Method quantitative chromatographic analysis of gas mixtures containing hydrogen isotopes

 

(57) Abstract:

Use: in analytical chemistry for the identification of individual components of complex gas mixtures containing hydrogen isotopes. Objective: to develop a simple method of analysis of complex gas mixtures containing hydrogen isotopes and impurities, reduction of errors of determination of the content components. Effect: simplified the ability to detect simultaneously and hydrogen isotopes and impurities. The inventive initially miss the analyzed gas mixture containing hydrogen isotopes through the chromatographic column, and then a control sample of each isotope of hydrogen and other components separately. Register the signals of the detector thermal conductivity on the chromatograms in the form of undivided peaks of the gas mixture containing hydrogen isotopes, and in the form of individual peaks of each component. The concentration of hydrogen isotopes and impurities is determined by a mathematical formula based content of hydrogen isotopes and impurities from the magnitude of the analytical signal. table 1.

The invention relates to the field of analytical chemistry and can find application in gas chromatography for opredelyonnogo chromatographic analysis of the gas mixture, including the flow of the gas mixture through a chromatographic column with subsequent measurement of the signal detector, in this case, initially measure the change in the flow rate of carrier gas, record the analytical signal in the form of separated peaks of each component of the mixture.with. USSR N 1728796, CL IPC G 01 N 30/86, publ. 23.04.92, bull. N 15).

The known method is quite complicated and a long time due to the need for prior separation of the components of the gas mixture, which complicates its use for separation of components characterized by similar values of the sorption parameters.

The closest to the technical nature of the claimed method is quantitative chromatographic analysis of gas mixtures containing hydrogen isotopes, including flow of the gas mixture containing hydrogen isotopes at temperatures of about - 190oC through the chromatographic column, the separation of mixtures containing hydrogen isotopes with registration signal detector thermal conductivity in the form of individual peaks of each of the isotopes of hydrogen and calculation of the concentrations of the components in accordance with the mathematical formula for conditions nal of Physical Chemistry, 4443, N 1, v. 65, USA, 1155 Sixtechth St., N. W., Washington, DC. 1962)

The disadvantages of this method include the difficulty of its use for the analysis of gas mixtures containing hydrogen isotopes with slight differences in the sorption properties, or arising in connection with it the need to use special conditions for their separation, as well as the inevitable increase in the error due to the lack of ability ensure absolute separation of isotopes. In addition, the problem is complicated by the increasing requirements in this case, the selection of sorbents and their properties (composition, activation energy, and so on).

The problem to which the invention is directed, is to develop a simple method of analysis of complex gas mixtures containing hydrogen isotopes and impurities in normal conditions, using available materials and standard equipment minimum extra dimensions in the construction of chromatographs used in chemical laboratories.

A new technical result achieved when using the proposed method in comparison with the prototype, is to simplify the method by eliminating the need predvaritelniye isotopes of hydrogen, characterized by similar sorption properties, reducing errors in the determination of the concentrations of isotopes and at the same time the possibility of analysis of impurities present.

A new technical result and the task is provided by the fact that in the known chromatographic method for quantitative determination of the gas mixture containing hydrogen isotopes, including flow of the analyzed gas mixture through a chromatographic column with subsequent measurement of the signal detector thermal conductivity and the concentration of the components of the analyzed gas mixture, in accordance with the proposed method, through the chromatographic column is passed sequentially flows of the analyzed gas mixture containing hydrogen isotopes, and then flows equivalent volume control samples of each of the isotopes of hydrogen and samples of other components of the gas mixture separately, and the concentration of the isotopic components and the concentration of impurities is determined by the following mathematical formulas:< / BR>
< / BR>
< / BR>
< / BR>
where C1(C2C3) - total content of impurities in the analyzed gas mixture containing hydrogen isotopes (and, correspondingly, in V. - C2and iteria (protium) in the analyzed gas mixture, %vol.;

h(H2+D2)the total height of the peak of protium and deuterium in the analyzed gas mixture, mm;

hH2(D2)the peak height of the control (100%) of protium (deuterium), mm;

K1, K2, K3, K4- correction factors that take into account the amount of impurities present, respectively, in the analyzed gas mixture containing hydrogen isotopes in the control samples of protium, deuterium and impurities of protium in the sample deuterium.

The essence of the invention is illustrated as follows.

Quantitative chromatographic analysis of gas mixtures containing hydrogen isotopes on the proposed method is based on the study of chromatograms H2and D2without preliminary isotope separation on a chromatographic column, as provided in the prototype and in other traditional methods.

Implementation of the proposed method has become possible due to differences in the coefficients of thermal conductivity of the analyzed isotopes of hydrogen present in the mixtures and experimentally revealed a linear relationship between the concentration of the isotope mixture and signal intensity of a heat conductivity detector (height undivided the differences in the adsorption properties of isotopes, for the quality of their separation had significant lower temperatures (down to - 190oC), which in turn increased requirements adsorbents and was complicated by the known method. In addition, in connection with such initial operations was inevitable errors associated with the possible lack of completeness of the separation of isotopes, difficulty in additional activation of the adsorbent, the need for production use in the analysis of mixtures containing hydrogen isotopes (e.g., protium and deuterium) with known content component.

The inventive method has allowed to eliminate the mentioned disadvantages of the traditional methods due to the parallel analysis of gas mixtures containing hydrogen isotopes and control samples clean analyzed isotopes. In this case, the gas chromatogram of the mixture is recorded signal detector thermal conductivity in the form of common undivided peak of protium and other analyzed isotope that is present in the mixture, and the chromatograms of control samples of individual isotopes recorded peaks of protium and other isotope. To determine the concentration of each isotope in the mixture was a mathematical formula, based on l is aImost was established in the analysis process is equivalent to the control (blank) samples of protium and deuterium, standard mixtures of hydrogen isotopes in the interval of contents: protium (deuterium) in a mixture of from 2 to 98% vol.

Subject selected conditions analysis (helium flow of 60 ml/min, the volume of the sample is 0.06 ml, the column temperature +50oC) the peak of protium, as the peak deuterium, positive, despite the fact that the conductivity at this temperature higher than thermal conductivity of helium and there is a possibility of occurrence of a negative peak of protium, complicating the identification of the isotope.

However, in selected circumstances occurs such dilution samples protium in casinosites that its content in the mixture with (H2+Not) coming in comparative camera detector, is always less than 13% vol. (confirmed by calculation), when the curve of the dependence of thermal conductivity of the mixture with (H2+D2from the composition has a minimum.

The experiment revealed the possibility of using helium as a carrier gas, allowing to realize a relatively high sensitivity determination of the components in the analyzed mixtures provided regulation volume.

The patterns obtained on non-equilibrium mixtures with a low content of mixed form ND (3% of the sum of isotopes), appearing giay quickly balanced at high temperatures and in contact with the catalyst. Experimentally balanced mixtures installed-size corrections in the analysis of isotopic mixtures of different composition: in the field of low concentrations of ND less than 15% vol. the amendment is comparable with the error of the analysis, and therefore its accounting is optional.

For average concentrations ( ~ 50%) systematic error is about 3%vol. Compared with the prototype of the proposed method provides the ability to easily determine simultaneously with the isotopic composition of impurities without additional operations and use additional sorbents and conditions.

This is possible due to the fact that the analytic signals of the analyzed samples containing isotopes and impurities, the proposed method is conducted simultaneously on the same chromatogram for the sequential transmission of gas streams containing these components separately in similar conditions, In the prototype for these purposes would be necessary to match the analyzed impurities conditions and to introduce additional measures for their identification in the sample.

Offer in the way of a mathematical formula allows you to calculate the individual concentration of each isotope, taking into account the 2 share deuterium (protium) in the amount of isotopes analyzed mixture, % by volume

hH2+2) - total height (undivided) peak of protium and deuterium in the analyzed mixture, mm

hH2(h2- peak height of the control (~100%) of protium (deuterium) m

In the particular case of the presence of impurities in the analyzed sample and reference gases of the individual isotopes introduced correction factors K1, K2, K3, K4considering the amount of impurities present, respectively, in the analyzed gas mixture of isotopes, in a pure sample of protium, deuterium and content of protium in pure deuterium;

< / BR>
where C1(C2C3) - total content of impurities in the analyzed sample (and, correspondingly, in V. - C2and in deuterium - C3), vol.%

C4- the content of protium in deuterium (for example, passport data), vol.%

Thus, using the proposed method allows us to simplify the determination of isotopic composition and impurities in complex gas mixtures with lower uncertainty, analysis duration and lower cost of equipment and materials in comparison with the prototype.

Who is the person in the laboratory.

Example 1. The implementation of the method were carried out in laboratory conditions by analysis of samples of the gas mixture containing hydrogen isotopes (protium and deuterium). The analytic signal (used a heat conductivity detector comprising chromatograph "Color" - 4) was carried out in the form of a chromatogram, measuring the height of the undivided peaks of protium and deuterium in the chromatogram of the sample of the analyzed mixture and height of the individual peaks of protium and deuterium in the chromatograms, the equivalent volume of samples of pure isotopes.

The definition of the claimed mathematical formulas (1, 2), which in the absence of impurities in the samples (C1=0, C2=0, C3=0, C4=0 and hence K1=1, K2=1, K3=1, K4=1) have the form:

< / BR>
CH2=100-C2%vol.

To verify the obtained results and confirm implemented with high precision compared with the prototype were analyzed reference mixtures of protium and deuterium in the range of concentrations of 2 to 98% by volume. As the carrier gas used was helium. Volume 3 parallel reference samples of pure isotopes and their mixtures selected from the conditions of equivalence and make up to 0.06 ml when the pressure is amatr 3 mm) mean grain size which is ~ 0.25 to 0,5 mm

The results obtained are presented in table. 1

As can be seen from the table, the error in determining the contents of the components does not exceed ~ 0,1 - 0,4%vol., which is much closer to the actual values of components contents than is achieved in the prototype, where the deviation of the average concentrations (18 - 34 vol.%

0,6%about. The accuracy of the method prototype largely depends on the completeness of the separation of components, which in turn is determined by the special conditions of activation of the sorbents at low temperatures (-190oC) for separating columns.

Especially to that critical conditions for the implementation of the method in the analysis of low concentrations of isotopes, when the errors will be much higher.

Example 2.

To confirm the analysis of complex gas mixtures containing air and other gas impurities, was shot chromatogram of pure protium and deuterium and the analyzed mixture, as in example 1, and then chromatogram of samples of air or other impurities present (CO, CH4to construct a calibration graph for 3 - 5 points for determining the impurity content in the analyzed samples.

Calculation of the content of protium and Deah (C2= 0, C3=0, C4=0 and K2=1, K3=1, K4=1) have the form:

< / BR>
CH2= 100 - C2< / BR>
In the analyzed mixture found in the amount of 5.3%. air and carbon monoxide. The proportional content of protium - 33,7%vol., deuterium 66,3%vol.

Example 3

To confirm the possibility of determining the isotopic composition in the presence of clean control air impurity gases were shot chromatogram as described in example 2. The calculation was made according to formulas 1, 2, which, when C1=0, C4=0 and therefore K1=1, K4=1 have the form

< / BR>
CH2=100-C2,%vol.

In the control samples found air in against a bunch of 3.3%vol., in deuterium - 2%vol. in the analyzed sample is definitely 10,5%vol. of protium and 89.5%. deuterium.

Example 4

In the conditions of example 1 were analyzed by gas mixture using control isotopic gases, contaminated in this experience deuterium-protium. In this case, the concentration of protium in deuterium taken from the nameplate data. The calculations defined components was carried out according to formulas 1, 2, which, when C1=0, C2=0, C3=0 and K1=1, K2=1, K3=1 have the form

< / BR>
CH2= 100-C2%vol.

When the control is
Similarly, conducting calculations by contamination of protium deuterium. On this basis, and taking into account experimental data for examples 1 - 4 we can conclude that the proposed method is confirmed by the analysis of complex mixtures (in this case, mixtures containing hydrogen isotopes and possible admixture of air and other gases with a higher accuracy and more simple measures and calculations than in the prototype that are not entailed to attract more sophisticated equipment and additional materials.

Method quantitative chromatographic analysis of gas mixtures containing hydrogen isotopes, including flow of the analyzed gas mixture through a chromatographic column with subsequent measurement of the signal detector thermal conductivity and the concentration of the components of the gas mixture, characterized in that through the chromatographic column is passed sequentially from the beginning threads of the analyzed gas mixture containing hydrogen isotopes, and then flows equivalent volume control samples of each of the isotopes of hydrogen and samples of other components of the gas mixture separately, and the concentration of the isotopic components and the concentration of impurities determine the maintenance of impurities in the analyzed gas mixture, containing hydrogen isotopes (and, respectively, in V. - C2and in deuterium - C3), vol.%;

WITH4- the content of protium in deuterium, vol.%;

C2(CH2share deuterium (protium) in the analyzed gas mixture, vol.%;

h(H2+D2)the total height of the peak of protium and deuterium in the analyzed gas mixture, mm,

hH2(D2)the peak height of the control (100%) of protium (deuterium), mm,

K1, K2, K3P - correction factors that take into account the amount of impurities present, respectively, in the analyzed gas mixture containing hydrogen isotopes in the control samples of protium, deuterium and impurities of protium in the sample deuterium.

 

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