JP4849010B2 - Method of burning sample for analysis - Google Patents

Description

  The present invention relates to a method for burning an analysis sample, and more particularly to a method for burning an analysis sample in which a cracked gas obtained by thermal decomposition of a sample is burned and the combustion gas is recovered as a sample gas for analysis. Is.

  For example, in a quantitative analysis of sulfur in a solid sample, a combustion apparatus provided with a heating furnace for pyrolysis and a constant temperature furnace for combustion was used, and the sample was pyrolyzed in the heating furnace. The cracked gas is burned in a constant temperature furnace, and the combustion gas is recovered as a sample gas for analysis. For sulfur, for example, sulfur dioxide in the sample gas is absorbed into the absorption liquid, and the absorption liquid is introduced into an ion chromatograph for analysis.

  As a method for burning an analysis sample using the above-described combustion apparatus, the sample is heated from its melting point to 50 ° C. higher than the melting point by 50 to 180 ° C./min in the heating furnace (vaporization section) for thermal decomposition. There has been proposed a “solid sample decomposition method” in which the decomposition gas obtained is heated at a temperature rising rate and burned in a constant temperature furnace (combustion section) for combustion to recover the combustion gas.

According to the combustion method described above, the conventional combustion depends on the analyst's experience of moving the sample into the heating furnace while keeping the sample close to the inlet of the high-temperature heating furnace and observing the volatilization / decomposition state of the sample. Compared with the method, the sample can be easily burned completely and the target component can be recovered simply by processing according to a preset heating program.
Japanese Patent No. 2781013

  By the way, in the conventional combustion method (solid sample decomposition method), the temperature of the heating furnace is adjusted based on the melting point. In practice, however, the temperature is adjusted to a temperature at which the sample can be efficiently thermally decomposed according to the composition of the sample. It is necessary to accurately set the furnace temperature, and it is necessary to acquire information related to the composition of the sample in advance. In other words, a sample whose component is unknown cannot be immediately analyzed because its melting point and allowable heating range are unknown. For efficient analysis, it is desirable to heat the temperature raising furnace to the target temperature as quickly as possible in the combustion process.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sample combustion method in which a decomposition gas obtained by thermal decomposition of a sample is burned and the combustion gas is recovered as a sample gas for analysis. Therefore, it is an object of the present invention to provide a method for burning an analytical sample that can easily and completely decompose and burn even a sample whose component is unknown, and that can recover the target component more reliably.

  In order to solve the above problems, in the present invention, first, a preliminary sample is heat-treated in a temperature raising furnace. At that time, heating is performed until at least cracked gas is generated, and combustion of the cracked gas is detected in a constant temperature furnace, thereby measuring the temperature of the temperature raising furnace at which the thermal decomposition of the sample starts. Next, this sample is thermally decomposed in a temperature raising furnace, and the obtained decomposition gas is burned in a constant temperature furnace. At that time, the temperature of the heating furnace measured at the time of the heat treatment of the preliminary sample is used as data, and the temperature of the heating furnace is controlled within a temperature range suitable for the thermal decomposition.

  That is, the gist of the present invention is to use a combustion apparatus provided with a heating furnace for thermal decomposition and a constant temperature furnace for combustion, heat decompose the sample in the temperature rising furnace, and use the obtained decomposition gas for the constant temperature furnace. In which the combustion gas is recovered as a sample gas for analysis, wherein the preliminary sample is heated until at least cracked gas is generated in the temperature rising furnace, and the cracked gas in the constant temperature furnace is heated. Detecting the combustion and measuring the temperature of the heating furnace during combustion of the cracked gas, and then thermally decomposing the sample in the heating furnace while controlling the temperature of the heating furnace based on the measured temperature, The present invention relates to a method for burning an analytical sample, characterized by burning cracked gas in a thermostatic furnace.

  According to the method for burning an analytical sample according to the present invention, a preliminary sample is preliminarily heat-treated in a temperature raising furnace, the combustion of cracked gas in the constant temperature furnace is detected, and the temperature of the temperature raising furnace at the start of decomposition of the sample is detected. Since the sample is processed by controlling the temperature of the heating furnace based on the measured temperature, the sample can be easily and completely decomposed and burned even if the component is unknown. The target component can be recovered. In addition, since this sample can be processed immediately at a temperature suitable for thermal decomposition, more efficient analysis can be performed.

  An embodiment of a method for burning an analytical sample according to the present invention (hereinafter abbreviated as “burning method”) will be described with reference to the drawings. FIG. 1 is a side view partially broken away showing the main structure of a combustion apparatus suitable for carrying out the present invention. FIG. 2 is a monitor screen showing the set temperature of the heating furnace when the preliminary sample is processed, the measured temperature change of the heating furnace, and the combustion state of the constant temperature furnace in the analysis of polyethylene as an example. FIG. 3 is a diagram of a monitor screen that displays the set temperature of the heating furnace when the sample is processed, the actually measured temperature change of the heating furnace, and the combustion state of the constant temperature furnace.

  The combustion method of the present invention is applied, for example, when recovering the above components in quantitative analysis of components such as sulfur and halogen contained in an organic sample. The sample may be either a solid sample or a liquid sample. In the present invention, a combustion apparatus as shown in FIG. 1, that is, a combustion apparatus provided with a heating furnace (A1) for thermal decomposition and a constant temperature furnace (A2) for combustion is used. In A1), the sample is thermally decomposed, and the obtained decomposition gas is combusted in an oxygen atmosphere in a constant temperature furnace (A2) to recover the combustion gas as a sample gas for analysis.

  First, the above-described combustion apparatus used in the present invention will be described. The combustion apparatus shown in FIG. 1 is configured to be able to supply a carrier gas and is provided with an inner pipe (1) provided with a heater (2) at a part of the outer peripheral portion, and configured to be able to supply oxygen and to a heater at the outer peripheral portion. An outer tube (4) provided with (5), and a sample supply boat (3) inserted into the inner tube from the proximal end side of the inner tube (1). ) Is inserted concentrically to a substantially central portion of the outer tube (4), and the temperature raising furnace (A1) is composed of an inner tube (1) and a heater (2) for heating the inner tube from the outer peripheral side. The constant temperature furnace (A2) is configured by the outer tube (4) and the heater (5) for heating the outer tube from the outer peripheral side. Usually, the inner tube (1), the outer tube (4) and the boat (3) are made of quartz.

  The inner pipe (1) constituting the temperature raising furnace (A1) is a long axis pipe for guiding the cracked gas generated by the thermal decomposition of the sample to the outer tube (4) of the constant temperature furnace (A2). Is designed to have a length of about 10 to 20 mm and a length of about 200 to 300 mm. The open end (the left end in the figure) of the inner tube (1) is inserted at a position corresponding to the approximate center of the length of the outer tube (4). A carrier gas introduction pipe (81) extended from a carrier gas container through a flow rate controller is connected to the base end (the right end in the figure) of the inner pipe (1). As the carrier gas, an inert gas such as argon or a mixed gas of inert gas and oxygen that does not participate in the reaction is used.

  The heater (2) is disposed in the vicinity of the outer tube (4) of the inner tube (1) exposed from the proximal end portion of the outer tube (4), and is more proximal than the heater (2) of the inner tube (1). A sample insertion port (11) is attached to the side portion (right portion in the figure). As the heater (2), an electric furnace (cylindrical heater) with an output of about 0.5 to 1 kw is usually used in order to heat the sample in a short time. The sample insertion port (11) has a structure in which the outer periphery of an opening provided in a part of the inner tube (1) is covered with a casing with a lid.

  The outer tube (4) is a long-axis tube for forming an oxygen atmosphere, and has an inner diameter of about 25 to 35 mm and a length of about 200 to 400 mm. An oxygen introduction pipe (82) extended from the oxygen container via a flow rate controller is connected to the base end (the right end in the figure) of the outer tube (4). Further, although not shown, the distal end portion (left end portion in the figure) of the outer tube (4) is usually filled with quartz cotton for stabilizing combustion. A combustion gas recovery pipe (83) for supplying combustion gas (sample gas) to, for example, an absorption pipe (not shown), which is one of analytical instruments, is provided at the tip of the outer tube (4). As the heater (5), an electric furnace (cylindrical heater) having an output of about 0.7 to 1.5 kw is usually used in order to reliably burn the cracked gas.

  The sample supply boat (3) has a sample loaded between the sample inlet (11) and the portion corresponding to the heater (2) of the inner tube (1) inside the inner tube (1). Is a small plate that reciprocally moves, for example, is formed in the shape of an elongated box with a shallow flat bottom. The boat (3) is provided at the tip of an operation rod operated by the boat controller (30).

  Specifically, a short-axis columnar metal piece that is loosely fitted to the inner periphery of the inner tube (1) is attached to the proximal end of the operating rod, and the outer periphery of the inner tube (1) It consists of a ring-shaped magnet or electromagnet that fits loosely into the inner tube, and moves linearly by the drive mechanism of the boat controller (30) (for example, a drive mechanism composed of a servo motor, a rack mechanism, etc.) to move the metal piece to a magnetic force The sliding piece (31) to be guided by is arranged. That is, the operation rod of the boat (3) is configured to be movable in the inner pipe (1) following the movement of the sliding piece (31) of the boat controller (30).

  In the present invention, as described later, the preliminary sample is heat-treated in the temperature raising furnace (A1), the combustion of the cracked gas is detected in the constant temperature furnace (A2), and the temperature of the temperature rising furnace (A1) at the time of cracked gas combustion The temperature raising furnace (A1) is provided with a temperature sensor (6) for detecting the temperature of the temperature raising furnace, that is, the temperature of the portion heated by the heater (2) of the inner pipe (1). It is done. The constant temperature furnace (A2) is provided with an optical sensor (7) as combustion detection means for detecting combustion of cracked gas in the constant temperature furnace.

  A thermocouple, a thermistor, or the like is used as the temperature sensor (6). The temperature sensor (6) is disposed on the inner peripheral surface of the heater (2) in the vicinity of the inner tube (1). Further, as the optical sensor (7), a photodiode for measuring the intensity of light is usually used. The optical sensor (7) is disposed at a position close to the outer peripheral surface of the outer tube (4) and substantially corresponding to the tip of the inner tube (1). In the combustion apparatus, the combustion state of the cracked gas in the constant temperature furnace (A2) can be detected by detecting light emission by the optical sensor (7).

  Furthermore, although not shown, as a combustion detection means for cracked gas in the constant temperature furnace (A2), a sensor that measures the carbon dioxide concentration and the oxygen concentration in the sample gas recovered from the constant temperature furnace (A2) can also be used. . That is, when detecting combustion by the carbon dioxide gas concentration, a carbon dioxide gas sensor is provided in the combustion gas recovery pipe (83) of the constant temperature furnace (A2), and decomposition is performed by increasing the carbon dioxide gas concentration in the sample gas (exhaust gas). It is configured to detect gas combustion. In addition, when detecting combustion based on oxygen concentration, an oxygen sensor is provided in the combustion gas recovery pipe (83) of the constant temperature furnace (A2), and combustion of cracked gas is caused by a decrease in oxygen concentration in the sample gas (exhaust gas). It is comprised so that it may detect.

  In the above combustion apparatus, an analysis / control apparatus (9) is provided to perform data analysis and apparatus control. That is, in the combustion device, the analysis / control device (9) determines combustion of cracked gas based on a change in light intensity detected by, for example, a light sensor (7) as combustion detection means, The temperature of the furnace (A1) is held as data, the heater (2) of the temperature raising furnace (A1) and the heater (5) of the constant temperature furnace (A2) are controlled, and further the operation control of the boat controller (30) And supply control of carrier gas and oxygen.

  Further, the analysis / control device (9) is provided with a monitor for displaying the temperature setting of the heating furnace (A1), the temperature of the heating furnace (A1), and the combustion state in the constant temperature furnace (A2) (FIG. 2 and FIG. 3). In addition, the code | symbol (91) in a figure shows the temperature regulator which adjusts the output of a heater (2) and a heater (5).

  Next, the combustion method of the present invention using the above combustion apparatus will be described with reference to FIGS. 2 and 3 as an example of a combustion experiment in component analysis of polyethylene. In the example shown in FIGS. 2 and 3, the combustion of the decomposition gas of the preliminary sample is detected using the optical sensor (7) provided in the constant temperature furnace (A2). In the graphs of FIGS. The broken line indicates the set temperature of the heating furnace (A1), the solid line indicates the temperature of the heating furnace (A1) measured by the temperature sensor (6), and the solid line waveform indicates the constant temperature furnace detected by the optical sensor (7). The combustion state of the cracked gas in (A2) is shown.

  In the present invention, a sample to be processed is distinguished into a preliminary sample and a main sample. As this sample, an amount of sample sufficient for the analysis performed after the combustion process is secured. In the combustion process, first, the preliminary sample is heat-treated until at least cracked gas is generated in the heating furnace (A1). That is, the preliminary sample is heat-treated at least at a temperature equal to or higher than the decomposition temperature. Then, combustion of the cracked gas in the constant temperature furnace (A2) is detected, and the temperature of the temperature raising furnace (A1) at the time of cracked gas combustion is measured.

  Specifically, first, a preliminary sample is placed on the boat (3) waiting at the sample inlet (11), and the boat (3) is moved into the heating furnace (A1) by the boat controller (30). Then, while supplying, for example, argon as a carrier gas to the inner pipe (1) through the carrier gas introduction pipe (81) at a constant flow rate in the range of 150 to 500 ml / min, as shown by the broken line in FIG. The temperature of (A1) is set to a temperature clearly higher than the decomposition temperature of the preliminary sample, for example, 500 ° C., the heater (2) is operated, and the preliminary sample is heated. On the other hand, in the constant temperature furnace (A2), the heater (5) is operated to control the temperature of the constant temperature furnace to a predetermined combustion temperature, for example, 1000 ° C., and to the outer tube (4) through the oxygen introduction pipe (82). Combustion oxygen is supplied at a constant flow rate within a range of 300 to 500 ml / min, for example.

  As shown by the solid line in FIG. 2, when the temperature of the heating furnace (A1) is gradually increased and the preliminary sample of the boat (3) is heated, the decomposition of the sample starts near the decomposition temperature, for example, 300 ° C., The cracked gas is discharged from the tip of the inner tube (1) into the outer tube (4) of the constant temperature furnace (A2). The cracked gas burns in the outer tube (4) of the constant temperature furnace (A2) to which oxygen is supplied.

  In the constant temperature furnace (A2), as shown by the waveform in FIG. 2, the signal output from the optical sensor (7) is in the vicinity of the base value in the initial state where the cracked gas is not released from the inner tube (1). When the cracked gas is released from the inner pipe (1), the output from the photosensor (7) increases rapidly with the emission of light by combustion. Therefore, it is possible to detect the combustion of the cracked gas in the constant temperature furnace (A2) by discriminating the signal of the optical sensor (7). Therefore, the temperature of the heating furnace (A1) when the combustion of cracked gas is detected is measured. In the illustrated preliminary sample, as shown in FIG. 2, it is understood that the temperature raising furnace (A1) reaches about 350 ° C. when combustion is started in the constant temperature furnace (A2).

  Subsequently, after removing the residue of the preliminary sample from the boat (3), the sample is combusted in the heating furnace (A1). In that case, in the present invention, the temperature of the heating furnace (A1) was measured based on the temperature measured as described above in the heat treatment of the preliminary sample, that is, the cracked gas generation temperature (heat decomposition temperature). The temperature is controlled within a range of ± 50 ° C. Then, the sample is thermally decomposed in the heating furnace (A1), and the decomposition gas is burned in the constant temperature furnace (A2).

  Specifically, as in the case of the preliminary sample, the sample is placed on the boat (3) and moved into the heating furnace (A1). Further, as in the case of the preliminary sample, for example, argon is supplied to the inner tube (1) as a carrier gas at a constant flow rate. Then, as shown by the broken line in FIG. 3, the temperature of the heating furnace (A1) is set to approximately the sample decomposition temperature 350 ° C., the heater (2) is operated, and the heating furnace (A1) is rapidly heated. . On the other hand, in the constant temperature furnace (A2), as in the case of the preliminary sample, the heater (5) is operated, the temperature of the constant temperature furnace is maintained at, for example, 1000 ° C., and the outer tube (4) is used for combustion. Supply oxygen at a constant flow rate.

  When the sample is thermally decomposed in the temperature raising furnace (A1), in order to prevent excessive heating, as shown by the broken line in FIG. The temperature of the temperature raising furnace (A1) may be controlled to a temperature, for example, about 300 ° C., and the temperature may be gradually raised while confirming the combustion state of the cracked gas in the constant temperature furnace (A2). In the process illustrated in FIG. 3, the temperature of the heating furnace (A1) is first set in the range of 300 to 310 ° C., and it is confirmed that the sample does not decompose, and then the temperature of the heating furnace (A1) is set to 360. Controlled at ℃.

  With the above temperature setting for the heating furnace (A1), the temperature of the heating furnace (A1) rises rapidly, as shown by the solid line in FIG. When the temperature of the heating furnace (A1) approaches the decomposition temperature (350 ° C.), decomposition of this sample begins, and the decomposition gas flows from the tip of the inner tube (1) to the outer tube (4) of the constant temperature furnace (A2). ) And the cracked gas burns. Combustion in the constant temperature furnace (A2) can be confirmed on the monitor of the analysis / control device (9) by detecting light emitted by the optical sensor (7) as shown by the waveform in FIG.

  In the present invention, the reason for controlling the temperature of the heating furnace (A1) within the range of ± 50 ° C. of the temperature (decomposition start temperature obtained as data) measured in the processing of the preliminary sample during the thermal decomposition of the sample. Is as follows. That is, when the temperature of the heating furnace (A1) is higher than 50 ° C. with respect to the above decomposition start temperature, the sample rapidly decomposes, oxygen is insufficient with respect to the decomposition gas, and incomplete combustion occurs. appear. On the other hand, when the temperature of the heating furnace (A1) is lower than 50 ° C. with respect to the above decomposition start temperature, the thermal decomposition of the sample does not proceed rapidly, and the target component cannot be recovered in the same manner. Therefore, the temperature of the temperature raising furnace (A1) needs to be controlled to at least the above range, and in order to perform the thermal decomposition more reliably, the temperature is lower by 50 ° C. than the decomposition start temperature and higher by 50 ° C. than the decomposition start temperature. It is preferable to raise the temperature gradually to the temperature.

  When the combustion of this sample is almost completed, the temperature of the heating furnace (A1) is set high, for example, to about 700 ° C. as shown by the broken line in FIG. 3, and the temperature of the heating furnace (A1) is further increased. The residue of this sample in the boat (3) is completely decomposed. Thereby, this sample can be decomposed | disassembled completely and all the target components can be collect | recovered. Note that the combustion gas obtained by the combustion treatment in the constant temperature furnace (A2) is taken out through the combustion gas recovery pipe (83), and used for subsequent analysis using ion chromatography or titration.

  As described above, in the present invention, the preliminary sample is heated in advance until at least cracked gas is generated in the temperature raising furnace (A1), and combustion of the cracked gas in the constant temperature furnace (A2) is detected to decompose the sample. After measuring the temperature of the heating furnace (A1) at the start, the sample is subjected to thermal decomposition and combustion treatment while controlling the temperature of the heating furnace (A1) within a specific range suitable for thermal decomposition. Therefore, even a sample whose component is unknown can be easily and completely decomposed and burned, and the target component can be recovered more reliably. In other words, a sample with unknown components can be easily processed without the need for skilled analysis techniques. Moreover, since this sample can be processed immediately at a temperature suitable for thermal decomposition, it can be processed more quickly.

  In the present invention, as described above, in detecting the combustion of the decomposition gas of the preliminary sample in the constant temperature furnace (A2), carbon dioxide gas or oxygen may be detected instead of light. When combustion is detected by carbon dioxide, it is exhausted from the outer tube (4) of the constant temperature furnace (A2) by a carbon dioxide sensor (not shown) provided in the combustion gas recovery pipe (83) of the constant temperature furnace (A2). It is possible to detect a rapid increase in the concentration of carbon dioxide in the gas to detect the combustion of the cracked gas. When combustion is detected by oxygen, the oxygen sensor (not shown) provided in the combustion gas recovery pipe (83) of the constant temperature furnace (A2) is exhausted from the outer tube (4) of the constant temperature furnace (A2). By detecting a rapid decrease in oxygen in the gas, combustion of the cracked gas can be detected.

1 is a side view showing a main structure of a combustion apparatus suitable for carrying out the present invention in a partially broken view. In analysis of polyethylene as an example, it is the figure of the monitor screen which displayed the preset temperature of the heating furnace at the time of processing a preliminary sample, the temperature change of the actually measured heating furnace, and the combustion state of a constant temperature furnace. In analysis of polyethylene as an example, it is the figure of the monitor screen which displayed the preset temperature of the heating furnace at the time of processing this sample, the temperature change of the actually measured heating furnace, and the combustion state of the constant temperature furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Inner pipe | tube 11: Sample insertion port 2: Heater 3: Boat 30: Boat controller 31: Slide piece 4: Outer tube 5: Heater 6: Temperature sensor 7: Light sensor (combustion detection means)
81: Carrier gas introduction pipe 82: Oxygen introduction pipe 83: Combustion gas recovery pipe 9: Analysis / control device (computer)
91: Temperature controller A1: Temperature raising furnace A2: Constant temperature furnace

Claims (4)

  Using a combustion device equipped with a heating furnace for pyrolysis and a constant temperature furnace for combustion, the sample is thermally decomposed in the temperature rising furnace, and the resulting cracked gas is burned in the constant temperature furnace to analyze the combustion gas A method for burning an analytical sample to be recovered as a sample gas for heating, wherein the preliminary sample is heat-treated until at least cracked gas is generated in the heating furnace, and the combustion of the cracked gas in the constant temperature furnace is detected and cracked gas combustion is performed. Measure the temperature of the heating furnace at the time, and then thermally decompose the sample in the heating furnace while controlling the temperature of the heating furnace based on the measured temperature, and burn the cracked gas in the constant temperature furnace A method for burning an analytical sample.   The combustion method according to claim 1, wherein combustion of cracked gas is detected by an optical sensor provided in a constant temperature furnace.   The combustion method according to claim 1, wherein combustion of cracked gas is detected by a carbon dioxide sensor provided in a combustion gas recovery pipe of a constant temperature furnace.   The combustion method according to claim 1, wherein combustion of cracked gas is detected by an oxygen sensor provided in a combustion gas recovery pipe of a constant temperature furnace.

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