JP2005164289A - Method of measuring nitrite ion and nitrate ion, and its instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of measuring a nitrite ion and an nitrate ion capable of shortening a measuring time and capable of simplifying constitution, because the nitrite ion and the nitrate ion are measured concurrently by the same measuring instrument, and provide its instrument. <P>SOLUTION: Sample water is measured automatically by simple constitution via two six-way valves 2, 3. When measuring nitrate ion concentration, the sample water is passed through a cadmium-copper column 4, and the nitrate ion is reduced to the nitrite ion to be measured. When measuring only the nitrite, the measurement therefor is carried out by the same instrument without passing the cadmium-copper column 4, and a nitrate ion concentration is found on the basis of a difference between the both. A mixture solution 9 mixed with a coloring reaction solution in the sample water is measured by a detector of a light emitting diode 10a and a photodiode 10b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a measurement method and apparatus for measuring concentrations of nitrite ions and nitrate ions contained in sample water. More specifically, the present invention relates to a method and an apparatus for measuring the concentration of nitrite ions and nitrate ions, in which sample water is supplied by switching valves and the absorbance is automatically measured and quantified.

  Industrial water, domestic wastewater, environmental water, seawater, and the like contain nitrous acid and nitric acid, causing various environmental pollution. Nitric acid in water is called the final decomposition product of animal organic matter produced by decomposition by bacteria through ammonia and nitrous acid. The amount of nitric acid is a barometer indicating past contamination with organic substances, and is a source of water contamination due to residues such as domestic wastewater. Nitrous acid is a harmful substance formed by oxidation of ammonia.

  In order to prevent the water from becoming dirty in this way, environmental standards and the like are established, and drainage regulations and the like are performed. A method for measuring the concentration of nitrous acid and nitric acid in water is defined in this standard, that is, JIS, and generally, the quality of water is determined based on this standard. This JIS standard uses a color reaction between a measurement substance and a color reagent, and various absorptiometric methods are known. For example, the measurement of nitric acid and nitrite ions in water is defined as follows.

  For nitrite ions, sulfanilamide (4-aminobenzenesulfonamide) was added to the sample by naphthylethylenediamine absorption photometry, and this was diazotized with nitrite ions to give N-1-naphthylethyleneamine (N-1 dichloride). -Measure the absorbance of the red colored azo compound produced by adding (naphthylethylenediammonium) to quantify nitrite ions.

  As for nitrate ions, there are reductive distillation-indophenol blue absorptiometry, reductive distillation-neutralization titration, copper / cadmium column reduction-naphthylethylenediamine absorptiometry, ion chromatography and the like. Of these, the copper-cadmium column reduction-naphthylethylenediamine absorption photometric method is used to reduce nitrate ions in a sample to nitrite ions by reducing them with a copper-cadmium column packed with cadmium particles with copper deposited on the surface. The total amount of nitrite ions present in the sample is quantified by the photometric method, and the concentration of nitrate ions is determined by the difference from the amount of nitrite ions in the same sample obtained separately.

This JIS regulation is performed manually using a graduated cylinder or the like. A method of automating and measuring this is also disclosed (see Patent Documents 2 to 4). For example, a movable column for sample suction and discharge that can be moved to an arbitrary position and a reduction column filled with a nitrate ion reduction catalyst are provided, A method is known in which a pump capable of sucking and discharging a certain amount of sample solution or reaction solution is provided, and the absorbance of the reaction product is measured by controlling an operating body such as a needle (see Patent Document 1).
JP-A-8-122258 JP 2002-228629 A JP 2003-207447 A JP 2001-194357 A

  In measuring nitrous acid and nitrate ions in water, the conventional manual measurement technique centered on JIS requires measurement time and may cause measurement errors, which is not efficient. In addition, the above-described automated disclosed technique is complicated and not portable, and measurement is not always efficient.

  Ideally, such environmental conservation measurements should be performed immediately on site and the results displayed. The present invention solves the conventional problems as a result of intensive studies based on the background of such conventional technology. An object of the present invention is to provide a measurement technology and apparatus for nitrous acid and nitric acid that can be carried and automatically measured in the field with a simple configuration using a valve for the concentration of both nitrite ions and nitrate ions in a sample water. It is in.

In order to achieve the above object, the present invention is achieved by the following means. That is,
The method for measuring nitrite ions and nitrate ions according to the first aspect of the present invention includes an injection step of injecting a predetermined amount of sample water into a predetermined container, and adding and mixing a reaction solution for color reaction of the sample water to obtain a mixed solution. A first step of measuring the concentration of nitrite ions, a step of developing a color reaction of the mixed solution, a step of developing a color reaction of the mixed solution, and a step of measuring a light transmittance of the mixed solution; A reduction process in which sample water is passed through a cadmium-copper reduction column by a carrier to reduce nitrate ions in the sample water to nitrite ions, and a mixing process in which a reaction solution is added to the reduced sample water and mixed to form a mixed solution A color development reaction step of causing the mixed solution to develop a color reaction, a second measurement step of nitrite ion concentration comprising a measurement step of measuring the light transmittance of the mixed solution, and the first measurement step. Comparing processing the measurement results of the serial second measuring step comprising a comparison processing step of calculating a nitrate ion concentration.

The method for measuring nitrite ions and nitrate ions according to the second aspect of the present invention is as follows.
The reaction solution in the mixing step is an acid solution in which sulfanilamide and N-1-naphthylethylenediamine are dissolved. The acid solution is a reagent solution obtained by dissolving sulfanilamide and N-1-naphthylethylenediamine dihydrochloride with an acid such as concentrated hydrochloric acid and diluting with distilled water.

The method for measuring nitrite ions and nitrate ions according to the third aspect of the present invention is as follows.
The carrier in the reduction step is an ammonium chloride solution containing ethylenediaminetetraacetate. The ethylenediaminetetraacetate is preferably disodium ethylenediaminetetraacetate or tetrasodium ethylenediaminetetraacetate.

The method for measuring nitrite ions and nitrate ions according to the present invention 4 is as follows.
The measuring step is characterized in that the measurement is performed by a measuring device in which the light source is a light emitting diode and the light receiver is a photodiode.

The method for measuring nitrite ions and nitrate ions according to the fifth aspect of the present invention is as follows.
The comparison processing step is characterized in that the nitrate ion concentration is quantified by subtracting and processing two nitrous acid measurement results from the measurement result by a computer.

The method for measuring nitrite ions and nitrate ions according to the sixth aspect of the present invention is as follows.
The peak wavelength of the light emitting diode in the measuring step is 500 nm to 600 nm.

The measuring device for nitrite ions and nitrate ions of the present invention 7
Sample water containing nitrite ions and nitrate ions, a valve that takes in the sample water, weighs the sample water, holds and feeds it in stages, a cadmium-copper reduction column that reduces nitrate ions in the sample water to nitrite ions, Ammonium chloride solution containing ethylenediaminetetraacetate added as a carrier to wash away the sample water, sulfanilamide and N-1-naphthylethylenediamine solution added as a coloring reaction solution to the sample water, and the N-1 in the sample water A fluorine-based tube for holding a mixed solution mixed with a naphthylethylenediamine solution to cause a color reaction, a measuring device for measuring the transmittance of the mixed solution to quantify the nitrite ion concentration, and the cadmium-copper reducing column The measurement result of the sample water passed through and the test not to pass through the cadmium-copper reduction column. It consists of a comparison processing device that quantifies the nitrate ion concentration by comparing the measurement results of the feed water.

The measurement apparatus for nitrite ions and nitrate ions of the present invention 8 is the present invention 7,
The valve is a 6-port switching valve, and is characterized in that the injected sample water is distributed in stages as a constant amount of sample water.

The nitrite ion and nitrate ion measuring apparatus according to the ninth aspect of the present invention is the invention 7,
The comparison processing device is a computer.

The measurement apparatus for nitrite ions and nitrate ions of the present invention 10 in the present invention 7,
The measuring apparatus is characterized in that the light source is a light emitting diode and the light receiving portion is a photodiode.

  The present invention has a simple configuration in which sample water can be supplied and measured through a valve, and the reaction solution is a solution dissolved in an acid solution, and the measurement result can be obtained in a short time. In addition, the nitrite ion and nitrate ion can be automatically measured alternately with the same sample water and quantified, thereby simplifying the configuration. As a result, it was possible to measure with high sensitivity and high accuracy in a short time, and there was no individual difference in the measurement result, and a stable measurement result was obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a measurement system 1 for measuring the concentrations of nitrite ions and nitrate ions. This measurement system 1 shows a case where a 6-way valve is applied. The basic measurement configuration of the present invention is constituted by two 6-way valves as shown in FIG. The first six-way valve 2 is provided with six ports a, b, c, d, e, and f, and can be indexed and changed in position by rotation.

  This rotation may be manual if it has a simple structure, but it is preferable that the rotation is automatic when the measurement is continuously repeated. Similarly, the second six-way valve 3 is also provided with six ports g, h, i, j, k, l, and can be indexed and changed in position by rotation. Between the two six-way valves, a circuit 5 through which the sample water passes the cadmium-copper column 4 and a circuit 6 through which the sample water passes directly are connected.

  In the first six-way valve 2, the sample water is supplied to the port a, flows to the port b, and is supplied to the second six-way valve 3 through the ports e and f. Next, when the first six-way valve 2 is switched, the sample water between the ports a and b is repositioned between the ports c and d. The c port is connected to the carrier container 7, and the sample water between the ports c and d is pushed to the cadmium column-copper 4 side by the carrier 7 a supplied from the carrier container 7. The carrier 7a is an ammonium chloride solution containing ethylenediaminetetraacetate.

  Next, when the first six-way valve 2 is switched, the position between the ports c and d changes between the ports e and f. At this time, the carrier remains between the ports c and d, and there is no sample water. By switching the ports to e and f, the circuit connection is made so that new sample water is supplied to the port a which is the sample water supply port. As a result, the carrier between the ports e and f is pushed into the second 6-way valve 3 together with the sample water, and this circuit is filled with the sample water.

  The first 6-way valve 2 has such a configuration, and when measuring nitric acid, the sample water is positioned at the ports c and d and is pushed to the cadmium-copper column 4 side by the carrier 7a, and the nitric acid is sublimated. It is nitrated and fed to the second 6-way valve 3. Nitric acid is quantitatively reduced to nitrous acid as it passes through the cadmium-copper column 4. The sample water passing through the cadmium-copper column 4 is a total of nitrous acid reduced from nitric acid and nitrous acid originally contained.

  Next, the second six-way valve 3 will be described. The second six-way valve 3 also has six ports g, h, i, j, k, and l like the first six-way valve 2. The sample water is supplied to the port g through the port f of the first six-way valve 2. The supplied sample water is discharged through the ports g, h, k, and l when not measured.

  On the other hand, the sample water from the cadmium-copper column 4 passes through the ports i and j as ion water of nitrous acid and is brought to the T position. After the sample water passes, only the carrier 7a remains in the cadmium-copper column 4. At this T position, sulfanilamide and N-1-naphthylethylenediamine solution, which are color reaction solutions 8a, are supplied from the color reaction solution container 8 and mixed with sample water. In this mixing process, the carrier 7a only pushes the sample water and does not affect the measurement result.

  On the other hand, when measuring only nitrite ions, after measuring the nitrate ions, the second six-way valve 3 is switched, and the sample water between the ports g and h is positioned at the ports i and j. The sample water between the ports i and j is the same as that at the time of nitrate ion measurement, and is brought to the T position by the carrier 7 a supplied through the cadmium-copper column 4. After the measurement of only the nitrite ion is completed, the nitrate ion is measured again. Thus, the sample water for measuring nitrate ions and nitrite ions at the time of measurement always remains in the first 6-way valve 2 and the second 6-way valve 3 in a continuous flow, and is homogeneous. belongs to.

  In this way, measurement of nitrate ions and nitrite ions of homogeneous sample water can be alternately and repeatedly performed using the same apparatus. Since the sample water can be flown continuously, the previous sample water is flowed by switching the valve port, so the previous sample water does not remain in this circuit, and fresh sample water is always measured. it can. At the position T, the sample water is mixed with the coloring reaction solution 8a to become a mixed solution 9. The sample water is diazotized and becomes the reddish purple of the azo dye.

  This mixed solution 9 passes through the reaction coil RC and is brought to the detection device 10 at room temperature. The mixed solution 9 is subjected to a color reaction with the detection device 10 and measured. In this measurement, the transmittance of the mixed solution 9 is measured to determine the degree of nitrite ion content. Although details are not shown, the sample water, the carrier 7a, and the coloring reaction solution 8a are supplied by an actuator 12 such as a pump or a cylinder.

  As shown in FIG. 2, the detection device 10 has a light emitting part as a light emitting diode 10a and a light receiving part as a photodiode 10b. The light emitting diode 10a has a wavelength of 500 to 600 nm, and the optical path length is in the range of 10 to 50 mm. As shown in the figure, the mixed solution 9 flows from the light emitting diode 10a side to the photodiode 10b side. The concentration of nitrite ions is measured in the optical path C along the way. Light enters during this flow process.

  This concentration measurement is to measure the transmittance of the mixed solution 9 as described above. The mixed solution 9 that has passed through the measurement device 10 is drained outside the detection device 10. Although the mixed solution 9 is drained, the measurement result is sent as data to the computer 11 via a signal amplifier and subjected to a comparison calculation process. FIG. 3 shows an output example of known nitrite ion and nitrate ion concentration data. In this comparison calculation, a total amount of nitrate ion concentration and nitrite ion concentration is obtained from a calibration curve of absorbance obtained by measuring a large amount of sample water stepwise through a cadmium-copper column, and similarly, cadmium-copper Processing is based on determining the concentration of nitrate ions by subtracting the concentration of nitrite ions measured without passing through the column.

  The quantitative value of nitrite ions measured through the cadmium-copper column 4 is the total amount of the concentration of nitrite ions originally present and the concentration of nitrite ions reduced from nitrate ions. . By subtracting the measured value of the nitrite ion concentration measured without passing through the cadmium-copper column 4 in this comparative calculation process, the amount of nitrate ion can be calculated and quantified. That is, the following relational expression is obtained. First measured value = nitrite ion concentration, later measured value = nitrite ion concentration + nitrate ion concentration, nitrate ion concentration = later measured value-first measured value.

  As described above, the measurement system 1 has a function capable of separately quantifying the nitrate ion concentration separately from the nitrite ion. Since the computer 11 can be configured to be relatively small, it can be a compact system device that can be used by being attached to the above-described device and being taken to an outdoor site. Although the embodiment of the present invention has been described above, it goes without saying that the specific configuration of the present invention is not limited to this embodiment. For example, although the valve has been described as a six-way valve, other valves may be used.

Examples of the present invention are shown below.
Analysis box: W400mm × D300mm × H370mm
Analysis box weight: approx. 10kg
Carrier: Ammonium chloride solution containing ethylenediaminetetraacetic acid disodium or ethylenediaminetetraacetic acid tetrasodium Coloring reaction solution: 1.0 g of sulfanilamide and 0.06 g of N-1-naphthylethylenediamine dihydrochloride in 2 mL of concentrated hydrochloric acid Reagent solution cadmium-copper column dissolved and diluted to 200 mL with distilled water: 25 × 2 ml. d
Flow rate: 0.3 ml / min
Sample loop: 250 μl
Reaction coil length: 60cm
Optical path length: 1-5cm
Wavelength of detection device: 540 nm
Detector: Light-emitting diode (LED), photodiode (PD)

FIG. 1 is a configuration diagram of a measurement system of a measurement apparatus for nitric acid and nitrous acid according to the present invention. FIG. 2 is a configuration diagram of the detection apparatus. FIG. 3 is an example of data output when measuring known nitric acid and nitrous acid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measuring system 2 ... 1st 6 way valve 3 ... 2nd 6 way valve 4 ... Cadmium-copper column 5, 6 ... Circuit 7a ... Carrier 8a ... Coloring reaction solution 9 ... Mixed solution 10 ... Detection apparatus 11 ... Computer 12 ... Actuator

Claims (10)

An injection step of injecting a predetermined amount of sample water into a predetermined container;
A mixing step in which a reaction solution is added and mixed to cause a color reaction of the sample water;
A first measuring step of nitrite ion concentration comprising a coloring reaction step of causing the mixed solution to develop a coloring reaction, and a measuring step of measuring the light transmittance of the mixed solution;
A reduction step in which the sample water injected in the injection step is passed through a cadmium-copper reduction column by a carrier and nitrate ions in the sample water are reduced to nitrite ions;
A mixing step of adding a reaction solution to the reduced sample water and mixing to obtain a mixed solution;
A color development reaction step for causing a color reaction of the mixed solution, a second measurement step of nitrite ion concentration comprising a measurement step for measuring the light transmittance of the mixed solution,
A method for measuring a nitrite ion concentration and a nitrate ion concentration, comprising: a comparison processing step of calculating a nitrate ion concentration by performing a comparative calculation process on the measurement results of the first measurement step and the second measurement step. In the measuring method of nitrite ion and nitrate ion according to claim 1,
The method for measuring nitrite ions and nitrate ions, wherein the reaction solution in the mixing step is an acid solution in which sulfanilamide and N-1-naphthylethylenediamine are dissolved. In the measuring method of nitrite ion and nitrate ion according to claim 1,
The method for measuring nitrite ions and nitrate ions, wherein the carrier in the reduction step is an ammonium chloride solution containing ethylenediaminetetraacetate. In the measuring method of nitrite ion and nitrate ion according to claim 1,
The method for measuring nitrite ions and nitrate ions is characterized in that the measurement step is measurement by a measurement device in which the light source is a light emitting diode and the light receiver is a photodiode. In the measuring method of nitrite ion and nitrate ion according to claim 1,
The method for measuring nitrite ions and nitrate ions is characterized in that the comparison processing step is a step of subtracting two nitrite measurement results from a measurement result by a computer and quantifying the nitrate ion concentration. The method for measuring and measuring nitrite ions and nitrate ions according to claim 4,
The method for measuring nitrite ions and nitrate ions, wherein the peak wavelength of the light emitting diode in the measuring step is 500 nm to 600 nm. Sample water containing nitrite ions and nitrate ions;
A valve that takes in the sample water, is calibrated to a predetermined amount, held and supplied in stages;
A cadmium-copper reduction column for reducing nitrate ions in the sample water to nitrite ions;
An ammonium chloride solution containing ethylenediaminetetraacetate added as a carrier to flush the sample water;
Sulfanilamide and N-1-naphthylethylenediamine solution added as a coloring reaction solution to the sample water,
Holding a mixed solution obtained by mixing the sample water with the N-1-naphthylethylenediamine solution;
A measuring device for measuring the transmittance of the mixed solution to quantify the nitrite ion concentration;
A sub-process comprising: a comparison processing device for comparing and calculating a measurement result of sample water that has passed through the cadmium-copper reduction column and a measurement result of sample water that does not pass through the cadmium-copper reduction column to quantify nitrate ion concentration. Nitrate ion and nitrate ion measuring device. In the measuring device of nitrite ion and nitrate ion according to claim 7,
The valve is a 6-port switching valve, and is configured to distribute and supply the injected sample water in a stepwise manner as a constant amount of sample water. In the measuring device of nitrite ion and nitrate ion according to claim 7,
The apparatus for measuring nitrite ions and nitrate ions is characterized in that the comparison processing device is a computer. In the measuring device of nitrite ion and nitrate ion according to claim 7,
The measuring apparatus is a measuring apparatus in which a light source is a light emitting diode and a light receiving portion is a photodiode, and the measuring apparatus for nitrite ions and nitrate ions is characterized in that:

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