JP2764986B2 - Nitrite determination device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for determining nitrite in a sample. The apparatus for determining nitrous acid can be widely used as a monitor for the treatment process of water supply and sewage treatment, or as an analyzer for nitrite in food and biological samples.

(Prior Art) As an apparatus for quantifying nitrous acid, an apparatus that generates an azo dye using a diazotization reaction and measures the absorbance of the dye is generally used.

(Problems to be Solved by the Invention) Since the light absorption device is interfered with by suspended or colored substances in the sample, the quantitative value of nitrite in complex samples such as sewage, food, biological samples, etc. is not very accurate. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a quantitative device capable of selectively and continuously accurately measuring nitrous acid in a sample without interference of a suspension or coloring matter in the sample.

(Means for Solving the Problems) In the present invention, a microporous organic that does not react with nitric oxide,
Alternatively, a sample solution comprising a mixture of a sample containing nitrous acid and a reducing agent that reduces nitrous acid to nitric oxide at one of the inlet sides of the membrane separator where the two flow paths contact each other via an inorganic polymer membrane. A sample inflow pipe for flowing a solution into which a gas that does not react with nitrous acid and nitric oxide is blown is connected to a gas inlet pipe for flowing a carrier gas to the other of the inlet side, and an outlet side of the membrane separator is connected to the other side of the inlet side. A gas outlet pipe for sending a carrier gas containing nitric oxide, which is a reaction product separated by the membrane separator, to a nitric oxide detector is connected to the carrier side,
A sample outlet pipe for discharging the sample solution is connected to the sample side on the outlet side, and the amount of nitrous acid in the sample is determined.

In the present invention, a carrier gas dehydrator is further inserted between the gas outlet pipe and the nitric oxide detector.

As the organic polymer film, Teflon (trade name of DuPont of polytetrafluoroethylene), vinyl acetate, vinyl chloride, viton, polystyrene, polyester, nylon, or the like can be used. Further, molten glass, microporous glass, ceramic, or the like can be used as the inorganic polymer film.

(Action) Nitric acid in the sample is changed into gaseous nitric oxide by a reducing agent such as iodide, and the nitric oxide permeates through the microporous polymer membrane in the membrane separator as gas. The permeated nitric oxide is diffused into a carrier gas and detected by a nitric oxide detector such as a chemiluminescence detector to measure nitrous acid in the sample.

When a gas that does not react with nitrous acid and nitric oxide is blown into the sample solution, the detection sensitivity is improved.

The reason is that the nitrogen monoxide dissolved in the sample solution reduced by the reducing agent such as potassium iodide transfers to the injected gas to permeate the membrane separator more efficiently.

Further, by blowing the gas, the flow of the sample solution in the tube changes from laminar flow to turbulent flow. When the flow of the sample solution in the tube becomes turbulent, the dust and the precipitates generated by the chemical reaction contained in the sample solution adhere to the polymer membrane surface in the membrane separator and cause clogging. To prevent.

And so on.

The reason why the carrier gas is passed through the dehydrator is to remove moisture, which has an adverse effect on a chemiluminescence detector or the like.

(Embodiment) FIG. 1 shows an embodiment of the present invention.

Reference numeral 1 denotes a membrane separator, which comprises a double tube of an outer Teflon tube 2 and an inner microporous Teflon tube 3. As the inner microporous Teflon tube 3, for example, Japan Gore-Tex Corporation TB series (porosity 70%, maximum pore diameter 3.5 μm) or the like can be used. For example, TB002 has an inner diameter of 2 mm and an outer diameter of 2.8 mm. Since the length of the microporous Teflon tube 3 affects the sensitivity, it is used with an appropriate length. For example, its length is 50 cm.

The sample is sucked by the pump 4 and sent to the Teflon tube 2 outside the membrane separator 1 via the sample inflow tube 20. The sample inflow pipe 20 is blown with a potassium iodide solution as a reducing agent from the pump 5, dilute sulfuric acid from the pump 6 and air from the pump 7. Another reducing agent such as potassium halide may be used instead of potassium iodide, and another acid such as phosphoric acid may be used instead of dilute sulfuric acid. Instead of air, a gas such as nitrogen, helium, or argon that does not react with nitric oxide may be used.

The inside of the microporous Teflon tube 3 is supplied with air as a carrier gas by the pump 8 through the gas inflow tube 22.
The inner microporous teblon tube 3 is connected to a gas outlet tube 24,
After the gas outlet pipe 24, the light emitted from the chemiluminescence detector 13 passes through the dehydrator 9.
Is connected. The sample outlet pipe 11 is connected to the outlet side outside the microporous Teflon pipe 3.

The dehydrator 9 has an outer Teflon tube 2a and an inner Nafyon tube
It is composed of ten double tubes, and air as a carrier gas is sucked between the two tubes 2a and 10 by the pump 12.

The chemiluminescence detector 13 measures the chemiluminescence of ozone and nitric oxide by flowing ozone. Chemiluminescence detector
The signal from 13 is output to the recorder.

The air from the pump 7 need not be sent. In this case, the sensitivity is about one-third compared to the case where air is sent.
To decline.

It is considered that this is because the permeation efficiency of the microporous Teflon tube 3 inside the membrane separator 1 decreases.

Alternatively, the carrier gas may flow outside the microporous Teflon tube 3, while the sample solution may flow inside the microporous Teflon tube 3. In this case, the dehydrator 9 needs to be connected to the pipe 11.

FIG. 2 shows a membrane separator 14 in still another embodiment. A plurality of hollow fibers 15 are bundled, a sample solution flows inside the hollow fibers 15, and a carrier gas flows outside the hollow fibers. As a material of the microporous hollow fiber 15, Teflon or cellulose acetate is preferable. In this case, the carrier gas may flow inside the hollow fiber 15 and the sample solution may flow outside.

FIG. 3 shows a membrane separator 16 in still another embodiment. The microporous polymer film 17 is sandwiched between the upper chamber and the lower chamber in a plate shape. The sample solution is guided to the upper chamber, and the carrier gas flows to the lower chamber. In this case, the upper and lower chambers may be reversed.

(Effect of the Invention) In the present invention, nitrite in a sample could be continuously and selectively quantified.

FIG. 4 shows the calibration relationship between the logarithmic value of the nitrite concentration in the sample and the signal from the chemiluminescence detector. Nitrite concentration 5ppb
As described above, a good linear relationship with the signal was recognized.

Assuming that the lower limit of quantification is S / N = 3 based on FIG. 4, the lower limit of quantification of nitrite ions in the solution of the quantification apparatus of the present invention is 0.
4ppb.

Table 1 shows the interference of various chemical species in the solution with the device and the spectrophotometry. Species that interfered with the spectrophotometry did not interfere with this device.

By blowing a gas that does not react with nitrous acid and nitric oxide into the sample solution, the detection sensitivity of the nitric oxide detector was improved about three times.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing one embodiment of the present invention, FIG. 2 is a schematic sectional view showing a membrane separator in another embodiment, and FIG. 3 is still another embodiment. FIG. 4 is a schematic perspective view showing the membrane separator in FIG. 1,14,16 …… membrane separator, 3,15 …… microporous Teflon tube, 17 …… microporous Teflon membrane, 10 …… Nafyon tube, 4,5,6,7,8,12 …… Pump 13 Chemiluminescence detector 11 Sample outflow tube 20 Sample inflow tube 22 Gas inflow tube 24 Gas outflow tube

Claims (3)

(57) [Claims] 1. A sample containing nitrite at one of the inlet sides of a membrane separator in which two flow paths contact each other via a microporous organic or inorganic polymer membrane that does not react with nitric oxide. To a sample solution consisting of a mixed solution with a reducing agent that reduces nitrogen to nitric oxide. Connect the incoming gas inlet pipe,
A gas outlet pipe for sending a carrier gas containing nitric oxide, which is a reaction product separated by the membrane separator, to a nitric oxide detector is connected to the carrier side on the outlet side of the membrane separator, and the sample side on the outlet side is connected. A device for determining nitrous acid in a sample, which is connected to a sample outlet pipe for discharging a sample solution. 2. The apparatus for quantifying nitrous acid in a solution according to claim 1, wherein a carrier gas dehydrator is inserted between the gas outlet pipe and the nitric oxide detector. 3. The apparatus for quantifying nitrous acid in a solution according to claim 1, wherein a chemiluminescence detector is used as the nitric oxide detector.