JPS6345063B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device for measuring ultratrace amounts of nitrogen by form,
Specifically, the present invention relates to a measuring device for separately quantifying ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and organic nitrogen.

BACKGROUND ART In recent years, the amount and components of nitrogen in environmental water such as rivers, lakes, marine areas, and wastewater such as industrial wastewater, process wastewater, and sanitary wastewater, which are said to cause eutrophication of water quality, have become a major problem. The forms of nitrogen contained in these waters are divided into four types: ammonia, nitrite, nitrate, and organic.
Understanding the content of nitrogen in each form is important for pollution control measures such as wastewater.

Conventionally, ultratrace nitrogen measurement devices for different forms are:
Two reaction tubes are provided, and in the first reaction tube, ammonia nitrogen in the sample water is reduced with a bromide ion-containing reaction solution using helium as a carrier gas, and the entrained moisture is completely removed, followed by gas chromatography. The nitrite nitrogen in the sample water is reduced to nitrogen gas using the amidosulfonic acid reaction solution in the second reaction tube, and the entrained moisture is completely removed, followed by quantitative determination using gas chromatography.
An apparatus has been proposed in which nitrate nitrogen is reduced to nitrite ions with zinc powder and then measured using the second method. However, with this device, dissolved nitrogen gas in each reaction solution and sample water must be completely removed, and entrained moisture must be completely removed even after reduction to nitrogen gas, so pretreatment operations are difficult. This method has the drawbacks of being time consuming and complicated to operate.

The present invention provides an apparatus for measuring ultra-trace amounts of nitrogen by form without such drawbacks, and the gist thereof is to provide an ultra-trace amount of nitrogen measuring device characterized by having the following measurement section, distillation section A, and distillation section B. Measuring device for each form.

(a) Measuring section A reaction section consisting of a cylindrical reaction tube filled with a reduction catalyst, which has a sample inlet and a hydrogen gas inlet at one end and a gas outlet at the other end.It has a gas inlet and a gas outlet. An acidic gas removal section filled with a solid alkaline substance inside the container; A heating section for heating the reaction section and the acidic gas removal section; A coulometric titration section having a gas inlet pipe, a gas outlet, an electrolytic electrode, an end point detection electrode, and an electrolytic tank. The reaction section and the acidic gas removal section are each housed in the heating section, the gas outlet of the reaction section is connected to the gas inlet of the acidic gas removal section, and the gas outlet of the acidic gas removal section is connected to the coulometric titration section. It is connected to a gas introduction pipe, and the gas introduction pipe is opened near the bottom inside the electrolytic cell.

(b) Distillation section A A distillation tank made of acid-resistant material and having a sample inlet, a carrier gas inlet pipe, and a generated gas outlet. It consists of a reflux condenser, and the carrier gas inlet pipe opens near the bottom of the distillation tank. The lower end of the reflux condenser is connected to the generated gas outlet of the distillation tank, and the upper end is connected near the sample inlet of the reaction section.

(c) Distillation section B A distillation tank made of an alkali-resistant material and having a sample inlet, a carrier gas inlet pipe, and a generated gas outlet. It consists of a reflux condenser, and the carrier gas inlet pipe opens near the bottom of the distillation tank. The lower end of the reflux condenser is connected to the generated gas outlet of the distillation tank, and the upper end is connected to the gas inlet pipe of the coulometric titration section.

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The present invention will be explained below with reference to the drawings. FIG. 1 is an explanatory diagram of an example of a device according to the present invention. 1 in the diagram
2 is a measurement section, 2 is a distillation section A, 3 is a control section, 4 is a distillation section B, 12 and 19 are a distillation tank, 23 is a coulometric titration section, 29 and 32 are a heating section, 30 is an acidic gas removal section, 33 is a This is the reaction part.

The measurement unit 1 includes a reaction unit 33 for reducing the nitrogen compound in the sample and converting it into ammonia, an acid gas removal unit 30 for removing acid gas from the converted gas, and a coulometric unit for quantifying ammonia. It is composed of a titration section 23.

The reaction section 33 has a cylindrical reaction tube having a sample inlet 5 and a hydrogen gas inlet tube 34 at one end and a gas outlet at the other end, and metal particles such as nickel or copper, pumice, alumina, etc. are placed inside the reaction tube. These are inert particles whose surfaces are coated with these metals and filled with metal catalysts. Although the size of the catalyst particles depends on the size of the reaction tube, catalyst particles of about 0.5 to 15 mm are usually used. The catalyst is preferably filled with a heat-resistant inert material such as quartz, asbestos, alumina, etc. mixed with catalyst particles. The reaction part 33 is housed in a heating part 32 such as an electric furnace with a built-in heating wire, and has a heating temperature of 300 to 600
It is maintained at a high temperature of about ℃.

The acidic gas removal section 30 is for removing acidic gases such as hydrogen sulfide contained in the gas discharged from the reaction section. It is filled with an alkali absorbent in which one or a mixture of two or more metal oxides or hydroxides is made into particles of about 1 to 7 mm. Specific examples of alkaline absorbents include a mixture of sodium hydroxide and calcium oxide (soda lime), a mixture of calcium hydroxide and calcium oxide, and a mixture of sodium hydroxide and
- Mixtures with alumina, mixtures of sodium hydroxide, potassium carbonate and asbestos, etc.

The acid gas removal section 30 is housed in a heating section 29 similar to the heating section 32, and is maintained at a temperature of about room temperature to 300°C.

The coulometric titration unit 23 is for quantifying ammonia in the gas discharged from the acidic gas removal unit, and includes an electrolytic tank 27 with a sliding lid, an electrolytic electrode 24 installed in the tank, a detection electrode 25, and a gas introduction unit. It is composed of pipes 22 and 26 and a gas outlet pipe 21. Each electrode 24,
25 and the gas introduction pipes 22 and 26 are installed at a position where their lower ends are submerged in the electrolyte.

The distillation section A2 is for expelling nitrite nitrogen in the sample as nitrogen monoxide or nitrogen dioxide gas, and includes a distillation tank 19 having a sample inlet 18, a carrier gas inlet pipe 17, and a generated gas outlet, and a reflux tank. It is composed of a condenser 7 and a heating section 20. The carrier gas introduction pipe 17 is opened near the bottom of the distillation tank 19, and it is preferable to attach a perforated plate to the open end. The distillation tank 19 contains 30 to 80 wt% of non-volatile strong acids such as sulfuric acid and phosphoric acid, preferably
Since a 30 to 50 wt% aqueous solution is contained, it is preferable to use an acid-resistant material such as glass, stainless steel, or ceramic. Reflux condenser 7
It is preferable to have an obstruction in the gas flow path so as to avoid volatilization of the mist, and a coiled pipe is usually used, but if it is a straight pipe, it may be used with a filler.

The lower end opening of the reflux condenser 7 is connected to the generated gas outlet of the distillation tank 19, and the upper end opening is connected to the vicinity of the sample inlet 5 of the reaction section 33 through the conduit 6. The distillation tank 19 is heated by a heater 20 to 70°C to the boiling temperature of the liquid, preferably 80 to 90°C.

Distillation part B4 is for expelling ammonia nitrogen in the sample as ammonia gas,
It is composed of a distillation tank 12 having a sample inlet 11, a carrier gas inlet pipe 10, and a generated gas outlet, a reflux condenser 9, and a heater 13. The carrier gas introduction pipe 10 is opened near the bottom of the distillation tank 12, and it is preferable to attach a perforated plate to the open end.

The distillation tank 12 contains 20 to 50 wt% of strong alkali such as sodium hydroxide or potassium hydroxide, preferably 20 wt%.
Since an aqueous solution of ~40 wt% is contained, it is preferable to use an alkali-resistant material such as high nickel alloy steel, ceramic, etc. The reflux condenser 9 is similar to the reflux condenser 7,
Its lower end opening is connected to the generated gas outlet of the distillation tank 12, and its upper end opening is connected to the gas introduction pipe 22 of the coulometric titration section 23 through a conduit 8. Distillation tank 12
is heated by the heater 13 to 70° C. to the boiling temperature of the liquid, preferably 100° C. to the boiling temperature of the liquid.

The control unit 3 usually includes a coulometric titration control device 14, a temperature control device 15, and a gas flow rate control device 16. The coulometric titration control device 14 amplifies the electric signal corresponding to the hydrogen ion concentration obtained from the detection electrode 25, converts it into a current output proportional to the deviation from the end point PH value, and sends the electrolytic signal to the electrolytic electrode 24. Current is supplied.

On the other hand, if necessary, this electrolytic current is calculated as a current by subtracting the blank current, and after performing correction calculations such as analysis value unit conversion and sampling amount coefficient to indicate the ratio to the collected sample, it is integrated, and the electrical quantity is It is displayed as a continuation value of the analysis commensurate with the above.

The temperature control device 15 is for adjusting the temperature of the heating sections 29, 32 and the heaters 13, 20 to a predetermined temperature.

The gas flow rate control device 16 controls hydrogen gas introduced from the hydrogen gas introduction pipe 34, hydrogen gas introduced from the carrier gas introduction pipes 10 and 17, nitrogen gas,
This is for adjusting the flow rate of carrier gas such as argon gas to a predetermined amount. The flow rate of these gases is usually 200-700ml/min, preferably 400-500ml/min.
Selected from the range of ml/min.

Next, a case will be described in which water containing an ultratrace amount of nitrogen compounds is analyzed using the apparatus of the present invention configured as described above. First, to measure the total nitrogen amount, a predetermined amount of sample water is injected from the sample inlet 5 of the measuring section 1. The injected sample water is accompanied by hydrogen gas introduced from the hydrogen gas introduction pipe 34, and all nitrogen compounds are reduced to ammonia in the reaction section 33. The generated ammonia gas is sent to the conduit 31 along with hydrogen gas.
The acid gas is introduced into the acid gas removal section 30, and the coexisting acid gas is removed. Then conduits 28 and 26
The sample is then introduced into the electrolytic cell 27, where it is absorbed by an electrolytic solution, such as a 1% aqueous sodium sulfate solution, which has been placed in advance in the electrolytic cell 27, and coulometric titration is performed.
The titration results are displayed on the coulometric titration control device 14.
The amount of sample water injected varies depending on the amount of nitrogen compounds contained, but is usually about 5 to 500 microns. 1
Each measurement is completed in about 4 to 8 minutes.

Next, when measuring nitrite nitrogen, a predetermined amount of sample water is injected from the sample inlet 18 of the distillation section A2. Nitrite nitrogen in the injected sample water becomes nitrogen monoxide or nitrogen dioxide, and is entrained in the carrier gas introduced from the carrier gas introduction pipe 17, and after most of the entrained water is removed in the reflux condenser 7, it is passed through the conduit 6. The ammonia is then introduced into the reaction section 33, where it is reduced to ammonia and subjected to coulometric titration in the same manner as described above. In this case, nitrate nitrogen remains in the liquid in the distillation tank 19. The amount of sample water to be injected varies depending on the amount of nitrite nitrogen compound contained, but is usually about 5 μ to 5 ml. One measurement is completed in about 6 to 8 minutes.

When measuring nitrate nitrogen, the sample water is previously subjected to a reduction treatment to reduce nitrate nitrogen to nitrite ions, and then measured according to the method for measuring nitrite nitrogen described above. One measurement takes about 10 to 15 minutes.
The reduction treatment of the sample water may be performed, for example, according to the method of JIS-K0104. For example, 80ml of sample water becomes 100ml.
After adding 15 ml of neutral buffer solution and mixing, add 0.5 g of zinc powder and immediately add water up to the marked line. After shaking for 1 minute, remove unreacted zinc powder with paper and use the liquid as a sample.

To measure ammonia nitrogen, a predetermined amount of sample water is injected from the sample inlet 11 of the distillation section B4. The ammonia nitrogen in the injected sample water becomes ammonia gas, which is entrained in the carrier gas introduced from the carrier gas introduction pipe 10, and after most of the entrained water is removed in the reflux condenser 9, it passes through the conduits 8 and 22 and becomes a coulometric gas. Electrolytic cell 2 of titration section 23
7 and titrated coulometrically according to the method described above. The amount of sample water to be injected varies depending on the amount of nitrogen compounds contained, but is usually about 5 μ to 5 ml. One measurement is completed in about 6 to 8 minutes.

The content of organic nitrogen can be obtained by calculating the measured values of nitrite nitrogen, nitrate nitrogen, and ammonia nitrogen from the measured value of total nitrogen measured by the method described above.

As detailed above, the device of the present invention is configured by combining the distillation section A2 and the distillation section B4, which are not affected by water, with the measurement section 1, so that various forms of nitrogen can be obtained by changing the amount of sample collected. Compounds can be measured in each form down to ultra-trace amounts of around 0.002 ppm with high precision and in a short time, so it is suitable for total nitrogen analysis and analysis of nitrogen by form in environmental water, wastewater, agriculture, food, and pharmaceuticals. Extremely useful.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of a device according to the present invention. 1: Measuring section, 2: Distillation section A, 3: Control section, 4:
Distillation section B, 12, 19: distillation tank, 23: coulometric titration section, 29, 32: heating section, 30: acidic gas removal section, 33: reaction section.

Claims (1)

[Scope of Claims] 1. An apparatus for measuring ultratrace amounts of nitrogen by form, characterized by having the following measurement section, distillation section A, and distillation section B. (a) Measuring section A reaction section consisting of a cylindrical reaction tube filled with a reduction catalyst, which has a sample inlet and a hydrogen gas inlet at one end and a gas outlet at the other end.It has a gas inlet and a gas outlet. An acidic gas removal section filled with a solid alkaline substance inside the container; A heating section for heating the reaction section and the acidic gas removal section; A coulometric titration section having a gas inlet pipe, a gas outlet, an electrolytic electrode, an end point detection electrode, and an electrolytic tank. The reaction section and the acidic gas removal section are each housed in the heating section, the gas outlet of the reaction section is connected to the gas inlet of the acidic gas removal section, and the gas outlet of the acidic gas removal section is connected to the coulometric titration section. It is connected to a gas introduction pipe, and the gas introduction pipe is opened near the bottom of the electrolytic cell. (b) Distillation section A A distillation tank made of acid-resistant material and having a sample inlet, a carrier gas inlet pipe, and a generated gas outlet. It consists of a reflux condenser, and the carrier gas inlet pipe opens near the bottom of the distillation tank. The lower end of the reflux condenser is connected to the generated gas outlet of the distillation tank, and the upper end is connected near the sample inlet of the reaction section. (c) Distillation section B A distillation tank made of alkali-resistant material and having a sample inlet, a carrier gas inlet pipe, and a generated gas outlet. It consists of a reflux condenser, and the carrier gas inlet pipe opens near the bottom of the distillation tank. The lower end of the reflux condenser is connected to the generated gas outlet of the distillation tank, and the upper end is connected to the gas inlet pipe of the coulometric titration section.