JPS6345062B2 - - 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 total nitrogen, nitrite nitrogen, and nitrate 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 hydrogen eutrophication, 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, a device for measuring ultra-trace amounts of nitrite nitrogen and nitrate nitrogen by form uses helium as a carrier gas, and reduces nitrite nitrogen in sample water with an amidosulfonic acid reaction solution to nitrogen gas in a reaction tube.
An apparatus has been proposed in which the entrained water is completely removed and then quantified by gas chromatography, and the nitrate nitrogen is reduced to nitrite ions with zinc powder and then measured by the method described above. However, with this device, dissolved nitrogen gas in the reaction solution and sample water must be completely removed, and entrained water must be completely removed even after reduction to nitrogen gas, so pretreatment operations are required. This method has the drawbacks of being time consuming and complicated to operate.

The present invention provides an apparatus for measuring ultratrace amounts of nitrogen by form, which does not have such drawbacks, and the gist thereof is (1) an apparatus for measuring ultratrace amounts of nitrogen according to its form, which is characterized by having the following measuring section and distillation section: Separate measuring device.

(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 fixed 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 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. The carrier gas inlet pipe opens near the bottom of the distillation tank, and the reflux The lower end of the 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.

exists in

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 measuring section, 2 is a distillation section, 3 is a control section, 12 is a distillation tank, 17 is a coulometric titration section, 21 and 24 are heating sections, 2
2 is an acidic gas removal section, and 25 is a reaction section.

The measurement unit 1 includes a reaction unit 25 for reducing nitrogen compounds in a sample and converting them into ammonia, an acid gas removal unit 22 for removing acid gas from the converted gas, and a coulometric unit for quantifying ammonia. It is composed of a titration section 17.

The reaction section 25 has a cylindrical reaction tube having a sample inlet 4 and a hydrogen gas inlet tube 26 at one end and a gas outlet at the other end. It is filled with a metal catalyst made by coating the surface of inert particles such as alumina with these metals. 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 section 25 is housed in a heating section 24 such as an electric furnace having a built-in heating wire, and is maintained at a high temperature of about 300 to 600°C.

The acid gas removal section 22 is for removing acid 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 and potassium carbonate with asbestos.
The acid gas removal section 22 is housed in the heating section 21 similar to the heating section 24, and is maintained at a temperature of about room temperature to 300°C.

The coulometric titration unit 17 is for quantifying ammonia in the gas discharged from the acidic gas removal unit, and includes an electrolytic tank 19 with a sliding lid, an electrolytic electrode 15 installed in the tank, a detection electrode 16, and a gas inlet. It is composed of a pipe 18 and a gas outlet pipe 14. Each electrode 15, 16 and gas introduction pipe 18 are installed at a position where the lower end is submerged in the electrolyte.

The distillation section 2 is for expelling nitrite nitrogen in the sample as nitrogen monoxide or nitrogen dioxide gas, and includes a distillation tank 12 having a sample inlet 11, a hydrogen gas inlet pipe 10, and a generated gas outlet; It is composed of a reflux condenser 6 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 30 to 80 wt%, preferably 30 to 50 wt% of a non-volatile strong acid such as sulfuric acid or phosphoric acid.
Since the aqueous solution is put therein, it is preferable to use an acid-resistant material such as glass, ceramic, stainless steel, etc.

It is preferable that the reflux condenser 6 has an obstacle in the gas flow path to avoid volatilization of the mist.
Normally, a corrugated pipe is used, but if it is a straight pipe, it may be used with a filler.

The lower end opening of the reflux condenser 6 is connected to the generated gas outlet of the distillation tank 12, and the upper end opening is connected to the vicinity of the sample inlet 4 of the reaction section 25 through the conduit 5. The distillation tank 12 is heated by a heater 13 to 70°C to the boiling temperature of the liquid, preferably 80 to 90°C.

The control unit 3 usually includes a coulometric titration control device 7, a temperature control device 8, and a gas flow rate control device 9. In the coulometric titration control device 7, the detection electrode 1
The electric signal corresponding to the hydrogen ion concentration obtained from step 6 is amplified, converted into a current output proportional to the deviation from the end point PH value, and an electrolytic current is supplied to the electrolytic electrode 15. On the other hand, if necessary, this electrolytic current is calculated as a current by subtracting the Planck current, converted into analytical value units, and after performing correction calculations such as a sampling amount coefficient to indicate the ratio to the collected sample, it is integrated and converted into an electrical quantity. Displayed as a direct reading of a fair analysis.

The temperature control device 8 is for adjusting the temperatures of the heating sections 21 and 24 and the heater 13 to a predetermined temperature.

The gas flow rate control device 9 is for adjusting the flow rates of hydrogen gas and carrier gas introduced from the hydrogen gas introduction pipe 10 and the carrier gas introduction pipe 26 to predetermined amounts. The flow rate of hydrogen gas is usually 200
~700ml/min, preferably 400-500ml/min. Further, hydrogen gas, nitrogen gas, argon gas, etc. are used as the carrier gas.

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 through the sample inlet 4 of the measuring section 1. The injected sample water is passed through the hydrogen gas introduction pipe 26.
The reaction part 25 is entrained by the hydrogen gas introduced from
All nitrogen compounds are reduced to ammonia.
The generated ammonia gas is sent to conduit 2 along with hydrogen gas.
3 into the acid gas removal section 22, where the coexisting acid gas is removed. Then conduits 20 and 18
The sample is then introduced into the electrolytic cell 19, 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 19, and coulometric titration is performed. The titration results are displayed on the coulometric titration control device 7. The amount of sample water injected varies depending on the amount of nitrogen compounds contained, but is usually about 5 to 500 microns.
One 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 11 of the distillation section 2. 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 10, and after most of the entrained water is removed in the reflux condenser 6, it is transferred to the conduit 5. The ammonia is then introduced into the reaction section 25, 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 12. 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.

That is, put 80 ml of sample water into a 100 ml volumetric flask, add 15 ml of neutral buffer solution and mix, then add 0.5 g of zinc powder and immediately add water up to the marked line. 1
After shaking for a minute, separate the unreacted zinc powder with paper and use the liquid as a sample.

As described in detail above, the device of the present invention is configured by combining the distillation section 2, which is not affected by water, with the measurement section 1, so that by measuring the total nitrogen amount and changing the amount of sample collected, it is possible to Since it is possible to measure nitrite nitrogen and nitrate nitrogen in ultra-trace amounts with high accuracy and in a short time, it can be used for total nitrogen analysis and nitrite nitrogen in environmental water, wastewater, agriculture, food, and pharmaceuticals. It is extremely useful for analyzing the forms of nitrate and nitrogen.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of a device according to the present invention. 1: Measuring section, 2: Distillation section, 3: Control section, 12:
Distillation tank, 17: coulometric titration section, 21, 24: heating section, 22: acidic gas removal section, 25: reaction section.

Claims (1)

[Scope of Claims] 1. An apparatus for measuring ultratrace amounts of nitrogen by form, characterized by having the following measuring section and distilling section. (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. A coulometric titration having 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 gas introduction pipe, a gas outlet, an electrolytic electrode, an end point detection electrode, and an electrolytic cell. 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. The gas inlet pipe is connected to the gas inlet pipe, and the gas inlet pipe is opened near the bottom of the electrolytic cell. (b) Distillation section A distillation tank made of acid-resistant material and equipped with 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 to allow reflux. The lower end of the 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.