JPS6248192B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for measuring oxidizable substances, and more specifically, it provides a rapid and simple flow-type measuring method for oxidizable substances in water quality, and thereby provides a method for measuring and analyzing oxidizable substances in water quality. The present invention relates to a method of providing a device useful for inspection, monitoring, etc. In recent years, organic water pollutants, inorganic and/or organic reducing substances, or oxidizable substances under specific conditions, are present in various wastewaters such as urban sewage, human waste, domestic wastewater, and industrial wastewater that are generated as people become more sophisticated in their daily lives. There is a long-awaited need for a quick, simple, and automatable method for measuring substances that exhibit sexual activity. This measurement method is not limited to the above-mentioned oxidizable substances, but also applies to oxidizable substances in natural waters such as river water, lake water, hot spring water, sea water, etc. It is well known that this is a long-awaited product from the viewpoint of plant flourishing. As described above, there are many other examples of the existence of various inorganic and/or organic oxidizable substances as products of natural and industrial activities. Regarding the measurement method of such oxidizable substances, please refer to Japanese Industrial Standards (JIS), Environmental Agency notification, bottom sediment investigation method,
Measurement methods based on food testing methods, sanitary testing methods, agricultural chemical experiment methods, sewage laws, water supply laws, etc. are in place, and the latest chemical analysis methods and instrumental analysis methods are being introduced from time to time. There is. The measurement methods are becoming more precise, faster, and simpler by making full use of the latest analysis and measurement technology, while the automation of the measurement devices is rapidly increasing due to the demands of the times, such as labor-saving measurement and continuous monitoring. are doing. In particular, with regard to organic water pollutants, the total amount of chemical oxygen demand (COD) regulations implemented in wide-area closed water areas such as the Seto Inland Sea, Tokyo Bay, and Ise Bay began in June 1980, and COD automatic The installation of measuring equipment is now mandatory. As the automatic COD measurement device, an automatic device using a timer has been developed in accordance with JIS-K0102 (1974), but since this device uses a batch operation method, Even if we attempt to automate the process by incorporating numerous time-limiting devices, we cannot expect dramatic results because it merely converts human operations into mechanical operations. Moreover, the device itself is very expensive, has a complicated mechanism, and has many drawbacks such as troublesome maintenance and high repair costs. Furthermore, the measurement speed of this device is one sample per hour, which is JIS-1.
Based on the K0102 factory wastewater test method, the speed is the same as when measuring oxygen consumption (COD) by potassium permanganate at 100℃ by manual analysis, so there is no particular advantage, and the official method is currently used. However, considering that this is only a manual analysis method, the above
It must be said that the industrial value of automatic COD measurement equipment is lacking. It is well known that similar facts are also pointed out regarding other methods of measuring oxidizable substances. That is, the main object of the present invention is to provide a novel flow-type measurement method for analyzing oxidizable substances. An object of the present invention is to cause a redox reaction to occur by causing a specific oxidizing substance to act on an oxidizable substance under specific reaction conditions in a pipe, and to advantageously measure the oxidizable substance. The purpose is to provide a method. Other objects of the present invention will become apparent from the following description. Such a measurement method according to the present invention involves continuously introducing a small amount of a sample containing an oxidizable substance at arbitrary injection intervals into a flowing liquid in a tube containing an oxidizing substance, and promoting the process by mixing and heating. Since this is a flow measurement technology that is achieved by continuously detecting the amount of reaction products obtained as a result of the redox reaction, it is possible to detect organic water pollutants, inorganic and/or organic reducing substances. It is extremely suitable for measuring substances, or substances that exhibit oxidizability under specific conditions (generally referred to as oxidizable substances). In addition, in this measurement method, a solution containing an oxidizing substance is continuously passed through a thin tube with an inner diameter of 2 mm or less using a pump, and a sample containing an oxidizable substance is introduced into the solution through a direct or indirect flow path. It is an automatic and mechanical method in which the reactants are intermittently injected at arbitrary or fixed time intervals, the substances undergo redox reactions with each other through mixed transport within the tube, and then the reactants are continuously detected. It has excellent analytical precision and repeatability.
That is, in order to achieve the flow measurement method of the present invention, components such as a liquid delivery device, a detection device, a recording device, a thin tube, etc. are essential, as well as a sample introduction device, joints, filters, syringes, etc. It is essential. Further, a constant temperature device and the like for appropriately accelerating or decelerating the reaction within the capillary are also important components. If a measuring device based on the present invention is manufactured by appropriately combining the above-mentioned components, a solution containing an oxidizing substance can be continuously flowed into the capillary by a liquid feeding device, and the oxidizable substance can be removed. The sample solution contained in the solution is intermittently introduced directly or indirectly into the oxidizing substance-containing solution through a sample introduction device, and the tube portion downstream of this introduction part is heated to interact with the oxidizing substance in the liquid. The present invention can be achieved by promoting the reaction with an oxidizing substance, detecting the amount of the reaction product using an appropriate detection device, and continuously recording the obtained signal using a recording device. It becomes possible to achieve the purpose easily. Furthermore, the present invention has made it possible to measure oxidizable substances using a flow-through method, which had previously been analyzed only based on measurement methods that utilize batch-type operations; Commercially available COD manufactured and commercialized in accordance with the formula operation method
When measuring the content of oxidizable substances in water as COD using an automatic measuring device, analysis could only be performed once an hour, but the flow-type measuring method according to the present invention Taking into account that if this method is adopted, it will be possible to measure oxidizable substances at least several dozen times per hour.
This significantly increases its industrial and social significance. In particular, the measuring device based on the present invention measures water quality.
Considering that organic water pollutants can be labeled as oxidizable substances by oxidizing substances such as potassium permanganate and potassium dichromate under the total amount of COD control, eutrophic red tide occurrence in closed water bodies, aquatic plants, etc. It is easy to imagine that there is an extremely large possibility that this measuring device can be used as a powerful continuous water quality monitoring device in solving social problems related to the water quality environment such as overgrowth. Here, the oxidizable substances referred to in the present invention refer to organic water pollutants in urban sewage, human waste, domestic wastewater, industrial wastewater, natural water, etc., and inorganic and/or organic cyclic substances in aqueous media. It is also a general term for substances used in daily life and/or industry that exhibit oxidizability under specific conditions (for example, in the presence of strong oxidizing agents). In addition, as the oxidizing substances used in the present invention, in view of the fact that the thin tube (reaction tube part) is heated to promote the reaction as described above, generally unstable substances, especially thermally unstable substances, should be avoided. Furthermore, when spectrophotometry is used to measure the production system or reaction system, it is desirable that the substance is colored and becomes colorless or a different color when reduced. From this point of view, the oxidizing substances of the present invention include chromates such as sodium chromate and potassium chromate, dichromates such as sodium dichromate, potassium dichromate, and ammonium dichromate, and peroxide. Contains permanganates such as sodium manganate and potassium permanganate, ceric salts such as ceric sulfate and ceric nitrate, and halogens such as iodine, bromine, chlorine, potassium iodate, and potassium iodide. oxidizing agent, or a substance generally known as an oxidizing agent such as hydrogen peroxide and its salts, ozone, persulfate, or a substance that has a redox potential 0.2 to 0.4 V higher than the above-mentioned oxidizable substances. . Furthermore, the reaction between the oxidizable substance and the oxidizing substance in the tube in the present invention can be carried out at any hydrogen ion concentration (PH). That is, it is mainly based on a redox reaction between the substances, and is based on acids such as sulfuric acid, phosphoric acid, carbonic acid, and/or bases such as ammonia, sodium hydroxide, potassium hydroxide, magnesium hydroxide, or the acid and the The reaction can be carried out in any aqueous system containing a base salt or the like at any concentration. In addition,
The reaction can also be carried out in non-aqueous solvent systems. The amount of reaction products generated in the tube due to such redox reactions can be determined by ordinary instrumental analysis such as absorption spectrometry, fluorescence analysis, electrochemical analysis, atomic absorption spectrometry, and chromatography. It is possible to detect with high sensitivity and high selectivity by method and/or analytical chemical method, and it is also possible to detect by physical method such as potentiometric method. Furthermore, in order to effectively measure oxidizable substances in the present invention, the solution containing the oxidizing substance is continuously passed through the pipe, and the solution containing the oxidizable substance is passed directly or separately into the flowing liquid. It is essential to introduce the sample solution containing the oxidizable substance indirectly via the tube. Ready-made peristaltic type (peristaltic type) and/or
Alternatively, piston-type (reciprocating) pumps and plunger-type high-pressure constant-flow pumps for high-performance liquid chromatographs can be used. It is also possible to place the liquid in the tube and use the difference in gravity to pass the liquid into the tube. The above pumps can be used alone or in combination, but because they pump solutions containing corrosive substances such as oxidizing substances, acids, bases, and salts, the wetted parts are marked with the registered trademark "Teflon".
Tetrafluoroethylene polymer (hereinafter referred to as ``Teflon''), which is well known as ``Teflon'', corrosion-resistant polymer products such as polypropylene, ceramics, sapphire,
It is preferable to use one made of a corrosion-resistant material such as ruby. The tubes for passing oxidizing substance-containing solutions, etc., include ready-made Teflon tubes with various diameters and lengths, polyethylene tubes, silicone tubes, polyvinyl chloride tubes known as the registered trademark "Tygon," stainless steel tubes, etc. Metal tubes, glass tubes including capillary tubes, etc. can be used, but it is necessary to select a tube made of a suitable material depending on the target substance to be sent. Furthermore, in order to prevent diffusion of the introduced sample solution as it moves within the tube, it is preferable to use a tube as thin as possible, and the inner diameter of the tube should be 2 mm or less. The reason why the inner diameter is set to 2 mm or less is that as long as the pipe has a length sufficient to allow the oxidation product-containing solution and the sample solution to come into contact and react with each other, the inner diameter of 2 mm or less is effective. This is because preferable reaction conditions can be obtained due to the pressure loss, that is, high pressure inside the tube. The length of the pipe must also be selected appropriately depending on the mutual reaction rate of the oxidizing substance and the oxidizable substance, and if the pipe length, flow rate, etc. are adjusted appropriately, the length can be selected according to the reactivity of each oxidizable substance. It turned out that it is also possible to measure individual oxidizable substances. The common method for introducing a sample solution containing an oxidizable substance is to use a ready-made sample injector and inject it with a syringe through a septum rubber. Since individual differences in the process can be ignored, favorable results can be obtained in terms of analysis accuracy, repeatability, etc. Although it is possible to introduce the sample directly into the oxidizing substance-containing solution, a separate branch pipe is used to feed a solution containing a pH buffer, a masking agent for interfering components, a reaction accelerator, etc. It was confirmed that an indirect introduction method in which the sample is introduced into the solution and then mixed with the oxidizing substance-containing solution using a ready-made mixing device such as a mixing joint also produces favorable results. Note that the oxidizing substance-containing solution mixed with the sample solution etc. generates a reaction product through an oxidation-reduction reaction in the above-mentioned tube which acts as a reactor. At this time, in order to accelerate or decelerate the reaction, it is also possible to heat or cool the tube from the outside using a constant temperature bath. Also,
External stimulation using an ultrasonic generator or the like to all or part of the reaction tube may also be effective in controlling the reaction and preventing contamination of the reaction tube with reaction products. . The interior of the tube becomes partially mixed due to the transfer of the contents, and the introduced sample solution causes a redox reaction by diffusion and mixing at the interface with the oxidizing substance-containing solution. At the same time, the reaction product is transported within the tube, and the amount of the reaction product is detected directly or indirectly by appropriately selecting the detection method described above. Reaction products are converted into electrical signals and recorded as peaks. As the recording device, a ready-made one-pen or multi-pen type recorder can be used, but a multi-range type recorder is preferable. In addition, automation can be achieved by processing the recorded data using a data processing device with a built-in microcomputer, and if used in conjunction with an automatic sample collection device, it can be used as an oxidizable substance measuring device using a completely automatic distribution method. It becomes possible to provide The industrial and social value of the present invention is to reduce organic water pollution in various wastewaters and natural waters, in order to put the flow-type oxidizable substance measuring device produced according to the measuring method into practical use. The most suitable explanation can be given when a substance is measured as an oxidizable substance. In other words, organic water pollutants present in various types of wastewater such as urban sewage, human waste, domestic wastewater, industrial wastewater, natural water such as river water, lake water, seawater, and processed water such as tap water and industrial water. For oxidizable substances, typical utility value can be found in cases where reactions are performed and measured using strong oxidizing substances such as potassium dichromate, potassium permanganate, and iodine. In addition, when these colored oxidizing substances with relatively strong oxidizing power are used, absorption spectrometry can be used as the most reliable detection method, as well as providing high sensitivity, stable, and rapid response performance. Therefore, it is possible to make the most effective use of the measurement performance of this measurement method, and the measured values obtained by the present invention for oxidizable substances are also the COD values of the manual analysis method according to JIS-K0102 (1974). It was found that the agreement was relatively good. As described above, according to the measuring method of the present invention, it can be used industrially to replace the conventional batch-operated oxidizable substance measuring device, which has not been able to significantly increase its utility value even when automated. It has become possible to provide a flow-type measuring device for oxidizable substances that has high utility value and has excellent measurement performance.
It can be said that its industrial and social significance is extremely high. The examples described below are intended to better explain the invention and are not intended to limit the scope of the invention in any way. Furthermore, unless otherwise specified, all parts and percentages shown in Examples are expressed on a volume basis, and parts per million (ppm) are expressed on a weight basis. The measurement of organic pollutants in water described in the following examples is based on Japanese Industrial Standards (JIS) KO102.
(1974) Item 13, oxidizable substances in the water are expressed as oxygen consumption (COD) by potassium permanganate at 100℃, which indicates the amount of oxygen consumed by organic matter. It is considered that quantity is the main proportion. Basic Experiment First, a measurement method was carried out in which the thin tube was not heated in the configuration shown in FIG. This means that even if "heating", which is a requirement of the present invention, is not carried out, the function of the capillary allows for an effective reaction with good reproducibility (however, "heating" does not shorten the reaction time too much). )It is shown that. The operation was carried out using a 0.27mM potassium permanganate solution 1 dissolved in 3.3% sulfuric acid using a Kyowa Seimitsu KHU-52 single plunger micropump 2.
The liquid is continuously fed into a Teflon tube with an inner diameter of 0.5 mm and a length of 10 m at a flow rate of 1.9 ml/min, and the sample is injected from the sample injector 3 installed in the middle of the Teflon tube through the septum rubber using a microsyringe. Inject 20μ of the solution. At room temperature (approximately 30°C), potassium permanganate as an oxidizing substance and the oxidizable substance in the sample are reacted in the Teflon tube 4, and the reactant is transported at the same time.It is equipped with a flow cell with an optical path length of 10 mm. Shimadzu UV-100-01
Using a type spectrophotometer 5, the amount of reactant is detected indirectly from the decrease in the absorbance of potassium permanganate at a wavelength of 525 nm. The obtained absorbance change is continuously recorded using a Hitachi model 056 multi-range recorder 6, and the oxidizable substance is measured from the peak.
Figure 2 shows the results when a solution containing sodium oxalate as an oxidizable substance with a COD value of 21 to 170 ppm as described in JIS-KO102 (1974) was used as a sample. In Figure 2, the next sample was injected after the peak had finished, but at a flow rate of 1.9 ml/min, if the injection interval was set to 30 seconds, it would take 1 hour.
120 measurements are possible. With this measurement method,
Oxidizable substances in wastewater, including photographic developer waste, are
When measured using the calibration curve obtained from the figure,
A COD value of 110 p.pm was obtained. In addition,
When the wastewater was manually analyzed based on JIS-KO102, the COD value was 130 p.pm. Example 1 In order to apply the measurement method of the present invention to the measurement of organic pollutants in various wastewaters, an apparatus was prototyped with the configuration shown in FIG. 3. In order to maximize the performance of the device, a dual pump was used in the design. 0.49mM potassium permanganate 1
1 solution and 6.7% sulfuric acid solution 12 are separated into 2 parts of potassium permanganate solution through a solution filter 13 and an air bleeder 15 using a Kyowa Seimitsu KHU-W-104 double plunger type high-pressure constant flow micropump 16. 1 part of the sulfuric acid solution is continuously passed through each Teflon tube. The potassium permanganate solution is sent to the mixing joint 20 through a line filter 17, while the sulfuric acid solution is sent to the mixing joint 20 through a constant volume sampling valve 19 made by Kusano Kagaku after passing through the line filter 17. and mixed with potassium permanganate solution. The sample solution is injected into the sulfuric acid solution through the aforementioned sampling valve 19 with a capacity of 20 μm using a valve injection syringe with a capacity of 500 μm, and then mixed in the mixing joint 20. The mixed content liquid is the inner diameter of the pipe.
The liquid is transported in a Teflon tube with a diameter of 0.5 mm and a tube length of 40 m at a rate of approximately 1.0 ml per minute. Teflon tube 21,
By immersing it in the boiling water bath 22 and heating it, the reaction between the potassium permanganate in the content and the oxidizable substance is accelerated. The absorbance decrease of purple potassium permanganate accompanying the reaction was measured at 525 nm using a Shimadzu UV-100-01 spectrophotometer 23 equipped with a quartz flow cell with an optical path length of 10 mm and an internal volume of 18 μ.
Detect with. The obtained signal was continuously recorded using a Shimadzu model R-11 recorder 24 modified to have a multi-range function, and the oxidizable substances were indirectly detected from the peak height.
Measurements are taken at a rate of approximately 30 times per hour. Spectrophotometer 23
The liquid outlet is connected to a Teflon thin tube 25 with an inner diameter of 0.25 mm, which further enhances the effect of pressure loss due to the tube flow path. In this example, glucose was used as an indicator substance for organic water pollutants, and as a result of a detailed study of the device conditions and operating conditions of the above-mentioned measuring device, the method for measuring oxidizable substances as described above was found. I got it. Further, as a preferable feature of the measurement method,
In COD measurement according to JIS-KO102 (1974), it was necessary to add a large amount (approximately 1 g) of silver sulfate to suppress interfering chloride ions, but with this method, 7000 p.pm The coexistence of chloride ions does not interfere with the measurement of oxidizable substances, and the presence level of chloride ions in seawater is
Even at 19,000 p.pm, it only gives an error of about 10% to the measured value of oxidizable substances. Note that this is considered to be due to the difference in reaction rate between the organic substance and chloride ion with respect to potassium permanganate. Based on the results of these studies, we decided to use glucose as an indicator of oxidizable substances.
JIS-KO102 of glucose solutions of various concentrations on the horizontal axis
When we created a calibration curve by taking the COD value according to the method and plotting the peak height on the vertical axis, we succeeded in obtaining a linear calibration curve in the range of 0 to 200 p.pm as the COD value according to the JIS method. Since this measurement method automatically performs the reaction within the device, it has good repeatability and the analysis accuracy is extremely high, with a coefficient of variation of approximately 0.5% when averaging 10 measurements. Using this measurement method, the amount of oxidizable substances in various wastewaters was measured as COD using the aforementioned calibration curve, and the COD value obtained by manually analyzing the wastewater based on JIS-KO102 (1974) was calculated. Also listed in Table 1. the result,
As is clear from the X/Y ratio in Table 1, it has been confirmed that the measured values by the flow-type oxidizable substance measuring method specified in the present invention match the JIS method COD values within the tolerance range of approximately ±30%. It was done.

[Table] Example 2 For the measuring device used in Example 1,
0.68mM potassium permanganate solution and 0.1% by weight
If 1 part of each of 40% phosphoric acid solution containing silver nitrate is delivered and the flow rate after mixing at mixing joint 20 is approximately 1.0 ml/min, the inner diameter to be used is 0.5 mm. The suitable length of the Teflon tube 21 was 30 m. This is considered to be because the added silver acted as a catalyst for the redox reaction. In addition,
In this example, it was confirmed that the measured value of the oxidizable substance obtained using glucose as an indicator substance agreed fairly well with the COD value determined by the JIS method, as in the case of Example 2. It was also possible to use a mixed acid solution containing 6% sulfuric acid and 4% phosphoric acid instead of the 40% phosphoric acid solution. Example 3 Regarding the measuring device used in the basic experiment,
A 1.2mM potassium dichromate solution dissolved in 33% sulfuric acid was passed through the Teflon tube 4 with an inner diameter of 0.5mm at a flow rate of approximately 0.8ml/min.
When measuring oxidizable substances from the decrease in absorbance of potassium dichromate at 349 nm after heating to 100°C, the length of the Teflon tube 4 was required to be 50 m or more. In this example, milk sugar (lactose) was used as an indicator substance of an oxidizable substance, and as in the case of glucose, a calibration curve was successfully obtained from the JIS method COD value and peak height. Furthermore, it has been found that it is also possible to detect chromium () ions produced as a result of the above reaction at 600 nm and create a calibration curve. Similarly, for the measuring device used in the basic experiment,
The same operation as above was performed using a 0.4 mM potassium dichromate solution, and it was also possible to obtain a peak due to the oxidizable substance from the change in absorbance of potassium chromate at 366 nm. As verified in the examples described above, the method of the present invention makes it possible to measure oxidizable substances with excellent reproducibility and analytical accuracy over a wide COD measurement range of 1 to 200 ppm. especially,
Such stable and accurate measurements are achieved by using a tube with a narrow inner diameter of 2 mm or less as a reaction tube for this type of measurement, and by heating the tube. In other words, compared to tubes with an inner diameter of 5 mm or more that have been commonly used in this type of measurement field,
A high pressure that is inversely proportional to the fourth power of the inner diameter of the tube is applied in the tube below, so the contact surface of the sample solution introduced into the oxidizing flowing liquid with the former is laminar flow, which is faster in the center, and the flow increases depending on the pressure. This is because the sharpened bullet-like shape allows the substances contained in both to effectively disperse and mix molecules with each other, thereby promoting the oxidation reaction.
Moreover, such high pressure inside the tube promotes the reaction, making it difficult for the internal solution to boil even if the tube is heated to over 100°C. It is highly effective in measuring slow oxidation reactions.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a basic experimental device in which a single pump is used to implement the measurement method of the present invention. In the figure, numeral 1 is a solution containing an oxidizing substance, 2 is a single plunger pump, and 3
4 indicates a sample injector, 4 a reaction tube using a Teflon tube with an inner diameter of 0.5 mm, 5 a spectrophotometer equipped with a flow cell, and 6 a recorder. Figure 2 shows the measurement results of oxidizable substances obtained in basic experiments. In the figure, curve a is JIS-
Sodium oxalate solution with COD value of 0 p.pm based on KO102 (1974), b is 21 p.pm, c is
43p.pm, d is 86p.pm, e is 130p.pm, f is
170 p.pm sodium oxalate solution respectively.
The peaks obtained by injecting 20μ each are shown. Further, in the figure, the symbol g indicates the initial injection position of the sample, and h indicates the residence time of the injected sample within the measuring device. FIG. 3 is a schematic diagram when a dual pump is employed as the device used in the measurement method of the present invention. In the figure, code 11 is an oxidizing substance-containing solution;
12 is a solution containing sulfuric acid, phosphoric acid, nitric acid, etc., 13 is a solution filter, 14 is a Teflon tube with an inner diameter of 2 mm, 15 is an air vent, 16 is a double plunger type pump, 17 is a line filter,
18 is a Teflon tube with an inner diameter of 0.5 mm, 19 is a sampling valve, 20 is a mixing joint, 2
1 is a reaction tube using a Teflon tube with an inner diameter of 0.5 mm;
22 is a hot water bath, 23 is a spectrophotometer equipped with a flow cell, 24 is a recorder, and 25 is a Teflon tube with an inner diameter of 0.25 mm.

Claims (1)

[Claims] 1. A solution containing a thermally stable oxidizing substance selected from the group consisting of chromates, dichromates, permanganates, ceric salts, or halogen-containing oxidizing agents. , while flowing through a thin tube with an inner diameter of 2 mm or less, intermittently introducing a sample solution containing an oxidizable substance into this oxidizing substance-containing solution, and heating the thin tube portion downstream from the introduction part, A flow-type oxidizable substance measuring method characterized by causing an oxidizing substance and an oxidizable substance in a liquid flowing through this portion to react with each other, and directly or indirectly detecting the amount of the substance produced thereby. 2. The method according to claim 1, wherein the inner diameter of the capillary is 0.5 mm, and the flow rate of the oxidizing substance-containing solution is 0.8 ml/min or more.