of measuring an increase in electric conductivity, comprising:
Using a standard solution according to the electrical conductivity of the sample as a carrier liquid, continuously oxidizing the sample by injecting the sample into the carrier liquid, and continuously measuring the increase in electrical conductivity. The method for measuring the concentration of a polycarboxylic acid according to claim 1, wherein the method is characterized in that: 4. A sample measurement flow path through which a sample containing polycarboxylic acids flows, oxidizing means for the sample disposed in the sample measurement flow path, and upstream and downstream sides of the sample oxidizing means. In addition, an electric conductivity measurement cell having at least two electrodes is provided, and a difference between detection signals themselves from both electric conductivity measurement cells is output as a difference in electric conductivity of the sample between the positions of both electric conductivity measurement cells. Measuring the amount of increase in electric conductivity caused by oxidative decomposition of polycarboxylic acids from the output of the difference conductometer, and calculating the amount of polycarboxylic acid in the sample from the increase in electric conductivity. A concentration measuring device for polycarboxylic acids, wherein the concentration is determined.