JP3205594B2 - Metal pyrolysis tube for oxygen analysis and its pyrolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pyrolysis tube for oxygen analysis and a pyrolysis method using the same.
More specifically, the present invention relates to an oxygen analysis method in the field of organic element trace analysis, and a new pyrolysis tube and a pyrolysis method using the same for accurately quantifying oxygen elements in organic compounds. And contributes to a wide range from precision analysis in the field of basic organic chemistry to quality control in the organic chemical industry (mainly pharmaceuticals).

[0002]

2. Description of the Related Art As is well known, an oxygen analysis method includes the following.
Many documents have been reported since about 910. These skeletons are heated to 900 to 1300 ° C. in a pyrolysis tube made of a quartz tube or a graphite tube, etc., and the pyrolysis products are transferred to a platinum carbon layer or a carbon black layer. After converting all oxygen compounds to carbon monoxide (CO) and then transferring the CO to the oxide layer and oxidizing it to carbon dioxide (CO ₂ ), the amount of CO ₂ is determined by gravimetric method, coulometry, thermal conductivity This is to detect the content of the oxygen element by detecting by an infrared absorption method or an infrared absorption method.
Several oxygen analyzers based on these basic principles are already commercially available.

However, these conventional oxygen analysis methods have the following problems. <a> In general, the accuracy of the analysis value of the oxygen element is low, and the accuracy cannot be obtained. In particular, a sample having an oxygen content of 10% or less has a large analysis error, which may exceed ± 0.5%. <B> Since the thermal decomposition characteristics differ depending on the type of the organic compound, a difference is detected in the detection sensitivity of the analysis value of oxygen. <C> From an organic compound containing no oxygen element, 1 to
5% oxygen may be detected.

[0004] For the reasons described above, the oxygen analysis method has not been widely used as a daily analysis method even after many years of progress.

[0005]

SUMMARY OF THE INVENTION The inventor of the present invention
In order to establish a daily analytical method with excellent accuracy and accuracy of oxygen elements in organic compounds, detailed basic studies were conducted on conventional oxygen analytical methods. As a result, it was found that all of the above-mentioned problems were caused by the material of the pyrolysis tube and the pyrolysis method.

[0006] Various kinds of pyrolysis tubes made of quartz glass, graphite, metal and the like were manufactured on a trial basis, and the thermal decomposition characteristics of many organic compounds were examined. In addition, the optimal pyrolysis conditions using a graphite crucible, a nickel crucible, a platinum crucible, and the like were evaluated using each pyrolysis tube. The present invention has been completed based on the results of the above research, and has improved the problems of the conventional oxygen analysis method, and is a new pyrolysis tube capable of greatly improving the accuracy and accuracy of the analysis value of oxygen element. And a pyrolysis method.

[0007]

The present invention solves the above-mentioned problems by providing a metal outer tube, a metal lance tube having a sample insertion port inserted into one end of the metal outer tube,
A metal cartridge for oxygen analysis, comprising: a metal cartridge-type reaction tube inscribed in a metal outer tube; and a reaction reagent for generating carbon monoxide filled in the metal cartridge-type reaction tube. Provide a pyrolysis tube.

Further, according to the present invention, without using a graphite crucible or a platinum crucible, an analysis sample is directly introduced into a metal cartridge type reaction tube of the above-described metal pyrolysis tube for oxygen analysis, and the reaction tube is filled. The present invention also provides a method for performing direct catalytic pyrolysis on the surface of a reaction reagent for producing carbon monoxide. That is, as shown in FIG. 1, for example, the metal pyrolysis tube of the present invention is inscribed in a metal outer tube (1) made of nickel or its alloy, platinum or its alloy, molybdenum, tungsten, etc. A metal or alloy metal cartridge type reaction tube (3) is provided, and a small amount of a reaction reagent for producing carbon monoxide (platinum carbon, nickel carbon , carbon black, etc.) (5) is provided in the reaction tube (3). ) Is filled. A filter (4) is disposed on the outlet side of the reaction reagent (5), while a metal or its alloy similar to the above having a sample inlet (6) at one end of the metal outer tube (1). A metal lance tube (2) is inserted.

When this metal pyrolysis tube is used, it is heated to about 1200 to 1350 ° C., more preferably 1300 to 1
The sample is heated to 320 ° C., and the sample wrapped in the metal capsule is introduced from the sample introduction port (6) of the lance tube (2) in a carrier gas stream such as helium. The flow rate of helium is usually about 150 to 250 ml / min, more preferably 1 to 250 ml / min.
90 to 210 ml / min. In addition to helium, argon, nitrogen gas, or the like may be used as a carrier gas, or a mixture thereof may be used. However, helium is more preferred. Although the flow rate of helium is related to the time for one analysis, it may be about 3 minutes in the method of the present invention (rapid analysis method). The sample capsule falls onto the surface of the heated reagent (5) such as platinum carbon or carbon black,
It is instantaneously pyrolyzed and quantitatively produces CO. Furthermore, the generated CO derived from the pyrolysis tube with helium, and transferred to the oxidized tube was converted to CO _2, CO ₂
Is detected to calculate the oxygen content.

[0010]

According to the thermal decomposition tube and the thermal decomposition method of the present invention, the following characteristic operations are realized. <i> Since no quartz tube or graphite tube is used in the pyrolysis system, there is no analysis error due to CO secondary to these tubes, and samples with an oxygen content of 10% or less have excellent accuracy. And accuracy.

<Ii> Thermal decomposition characteristics based on the molecular structure of the sample, by subjecting the sample to catalytic pyrolysis on the surface of a reaction reagent such as platinum carbon or carbon black without pyrolysis in a platinum crucible or graphite crucible, etc. , Various organic compounds can be thermally decomposed and converted to CO under the same conditions. <iii> Accordingly, the detection sensitivity of various organic compounds having an oxygen content of 4% to 5% becomes constant, and the accuracy and precision of the analysis value of the oxygen element are significantly improved.

[0012]

The present invention will be described below in more detail with reference to examples. That is, all of the metal outer tube (1), lance tube (2) and cartridge type reaction tube (3) illustrated in FIG.
(± 2.5 ° C.), and the helium flow rate for transporting the analysis sample was set to 200 ml / min. Then, after 1.5 to 1.7 mg of the organic compound is weighed and sealed in a silver capsule, the platinum for carbon monoxide generation filled and placed in the cartridge type reaction tube (3) from the sample inlet (6) is filled. It was put on the surface of a reaction reagent (5) made of carbon and pyrolyzed. The CO generated in the pyrolysis tube is led out of the metal pyrolysis tube together with He, guided to an oxidation tube and oxidized to CO ₂ ,
The concentration of O ₂ in the organic compound was calculated by detecting the concentration of O ₂ with an infrared absorption detector.

[0013] Oxygen in various organic compounds was analyzed seven times in succession by the above method, and a part of the analysis results is shown in Table 1.

[0014]

[Table 1]

[0015] Table 1 shows the analysis values and the statistics when two kinds of organic compounds such as antipyrine (O = 8.5%) and caffeine (O = 16.48%) were continuously analyzed seven times each. It is shown. Antipyrine (O = 8.5)
%) Has an average oxygen content of 8.542% and an average analysis error of only 0.042%, which is only slightly large. The range of variation is 0.201%, the standard deviation is 0.0707, and the coefficient of variation is 0.1%.
The average oxygen content of caffeine (O = 16.48%) was 16.527% and the average analysis error was 0.08%.
47%, the range of variation is 0.260%, the standard deviation is 0.0858, and the coefficient of variation is 0.5190%.

Therefore, even with antipyrine having an oxygen content of 10% or less, the oxygen content could be measured with good accuracy without any inferiority to caffeine having an oxygen content of 16.48%. Of course, the method of the invention is described in Table 1.
The oxygen content is not limited to the analysis examples shown in Table 1, but is also measured for 20 kinds of organic compounds in addition to the organic compounds shown in Table 1. Excellent analytical values have been obtained.

[0017]

As described in detail above, according to the present invention, since there is no analysis error caused by CO generated from the analytical instrument, regardless of the oxygen content in the organic compound, the oxygen content is particularly 10%. Even in the following, the oxygen element in the organic compound can be quantified with higher precision and accuracy than the conventional method. Further, since the sample is subjected to direct catalytic pyrolysis, various organic compounds can be pyrolyzed under the same conditions and converted to CO without depending on the pyrolysis characteristics based on the molecular structure of the sample. Therefore, the oxygen content is 4% to 5%.
, The detection sensitivity of various organic compounds becomes constant, and the accuracy and precision of the analysis value of oxygen element are remarkably improved. This provides accurate information on the elemental composition of the organic compound.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a metal pyrolysis tube for oxygen analysis of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal outer tube 2 Metal lance tube 3 Metal cartridge type reaction tube 4 Filter 5 Reaction reagent 6 Sample inlet

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 31/12 G01N 31/00

Claims (4)

(57) [Claims] 1. A metal outer tube, a metal lance tube having a sample inlet inserted at one end of the metal outer tube, and a metal cartridge type reaction tube disposed in contact with the metal outer tube. A pyrolysis tube for oxygen analysis, comprising a tube and a reaction reagent for carbon monoxide generation filled in a metal cartridge type reaction tube. 2. The pyrolysis tube for oxygen analysis according to claim 1, wherein the reaction reagent for producing carbon monoxide is either platinum carbon or carbon black. 3. An analytical sample is thermally decomposed to convert an oxygen compound into carbon monoxide. This carbon monoxide is transferred to an oxidation tube, oxidized to carbon dioxide, and its concentration is detected to calculate the oxygen content. In this method, an analysis sample is introduced directly into a metal cartridge type reaction tube of a metal pyrolysis tube for oxygen analysis, and is subjected to direct catalytic pyrolysis on the surface of a carbon monoxide generation reaction reagent filled in the reaction tube. Characteristic pyrolysis method for oxygen analysis. 4. The method according to claim 3, wherein the analysis sample is wrapped in a metal capsule, conveyed by a helium stream, and directly introduced into a metal cartridge type reaction tube.