JP2014182082A - Analytical method and analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analytical method capable of efficiently analyzing a sample, without reducing analysis accuracy and reproducibility of measured values.SOLUTION: The analytical method of the present invention for measuring the content of each component contained in a sample, by burning and decomposing the sample in a reaction tube under the existence of oxygen includes: a first step (Fig. 1(a)) of supplying the sample into the reaction tube, after that, supplying oxygen into the reaction tube and substituting oxygen for gas in the reaction tube; a second step (Fig. 1(b)) of burning and decomposing the sample in the reaction tube to obtain sample gas, and circulating the sample gas in a circulation path; and a third step (Fig. 1(c)) of analyzing a part or the whole of the sample gas in the circulation path, and thereby measuring the content of each component contained in the sample. While the third step is executed for one sample, one of the first step and the second step is executed for another sample different from one sample.

Description

  The present invention relates to an analysis method and an analysis apparatus, and more particularly to an analysis method and an analysis apparatus for measuring the content of nitrogen or nitrogen and carbon in a sample.

  Conventionally, the Kjeldahl method has been used for the analysis of total nitrogen contained in food and feed, but the Kjeldahl method uses concentrated sulfuric acid or alkaline chemicals during the measurement work, so that the working environment is bad, There was a problem that the occupational safety environment was damaged. Therefore, as an alternative to Kjeldahl method, total nitrogen and total carbon measuring devices are attracting attention.

  The total nitrogen / total carbon measuring device has been widely recognized by the market as an official method since it was certified by the Japanese feed analysis standards in 2007, centering on the Japanese Agricultural Standards (JAS Standard). Specific examples of such a measuring apparatus include an analyzer disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 57-84355) and Patent Document 2 (Japanese Patent Laid-Open No. 2003-107071). These analyzers introduce a sample into a reaction tube, supply oxygen, and heat it to produce a sample gas by burning and decomposing the sample, and separating the sample gas with a separation column, The content of each component is detected.

  The total nitrogen / total carbon measuring device to be analyzed in this way has an advantage that the content of each component in the sample can be simultaneously measured safely and easily as compared with the Kjeldahl method. Moreover, since the measured value is not only highly accurate but also highly reproducible, it can be used for analysis in a wide range of fields.

JP-A-57-84355 JP 2003-107071 A

  However, since the total nitrogen / total carbon measuring apparatus takes a long time to measure, it has been desired to be able to measure in a shorter time.

  The present invention has been made in view of the above-described present situation, and an object thereof is to provide an analysis method and an analysis apparatus capable of efficiently analyzing a sample without degrading analysis accuracy and reproducibility of measurement values. It is in.

In order to shorten the time required for the analysis of the measuring apparatus, the inventors have divided a series of procedures from the introduction of a sample into a reaction tube to the detection of each component individually for each process, We examined whether there was room to shorten the work time in each process. However, in order to maintain high measurement accuracy, it has been found that it is difficult to shorten the working time in any process.
Based on this knowledge, each process was further scrutinized, and a plurality of samples were introduced into the apparatus in sequence, and an analysis method that can execute each process in parallel on a plurality of samples was conceived and realized. As a result, it was found that the sample could be analyzed in a short time, and the analysis method of the present invention shown below was completed.

That is, the analysis method of the present invention measures the content of each component contained in a sample by burning and decomposing the sample in a reaction tube in the presence of oxygen, and after supplying the sample into the reaction tube, A first step of supplying oxygen into the reaction tube and replacing the gas in the reaction tube with oxygen; and a second step of obtaining a sample gas by burning and decomposing the sample in the reaction tube and circulating the sample gas in the circulation path A third step of measuring a content of each component contained in the sample by analyzing a part or all of the sample gas in the circulation path, and performing the third step One of the first step and the second step is performed on a sample different from the above.
It is preferable to start the first step on a sample different from the sample on which the third step is executed after or simultaneously with the start of the third step.
It is preferable that a sample different from the sample that has finished the third step has finished the second step after or simultaneously with the completion of the third step.
Including a continuous measurement step for continuously executing the third step. The continuous measurement step is performed after the third step is completed or at the same time as a third sample for a sample different from the sample that has completed the third step. It is preferable that it is the process of starting a step.
In the first step, an inert gas may be introduced together with oxygen.
The sample preferably contains at least nitrogen or carbon.
The analyzer of the present invention includes a reaction tube that generates a sample gas by reacting a sample to be analyzed with oxygen, a circulation path through which the sample gas is circulated, and a measurement unit that measures the content of each component of the sample gas. The sample is measured by the measurement unit and at the same time, a process for reacting a sample different from the sample with oxygen is performed, or the sample gas obtained by reacting the other sample with oxygen is circulated in the circulation path. And a control unit that executes processing to be performed.

  The analysis method and the analysis apparatus according to the present invention have the above-described configuration, so that the analysis accuracy and the reproducibility of the measurement value are high, and the sample can be analyzed in a short time.

(A)-(c) is a schematic diagram which shows operation | movement of the analyzer which applies the analysis method of this invention.

  For convenience of description of the analysis method of the present invention, an example of an analysis apparatus to which the analysis method of the present invention is applied and an outline of an analysis procedure of the analysis apparatus will be described in advance. FIGS. 1A to 1C are schematic diagrams showing the operation of an analyzer to which the analysis method of the present invention is applied.

<Analyzer>
As shown in FIG. 1 (a), the analyzer of the present invention includes a reaction tube 11 for generating a sample gas by reacting a sample 10 to be analyzed with oxygen, a circulation path 15 for circulating the sample gas, The measurement unit 17 that measures the content of each component of the sample gas, and the sample is measured by the measurement unit 17. At the same time, a process for reacting a sample other than the sample with oxygen is performed, or And a control unit (not shown) for executing a process of circulating the sample gas obtained by reacting with oxygen in the circulation path 15. Here, examples of the control unit include a personal computer or software built in the personal computer. By using such an analyzer, the following analysis method can be executed, and the analysis time can be shortened without reducing the analysis accuracy.

<Analysis method>
In the analysis method using this analyzer, referring to FIG. 1A, first, a sample 10 to be analyzed is supplied into a reaction tube 11 from a sample supply port 13. Next, oxygen is supplied from the oxygen cylinder 21 to the reaction tube 11 through the first supply path 12, and the gas in the reaction tube 11 is replaced with oxygen.

  Thereafter, the first flow path switching mechanism 19 (four-way switching valve) is switched to connect the first supply path 12 and the circulation path 15 as shown in FIG. Then, the temperature inside the reaction tube 11 is raised, and the sample is combusted and decomposed together with oxygen. By this combustion decomposition, sample gas and water are generated from the sample and oxygen. Water is removed by the moisture removing unit 22, and the sample gas is supplied to the circulation path 15. The sample gas supplied to the circulation path 15 is circulated using the circulation means 16 (for example, a pump), the circulation path 15, the metering tube 14, the first flow path switching mechanism 19, the first supply path 12, the reaction tube 11, and moisture. It circulates in order of the removal part 22 and the 2nd flow-path switching mechanism 20 (six-way switching valve). By executing this circulation for a certain time, the concentration of the sample gas in the circulation path is made substantially uniform. Thereby, the inside of the measuring tube 14 is filled with the sample gas having a substantially uniform concentration.

  Next, the second flow path switching mechanism 20 is switched to connect the measuring tube 14 and the second supply path 18 as shown in FIG. The sample gas in the metering tube 14 is supplied to the reduction tube 24 through the second supply path 18. After the sample gas is reduced in the reducing tube 24, the content of each component is measured by the measuring unit 17. As described above, the content of each component contained in the sample is measured.

  The analysis method of the present invention measures the content of each component contained in the sample 10 by burning and decomposing the sample 10 in the reaction tube 11 in the presence of oxygen. In the first step of introducing oxygen into the reaction tube 11 and replacing the gas in the reaction tube 11 with oxygen (FIG. 1A), the sample 10 is combusted and decomposed in the reaction tube 11. The sample gas is obtained and the sample gas is circulated in the circulation path 15 (FIG. 1 (b)), and a part or all of the sample gas in the circulation path 15 is analyzed to obtain a sample gas. A third step of measuring the content of each component contained therein (FIG. 1 (c)), and during the execution of the third step, the first step or the second step for a sample different from the sample One of the following is performed.

  The first to third steps are a series of continuous work steps from the introduction of the sample 10 into the reaction tube 11 to the detection of the amount of each component. The process is performed for each sample, and each part of the analyzer is utilized to the maximum. In this way, the idea of separating a series of continuous work processes individually is novel, but in addition to that, the timing of supplying a sample is adjusted in accordance with each process, and another one is required before the analysis of one sample is completed. Also worthy of special mention is the means of supplying one sample, subjecting it to a series of steps for analyzing two samples in parallel, and repeating the measurement in succession.

  In the first place, the conventional commercially available analyzer is to measure the total amount of the sample gas with a detector after burning the sample to generate the sample gas, so that each process as in the first to third steps above. There was no notion of distinction. For this reason, in a conventional commercially available analysis method, after obtaining an analysis result for one sample, a similar series of operations is performed for another sample. That is, in the conventional commercially available analyzer, the sample is supplied one sample at a time, and two samples are not simultaneously supplied into the analyzer.

  On the other hand, in the analysis method of the present invention, the generated sample gas is once stored in the measuring tube 14 and then flowed to the measuring unit 17, so that the individual steps are performed in the first to third steps. Can be divided into Therefore, while the third step is being performed on one sample, either the first step or the second step can be performed on another one sample. That is, it is possible to repeat the measurement continuously by applying a series of steps for analyzing two samples in parallel with one analyzer. Such an analysis technique can shorten the time required for analysis as compared with the conventional analysis method. In addition, since the processing time of each step itself is not shortened, there is an advantage that the analysis accuracy and the reproducibility of the measurement value are not lowered. Hereafter, each step which comprises the analysis method of this invention is demonstrated.

<First step>
The first step is a process of introducing the sample 10 and oxygen into the reaction tube 11. The sample 10 is first supplied into the reaction tube 11 and then oxygen is continuously supplied to replace the gas in the reaction tube 11 with oxygen.

  The sample 10 is supplied to the reaction tube 11 in a state of being put in a sample container. The amount of the sample is not particularly limited, but is generally 10 μl or more and 1000 μl or less when the sample is a liquid, and preferably 0.01 g or more and 2 g or less when the sample is a solid. On the other hand, oxygen is supplied from the oxygen cylinder 21 to the reaction tube 11 via the first supply path 12. The flow rate when supplying oxygen is preferably 2000 ml / min or more and 3000 ml / min or less, and the supply time is usually 30 seconds or more and 120 seconds or less, and preferably 40 seconds or more and 100 seconds or less.

  In addition, when supplying oxygen to the reaction tube 11, an inert gas may be supplied together with oxygen. As the inert gas, helium gas, argon gas or the like is used. When supplying an inert gas together with oxygen, the volume ratio of the mixing ratio of oxygen and inert gas is preferably expressed as “oxygen: inert gas” and is preferably 1: 3 to 3: 1. Is 2: 3 to 3: 2. The reaction tube 11 is preferably made of quartz, and preferably has an inner diameter of 12 mm to 25 mm and a length of 30 cm to 70 cm. The sample preferably contains at least nitrogen or carbon. This is because the analysis method and analysis apparatus of the present invention are excellent in detecting such components.

  After finishing the first step, before starting the second step, the connection of the flow path is switched by the first flow path switching mechanism 19. As a result, a path that circulates through the reaction tube 11, the moisture removing unit 22, the circulation path 15, the measuring pipe 14, the circulation means 16, and the first supply path 12 is formed. The flow path switching in the first flow path switching mechanism 19 is preferably performed by an electromagnetic valve. This is because the switching by the electromagnetic valve contributes to the simplification of the device configuration and can reduce the size of the device itself.

<Second step>
The second step is a step of obtaining a sample gas by burning and decomposing the sample in the reaction tube and circulating the sample gas in the circulation path. Such combustion decomposition is performed by heating the reaction tube 11. The combustion decomposition temperature is preferably 500 ° C. or higher and 1200 ° C. or lower.

  The reaction tube 11 preferably contains a catalyst 23 for promoting combustion decomposition of the sample. The catalyst 23 is preferably one or more selected from the group consisting of copper oxide, silicon oxide, cobalt oxide, selenium oxide and silicate. By including such a catalyst 23, it becomes easy to completely burn the sample, and a trace component in the sample can be detected with high accuracy. In addition, although the said silicon oxide generally means a silicon dioxide, it is not restricted only to this. The silicate is preferably used in the form of quartz cotton or the like. When the catalyst 23 is included in the reaction tube, the length of the portion occupying the catalyst in the reaction tube is preferably 20 cm or more.

  By the combustion decomposition, the sample and oxygen react to generate sample gas and water. Water is removed by the moisture removing unit 22 and only the sample gas is caused to flow through the circulation path 15. The sample gas is flowed by the circulation means 16 in the order of the first flow path switching mechanism 19, the first supply path 12, the reaction tube 11, the moisture removing unit 22, and the circulation path 15. The circulation of the sample gas is preferably 90 seconds or more and 300 seconds or less, more preferably 90 seconds or more and 180 seconds or less, at a flow rate of 2000 ml / min or more and 3000 ml / min or less. By circulating at such a flow rate and time, the concentration of the sample gas flowing through the circulation path can be made substantially uniform.

  After finishing the second step, before starting the third step, the second channel switching mechanism 20 switches the channel connection. Thereby, a path that flows through the measuring pipe 14, the second supply path 18, the reduction pipe 24, and the measurement unit 17 is formed.

<Third step>
The third step is a step of measuring the content of each component contained in the sample by analyzing part or all of the sample gas in the circulation path. Here, a part of the sample gas in the circulation path means a sample gas filled in the measuring tube 14 among the sample gases flowing in the circulation path. That is, all of the sample gas supplied to the measuring tube 14 in the second step is supplied to the measuring unit 17 in this step.

  With this step, the entire amount of the sample gas that fills the measuring pipe 14 is supplied to the reduction pipe 24 via the second supply path 18. The reducing tube 24 is filled with a reducing agent. As such a reducing agent, for example, copper is preferable, and copper processed into a linear or granular form is more preferably used. When using copper, it is preferable to reduce the sample gas by heating to 500 ° C. or more and 600 ° C. or less. The reducing tube 24 preferably has an inner diameter of 5 mm to 15 mm and a length of 15 cm to 40 cm.

  When the sample gas passes through the reduction pipe 24, the oxide in the sample gas is reduced to become a simple substance (may be a compound depending on the composition of the sample gas). Thus, by making the oxide in sample gas into a single substance, and supplying to the measurement part 17, the measured value of each component contained in sample gas can be obtained strictly. The content of each component can be obtained by calculating the measured value with a data processor or the like. It should be noted that the time from the start of supplying the sample gas to the measurement unit 17 until the measurement result is obtained is usually 30 seconds to 600 seconds, and preferably 40 seconds to 300 seconds.

  Although the apparatus used for the measurement part 17 is not specifically limited, It is preferable to use a gas chromatograph from a viewpoint suitable for the detection of simple substance (compound) other than carrier gas. In the gas chromatograph, the change in thermal conductivity caused by the sample gas contained in the carrier gas is detected as a change in resistance value using a Wheatstone bridge circuit, and the content of each component is measured based on this change in resistance value. .

  The material constituting each path is preferably a material that hardly corrodes the sample gas, and specifically, is preferably made of SUS.

  In the analysis method of the present invention, it is preferable to start the first step on a sample different from the sample on which the third step is performed after or simultaneously with the start of the third step. More preferably, the first step is performed on a sample different from the sample on which the third step is performed after the start and before the completion of the third step. By starting the first step at such timing, it becomes possible to analyze the sample continuously, and thus, efficient analysis becomes possible.

  Moreover, it is preferable that a sample different from the sample that has finished the third step has finished the second step after or at the same time as the third step. That is, it is preferable that after the third step is completed for one sample, the third step is started for a sample different from the sample that has completed the third step. By continuously supplying the sample in this way, the third step can be executed continuously, and the analysis result after the second sample in the continuous sample measurement is only the time required for the third step. It can be.

  When analyzing two or more samples, it is preferable to include a continuous measurement step in which the third step is continuously executed. Such a continuous measurement step is a step of starting the third step for a sample different from the sample that has finished the third step after the third step. Of the first to third steps, the most time-consuming step is often the third step. Therefore, in order to efficiently execute the third step, the timing of executing the first step and the second step is adjusted, and when one sample finishes the third step, the next sample is the third step. It is preferable to be in a state where the process can be started. By adjusting the timing of each step in this manner, the third step can be executed continuously, thereby contributing to shortening of the measurement time.

  An example of the continuous measurement step will be described. For example, if the time required for the first step is 50 seconds, the time required for the second step is 100 seconds, and the time required for the third step is 250 seconds, the third step is started for one sample. It is preferable to adjust the sample supply timing such that the first step is started for another sample 100 seconds after the start. By starting the first step at such timing, the timing of the third step end of the first sample coincides with the end of the second step of the second sample, and the third step is continuously performed. Can be executed. By continuously executing the third step in this manner, the sample can be analyzed efficiently, and the temperature in the apparatus is stabilized, so that there is an advantage that the measurement accuracy and the reproducibility of the measurement value can be improved.

  Hereinafter, the analysis method of the present invention will be described based on examples. In addition, this invention is not limited only to these Examples.

Example 1
Using the analyzer having the structure shown in FIG. 1, samples were supplied as follows and 10 samples were continuously analyzed. First, as shown in FIG. 1A, after the sample was supplied into the reaction tube, oxygen was supplied into the reaction tube, and the gas in the reaction tube was replaced with oxygen (first step). Next, the four-way switching valve was switched to the form shown in FIG. Then, the sample was burned and decomposed in the reaction tube to obtain a sample gas, and the sample gas was circulated in the circulation path (second step). Next, the six-way switching valve was switched to the form shown in FIG. Next, the content of each component contained in the sample was measured by analyzing part or all of the sample gas in the circulation path (third step). In Example 1, each step was performed at the following times.
First step: 90 seconds Second step: 200 seconds Third step: 270 seconds

  In this example, at the same time as starting the third step for one sample and simultaneously starting the first step for another sample, 10 samples were continuously supplied. The time required for obtaining the measurement results of 10 samples was 52 minutes and 50 seconds.

(Example 2)
Ten samples were analyzed in the same manner as in Example 1 except that the time of each step and the timing of sample supply differed from Example 1 as described below.
First step: 90 seconds Second step: 150 seconds Third step: 270 seconds

  In this example, the sample was supplied at the timing of starting the first step for another sample 30 seconds after the third step was started for one sample. By supplying the sample in this manner, one sample finishes the third step and another sample finishes the second step, so that the third step is substantially executed continuously. I was able to. The time required to obtain the measurement results of 10 samples was 49 minutes.

(Comparative Example 1)
Ten samples were continuously analyzed in the same manner as in Example 1 except that the analysis was performed using the conventional analysis method. That is, 10 samples were analyzed such that the first step was started for another sample at the same time as the third step was completed for one sample. The time required to obtain the measurement results of 10 samples was 93 minutes and 20 seconds.

(Measurement results and discussion)
When the analysis result obtained using the analysis method of the example was compared with the analysis result obtained using the analysis method of the comparative example, no substantial difference was found between the two. From this, it became clear that the analysis method of the present invention is equivalent in measurement accuracy and reproducibility of measurement values as compared with the conventional analysis method. Further, from the comparison of the time required to obtain the measurement results in Example 1 and Comparative Example 1, the time required for the analysis when the analysis method of the present invention is applied is about the time required for the analysis of the conventional analysis method. The analysis method of the present invention was found to be 57%, and it was revealed that the measurement time can be greatly shortened as compared with the conventional analysis method.

  From these results, it became clear that by using the analysis method of the present invention, the sample can be efficiently analyzed without reducing the analysis accuracy and the reproducibility of the measurement values, and the effect of the present invention was shown. .

  The analysis method of the present invention is suitably used when a large amount of analysis results are required in the analysis of nitrogen and carbon contained in samples such as food, industrial products, soil, plants, manure feed, and pharmaceuticals.

10 Sample 11 Reaction tube 12 First supply path 13 Sample supply port 14 Metering pipe 15 Circulation path 16 Circulating means 17 Measurement unit 18 Second supply path 19 First flow path switching mechanism 20 Second flow path switching mechanism 21 Oxygen cylinder 22 Moisture Removal unit 23 Catalyst 24 Reduction tube

Claims (7)

An analysis method for measuring the content of each component contained in a sample by burning and decomposing the sample in a reaction tube in the presence of oxygen,
A first step of supplying oxygen into the reaction tube after supplying the sample into the reaction tube, and substituting the gas in the reaction tube with oxygen;
A second step of burning and decomposing the sample in the reaction tube to obtain a sample gas, and circulating the sample gas in a circulation path;
A third step of measuring the content of each component contained in the sample by analyzing a part or all of the sample gas in the circulation path, and
During the execution of the third step, either the first step or the second step is performed on a sample different from the sample.   The analysis method according to claim 1, wherein the first step is started on a sample different from the sample on which the third step is executed after or simultaneously with the start of the third step.   The analysis method according to claim 1 or 2, wherein a sample different from the sample that has finished the third step has finished the second step after or simultaneously with the completion of the third step. Including a continuous measurement step of continuously executing the third step,
The said continuous measurement step is a process of starting a 3rd step with respect to a sample different from the sample which finished the said 3rd step after finishing the said 3rd step, or simultaneously with the finishing. The analysis method according to any one of the above.   The analysis method according to claim 1, wherein the first step introduces an inert gas together with oxygen.   The analysis method according to claim 1, wherein the sample contains at least nitrogen or carbon. A reaction tube for generating a sample gas by reacting a sample to be analyzed with oxygen;
A circulation path for circulating the sample gas;
A measuring unit for measuring the content of each component of the sample gas;
At the same time that the sample is measured by the measurement unit, a process for reacting a sample other than the sample with oxygen is performed, or a sample gas obtained by reacting the other sample with oxygen is used as the circulation path. And a control unit that executes a process circulating in the analyzer.

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