JPS62449B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for correctly and automatically measuring inorganic nitrogen, more specifically, the total content of nitrate nitrogen and nitrite nitrogen (hereinafter referred to as the total amount) in water. be. [Prior art] Inorganic nitrogen exists in three states: ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen, and when these are mixed with wastewater and released, especially into inland seas and lakes, they can cause red tide in water bodies. becomes. Therefore, those involved are continuing to make efforts to prevent inorganic nitrogen-containing wastewater from being discharged, but efforts are also being made to establish a monitoring system for discharge, especially a method to automatically measure the content of inorganic nitrogen in water. ing. Among the three forms of inorganic nitrogen, the content of ammonia nitrogen can be measured with considerable accuracy using an ion-selective electrode, so automatic measurement is not an important issue at the moment.
Establishing a method to automatically measure the total amount of nitrate nitrogen and nitrite nitrogen is an important issue. However, although there are methods for measuring nitrogen alone, there is no effective method for measuring the total amount. For example, conventional methods for quantifying nitrate nitrogen in water include a method using a bolagraph by R.L. Young et al., a method using an ion-selective electrode by L.R. Matsukenzie et al., a method using an ion-selective electrode by S.・There is a fluorescence photometry method by K. Afghan et al., and methods for measuring the ultraviolet absorption of nitrate nitrogen include a method of measuring absorbance at 210 nm, a method of subtracting four times the absorbance at 275 nm from the absorbance at 210 nm, and a method of subtracting four times the absorbance at 275 nm from the absorbance at 220 nm. Method of subtracting 2.5 times the absorbance at 275 or 215nm, 220nm, 205nm, 210nm,
There are methods such as measuring the absorbance at 225 nm and 230 nm and calculating the nitrate nitrogen content after performing complicated calculations. Further, as a method for measuring only nitrite nitrogen, there is a method using a spectrophotometric method using a special organic reagent. However, neither method can measure the total amount of nitrate nitrogen and nitrite nitrogen. However, only British Patent No. 1309551 proposes a method for measuring the total amount of nitrogen oxides as well as organic carbon and suspended matter in water, but this method uses a device with a complicated special structure. Because it has to be done easily, nitrogen oxides cannot be measured everywhere using this method. Since both nitrate nitrogen and nitrite nitrogen are eutrophication sources that cause red tide, it is easy and accurate to calculate their total content without measuring their individual contents. If this method can be used in combination with the method for measuring ammonia nitrogen, it will be possible to measure inorganic nitrogen in water and strengthen the pollution monitoring system, which is extremely significant from an industrial or pollution prevention standpoint. In general, in spectrophotometric analysis, a number of specific wavelengths in the spectrum are selected, the absorbance at those wavelengths is measured, and the content of each of the several components contained in the sample is determined by calculation. Methods are known. The inventor's intention with this method is to accurately measure the total amount of two types of nitrogen compounds with different embodiments, and at the same time that the intended purpose is different from the conventional method, it is rather Considering the field of application of the present invention, the inventor's intention is reasonable. Therefore, the inventors of the present invention have conducted intensive studies on methods for measuring the total amount of nitrate nitrogen and nitrite nitrogen, and have found that the above content can be accurately measured by measuring the absorbance at a specific wavelength and performing calculations based on this. I have come to discover this fact. [Object of the Invention] Therefore, an object of the present invention is to establish a method for accurately measuring the total amount of nitrate nitrogen and nitrite nitrogen. [Structure of the Invention] That is, the method of measuring the total amount of nitrate nitrogen and nitrite nitrogen of the present invention is to measure the total amount of nitrate nitrogen and nitrite nitrogen using ultraviolet rays of two standard samples each containing the same amount of nitrate nitrogen and nitrite nitrogen. arbitrary wavelengths λ ₂ and _{λ 3 of} the absorption spectra S _{1 and S 2 ,}
The difference between the respective absorbances E ₂₁ and E ₂₂ of S ₂ (E ₂₁ −
E ₂₂ ) and the absorbance E _{2 and} E ₃ of the standard solution at wavelengths λ ₂ and λ ₃ such that the difference (E ₃₁ − E ₃₂ ) between E 31 and E ₃₂ are equal are measured. Similarly, the absorbance at the wavelengths λ ₂ and λ ₃ is
Measure E′ ₂ and E′ ₃ , and calculate the total amount of nitrate nitrogen and nitrite nitrogen in the sample to be measured from E ₂ −E ₃ and E′ ₂ −E′ ₃ based on the Lambard-Bell law. It is characterized by calculating. The method of the present invention will be specifically explained using figures. First, two standard samples of artificial seawater containing the same amount of nitrate nitrogen and nitrite nitrogen, for example, 1.0 ppm, were prepared, and artificial seawater containing no nitrogen was used as a control solution. Measure the absorbance of these ultraviolet rays to obtain a spectrum.
Then, a spectrum as shown in FIG. 1 is obtained. That is, curve A is the ultraviolet absorption spectrum of nitrate nitrogen S ₁
, curve B is the ultraviolet absorption spectrum S ₂ of nitrite nitrogen, and both spectra S ₁ and S ₂ are at the wavelength λ
₁ = 219 nm and exhibits absorbance E ₁ = 0.3. On the other hand, the two spectra S _{1 and} S ₂ also intersect at the wavelength λ ₄ which is larger than the wavelength λ 1, and in the spectra S ₁ and S ₂ between them, the wavelengths λ ₂ and λ ₃ are arbitrary, and Its wavelength λ ₂
The difference between the absorbances _{E 21 , E 22} and E ₃₁ , _{E 32} of spectra _{S 1} and S ₂ at
−E ₃₂ ) are equal to λ ₂ and λ ₃ . In the above 1.0ppm sample, λ ₂ = 223n
m, λ ₃ = 232 nm, E ₂₁ = 0.21, E ₂₂ = 0.07, E ₃₁
= 0.26, E ₃₂ = 0.12. In the present invention, next, the absorbances E ₂ and E ₃ of the sample whose nitrogen oxide content is to be measured are measured at the above λ ₂ and λ ₃ , and the difference in absorbance (E ₂ - E ₃ ) is calculated. Then, the total amount of nitrate nitrogen and nitrite nitrogen is determined using Lambard-Bell's law. In this way, the total amount of the above two nitrogen states in water can be immediately and accurately measured without determining the individual contents of nitrate nitrogen and nitrite nitrogen and adding them together. In other words, in the above λ ₂ and λ ₃ , the same absorbance difference (E ₂ - E ₃ ) will be given for both nitrate nitrogen and nitrite nitrogen if the content is the same, but if they are measured at different wavelengths, In this case, the measurement value will be inaccurate because the two nitrogen states will have different absorbances. [Effect of the invention] As described above, in the measurement method according to the present invention, λ ₂ , λ
₃ are the same for amphoteric nitrogen (E ₂ −
E ₃ ), a high accuracy of measurement is guaranteed. [Example] Next, the effects of the present invention will be shown with examples. Example 1 Total amount of nitrate nitrogen and nitrite nitrogen is 1.0 ppm
, and create artificial seawater with different proportions of each.
The absorbances E ₂ and E ₃ at wavelengths of 223 nm and 232 nm were measured, and the difference between them was calculated, and the results are shown in the curve of FIG. 2. This curve shows that the absorbance does not change even if the ratio of nitrate nitrogen to nitrite nitrogen changes, that is, the method of the present invention is accurate. In this example, when the accuracy of the measurement results was calculated, the minimum coefficient of variation was 4.2% and the maximum was 7.5%, indicating that the accuracy of the method of the present invention was high. In addition, we created artificial seawater in which the total amount of nitrate nitrogen and nitrite nitrogen was 2.0 ppm, and the proportions of each were different. As a result of similar measurements, the absorbance difference calculated from the measured absorbances E ₂ and E ₃ was (E ₂ −E ₃ ) was exactly twice that in the case of a total amount of 1.0 ppm. The accuracy calculated in the same way is a minimum of 2.1% for the coefficient of variation.
The maximum was 3.3%. Example 2 Mixing ratio of nitrate nitrogen and nitrite nitrogen is 1:1
, we created artificial seawater with various amounts of total nitrogen, that is, the total content of both nitrogen states, and found that λ ₂ = 223n
The absorbance E ₂ at m and the absorbance E 3 at λ ₃ =232 nm were measured, and the absorbance difference (E ₂ −E _{3 )} was calculated. The results are shown in Figure 3. As can be seen from this, as the total nitrogen content in artificial seawater increases, the absorbance difference (E ₂ − _{E 3} ) increases linearly. It can be seen that the total amount of can be determined. Example 3 Nitrate nitrogen 0.80ppm, nitrite nitrogen 0.20ppm
We coexisted various amounts of various organic and inorganic substances in artificial seawater with a total concentration of 1.00 ppm, and examined whether they interacted with each other. In this case, λ ₂ =
The absorbance E ₂ at 223 nm and the absorbance E ₃ at λ ₃ =232 nm were measured, and the absorbance difference (E′ ₂ −E′ ₃ ) was calculated. On the other hand, the absorbance difference (E ₂ − _{E 3} ) was determined in the same way for artificial seawater (standard sample) with the same nitrate and nitrite concentrations as above, which does not contain coexisting substances, and (E ₂ −
The total amount of nitrate nitrogen and nitrite nitrogen was calculated from E ₃ ) and (E′ ₂ −E′ ₃ ) according to Lambard-Bell's law, and the error was determined. The results are shown in Table 1.

[Table] As can be seen from Table 1, the value of E ₂ −E ₃ can be measured with a small error in the coexistence of relatively large amounts of organic and inorganic substances, and therefore The total amount of nitrogen can be determined correctly. Example 4 The total amount of nitrate nitrogen and nitrite nitrogen in the seawater in Kobe Port is expressed as the absorbance E ₂ and λ at λ ₂ = 223 nm.
It was determined by measuring the absorbance _E3 at ₃ =232 nm and calculating the absorbance difference ( _E2 - _E3 ). In that case, use two types of cells, 10.0 mm and 50.0 mm, and
Measurements were taken one time at a time. On the other hand, for the standard solution, the absorbance at the two wavelengths was similarly measured, the absorbance difference was calculated, and the results shown in Table 2 were obtained using the Lambard-Bell law.

[Table] As can be seen from Table 2, the same measured values were obtained when using a cell with an optical path length of 10.0 mm and when using a cell with an optical path length of 50.0 mm. In addition, the total amount of nitrate nitrogen and nitrite nitrogen in the seawater measured was approximately 0.3~
It was also found that it was 0.4ppm.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the principle of the present invention, and FIGS. 2 and 3 are diagrams showing the results of an embodiment of the present invention.

Claims (1)

[Claims] 1 Arbitrary wavelengths λ ₂ and λ ₃ of the ultraviolet absorption spectra S ₁ and S ₂ of two standard samples containing the same amounts _of nitrate nitrogen and nitrite nitrogen, respectively; Wavelengths λ 2 _and λ such that the difference between absorbances E ₂₁ and E ₂₂ (E ₂₁ - E ₂₂ ) and the difference between E ₃₁ and E ₃₂ (E ₃₁ - E ₃₂ ) of S ₂ are equal.
Measure the absorbance E ₂ and E ₃ of the standard solution in ₃ ,
On the other hand, similarly for the sample to be measured, the wavelength λ _2
The absorbances E _{′ 2 and E ′ 3} at A method for measuring the total amount of nitrate nitrogen and nitrite nitrogen, characterized by calculating the total amount of nitrogen.