Element analysis method, element analysis device, and storage medium

Abstract

The present application relates to an elemental analysis method, an elemental analysis device, and a storage medium. In order to provide an elemental analysis method capable of shortening the time required for elemental analysis and maintaining the precision of zero-point correction equivalent to that of the past, a sample charged into a crucible is heated in a heating furnace, the amount of elements contained in gas derived from the heating furnace is measured by an analysis mechanism, and the elements contained in the sample are analyzed, the elemental analysis method including: a blank measurement step of measuring the amount of elements contained in gas derived from the heating furnace in a case where only the crucible is heated; and a zero-point correction amount is set based on the measurement value in a transition state region where the measurement value rises in blank data obtained in the blank measurement step.

Description

Technical Field

[0001] The present invention relates to an elemental analysis apparatus for analyzing elements contained in a sample based on a sample gas generated by heating a sample contained in a crucible. Background Technology

[0002] To quantify elements such as nitrogen (N), hydrogen (H), and oxygen (O) contained in a sample, an elemental analysis apparatus is used (see Patent Document 1). This apparatus uses a pair of electrodes to hold a graphite crucible containing the sample within a heating furnace, allowing an electric current to flow directly through the crucible to heat both the crucible and the sample. The sample gas generated by heating is then extracted from the furnace and the concentration of various components is determined using an analytical mechanism consisting of an NDIR (Non-Dispersive Infrared) analyzer and a TCD (Thermal Conductivity Detector).

[0003] In the case of the elemental analysis described above, the crucible is heated and degassed by passing an electric current through it for a specified time before the analysis. This is to remove atmospheric components contained in the crucible, as well as compounds of nitrogen, hydrogen, and oxygen contained in the crucible itself, and to suppress the generation of gases that are not from the sample and are not the target gases.

[0004] However, it is difficult to completely eliminate the generation of non-analyte gases from the crucible through degassing. Therefore, even if the flow path is switched after degassing to allow the gas from the heating furnace to be introduced into the analytical apparatus from the exhaust channel and transferred to the actual elemental analysis, such as... Figure 9 As shown, a predetermined standby time is also set, during which current is flowed through the crucible for a specified period, and the amount of gas generated from the crucible is allowed to stabilize. Furthermore, after confirming that the amount of the element measured by the analytical apparatus has increased from the flow channel switching point and stabilized at a substantially constant value, the sample is introduced into the crucible. Additionally, the average value of the analytical apparatus's measurements after the amount of non-analytical gas generated from the crucible has stabilized is set as the zero-point correction value, used to zero-point correct the original data. More specifically, depending on the combustion characteristics of the sample, although there may be variations, the zero-point correction value is, for example, set as the average value between 10 seconds after a predetermined standby time from the time the sample is introduced.

[0005] The time required for the generation of the non-analyte gas from the crucible to stabilize at a roughly constant value can sometimes be as long as one minute, starting from the end of the transitional phase of the measured value's rise. Therefore, it takes time to introduce the sample into the crucible, generate the sample gas, and begin the actual analysis. Furthermore, if the generation of the non-analyte gas varies during the sampling period for calculating the zero-point correction, the zero point will shift, leading to a decrease in analytical accuracy.

[0006] Patent Document 1: Japanese Patent No. 4560058 Summary of the Invention

[0007] The present invention was made in view of the above-mentioned problems, and its object is to provide an elemental analysis method that can shorten the time required for elemental analysis and maintain the accuracy of zero-point correction as in the past.

[0008] That is, the elemental analysis method of the present invention heats the sample placed in the crucible in a heating furnace, and the analysis mechanism determines the amount of elements contained in the gas exiting from the heating furnace, and analyzes the elements contained in the sample. The elemental analysis method includes: a blank determination step, which determines the amount of elements contained in the gas exiting from the heating furnace when only the crucible is heated; and a zero-point correction setting step, which sets a zero-point correction amount based on the measured value in the transition state region where the measured value rises in the blank data obtained in the blank determination step.

[0009] Furthermore, the elemental analysis apparatus of the present invention includes: a heating furnace for heating a sample placed in a crucible; and an analysis mechanism for measuring the amount of elements contained in a gas discharged from the heating furnace. The elemental analysis apparatus analyzes the elements contained in the sample. The elemental analysis apparatus includes: a blank measurement result storage unit for storing the amount of elements contained in the gas discharged from the heating furnace as blank data, measured by the analysis mechanism when only the crucible is heated; and a zero-point correction unit for setting a zero-point correction amount based on the measurement value in the transition state region where the measured value rises in the blank data.

[0010] If this method is used, the zero-point correction is set based on the measured values ​​in the transition region, thus eliminating the need to wait until the measured values ​​of the blank data stabilize to approximately constant values, as was previously required. Therefore, the data needed to determine the zero-point correction can be obtained in a shorter time than before. Furthermore, since the zero-point correction can be set using the same reference as in the blank measurement step during the actual sample placement in the crucible, the time for starting sample gas generation can be advanced without waiting until the measured values ​​stabilize to approximately constant values. Therefore, the overall time required for elemental analysis can be significantly reduced.

[0011] Furthermore, the inventors of this application conducted dedicated research and first discovered that the analytical accuracy does not differ significantly whether the zero-point correction is determined by the measured value of the transition state region or by the measured value of the stable, approximately constant state, as is common practice. That is, it is generally accepted that the amount of non-analyte gas generated from the crucible in the transition state is unstable, resulting in a deviation in the zero-point correction for each analysis and significantly lower analytical accuracy. However, even though the measured value in the transition state actually varies for each analysis, the waveform of the transition state region remains approximately similar in shape for each analysis, exhibiting high reproducibility. Therefore, it is believed that even when using the measured value of the transition state region to determine the zero-point correction, the analytical accuracy is the same as when using the zero-point correction set by the measured value of the stable state.

[0012] In order to make the zero-point correction amount close to the value of the zero-point correction amount set in the past when the measured value of the analytical institution is stable at a substantially constant value, it is preferable to set the zero-point correction amount based on a plurality of measured values ​​in a region where the time derivative of the measured value in the transition state region becomes a slope that decreases.

[0013] The slope reduction region, which can suppress the deviation of the zero-point correction and improve the accuracy of analysis, can be exemplified by the following: the slope reduction region is the region during a predetermined time period starting from the moment when the peak value is taken in the differential blank data obtained by time differentiation of the blank data.

[0014] In order to set the zero-point correction amount related to the measured value of each element to an appropriate value even when the elemental analysis apparatus is configured to analyze multiple elements, it is preferable that the analysis mechanism has multiple analyzers arranged sequentially from upstream to downstream on the outlet flow channel of the gas exiting the furnace, and that the zero-point correction amount is set independently for each analyzer based on the slope reduction region that appears at different times.

[0015] The region of reduced slope that appears in the analyzer located on the upstream side of the analytical apparatus is a region that occurs within a time period of 7 to 20 seconds from the start of the measurement of the blank data. If the zero-point correction is set based on the measured value of such a region, the same analytical accuracy as before can be achieved, and the time to put in the sample and start the actual analysis can be significantly shortened.

[0016] The slope reduction region appearing in the analyzer located further downstream than the analyzer positioned at the upstream end can be defined as the region that appears after a predetermined delay time, using the slope reduction region appearing in the analyzer at the upstream end as a reference. For example, if a delay time is preset based on the separation distance between each analyzer, the volume of the analyzer and the flow channel, and the time required for the gas to be analyzed to arrive, then the slope reduction region appearing in each analyzer can be defined according to the start time of the blank data measurement and the timing of the slope reduction region appearing in the analyzer at the upstream end, and an appropriate zero-point correction amount can be easily set separately.

[0017] As a preferred definition of the slope reduction region that can shorten the time required for elemental analysis while maintaining analytical accuracy, the slope reduction region is the region from the moment when the slope becomes a peak in the differential blank data obtained by time differentiation of the blank data to the moment when it is reduced to 10% of the peak value.

[0018] To reduce the influence of electrical noise and other factors overlapping with the blank data, and to minimize deviations caused by changes in the amount of non-target gas generated from the crucible, it is preferable that the zero-point correction is the average of four consecutive measurements within the slope reduction region of the blank data. If it is a four-point measurement, vibrational components such as electrical noise can easily cancel out errors in the positive and negative directions, thus improving the reproducibility of the zero-point correction.

[0019] To reduce the waiting time required for zero-point correction even when the sample is placed in a crucible for elemental analysis, examples include: a sample determination step that measures the amount of elements contained in the gas extracted from the furnace while the crucible and the sample are heated; and a sample data generation step that sets a zero-point correction amount based on the measured values ​​in the transition region of the measured values ​​obtained in the original data obtained in the sample determination step, and calculates the sample data obtained by zero-point correction of the original data using the zero-point correction amount.

[0020] To prevent the analytical unit from saturating due to the gas generated from the crucible during the blank determination step and to improve the accuracy of elemental analysis, it is preferable to further include a blank firing step, in which only the crucible is heated, and the gas generated from the crucible is discharged to the exhaust channel instead of being introduced into the analytical unit. The blank determination step is initiated by switching the destination of the gas generated from the crucible from the exhaust channel to the analytical unit during or after the blank firing step.

[0021] In order to achieve the same effect as the elemental analysis apparatus of this invention in existing elemental analysis apparatuses, for example by updating the program, the following elemental analysis apparatus program can be used. The elemental analysis apparatus is programmed to include: a heating furnace for heating a sample placed in a crucible; and an analysis mechanism for measuring the amount of elements contained in a gas exiting from the heating furnace. The elemental analysis apparatus analyzes the elements contained in the sample. The program enables a computer to function as a blank measurement result storage unit, a sample gas measurement result storage unit, and a zero-point correction unit. The blank measurement result storage unit stores the amount of elements contained in the gas exiting from the heating furnace as measured by the analysis mechanism when only the crucible is heated, as blank data. The sample gas measurement result storage unit stores the amount of elements contained in the gas exiting from the heating furnace as measured by the analysis mechanism when both the crucible and the sample are heated, as raw data. The zero-point correction unit calculates sample data obtained by zero-point correction of the raw data based on the blank data. The zero-point correction unit sets a zero-point correction amount based on the measurement values ​​in the transition region where the measured values ​​rise in the blank data.

[0022] In addition, the program used in the elemental analysis device can be an electronically published program or a program stored on a program storage medium such as a CD, DVD, or flash memory.

[0023] Thus, the elemental analysis method of the present invention sets the zero-point correction amount based on the measured values ​​of the transitional state region in the blank data. Therefore, compared with the conventional method of setting the zero-point correction amount after waiting until the system reaches a stable state, the waiting time can be significantly shortened. Moreover, the deviation of the zero-point correction amount and the analysis accuracy can be kept approximately equivalent to those of conventional methods. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the structure of an elemental analysis apparatus according to one embodiment of the present invention.

[0025] Figure 2 This is a functional block diagram of an elemental analysis device implemented in the same way.

[0026] Figure 3 This is a schematic diagram illustrating an example of the operation of an elemental analysis apparatus of the same embodiment from the start to the end of elemental analysis, as well as an example of the change in measured values.

[0027] Figure 4 It is a graph showing the definition of each region of blank data in the same implementation method and the coordinates of the sampling points used to calculate the zero-point correction.

[0028] Figure 5It is a coordinate graph showing the zero-point correction results of different crucibles in the same implementation.

[0029] Figure 6 It is a coordinate graph showing the zero-point correction results of each zero-position adjustment time in the same implementation method.

[0030] Figure 7 It is a coordinate graph showing the relationship between the zero-position adjustment time and the deviation of the correction result in the same implementation method.

[0031] Figure 8 It is a coordinate graph representing the differential blank data of the same implementation method.

[0032] Figure 9 This is a schematic diagram illustrating the operation of an elemental analysis apparatus using conventional methods from the start to the end of elemental analysis, as well as the changes in measured values.

[0033] Explanation of reference numerals in the attached figures

[0034] 100 elemental analysis apparatus

[0035] 3 Heating Furnace

[0036] AM Analysis Agency

[0037] C1 Blank Measurement Results Storage Department

[0038] C2 Zero Point Correction Unit

[0039] C3 Sample Gas Measurement Results Storage Department

[0040] C4 Activation Timing Control Department

[0041] C5 Sample Data Storage Unit

[0042] C6 Element Calculation Section Detailed Implementation

[0043] An elemental analysis apparatus 100 according to one embodiment of the present invention will be described with reference to the figures. Figure 1 The diagram shows an outline of an elemental analysis apparatus 100 according to one embodiment.

[0044] The elemental analysis apparatus 100 heats and melts a sample, such as a metal sample or a ceramic sample (hereinafter referred to as the sample), contained in a graphite crucible MP, and analyzes the sample gas generated during this process to determine the amount of elements contained in the sample. In the first embodiment, C (carbon), H (hydrogen), and N (nitrogen) contained in the sample are the elements to be measured.

[0045] like Figure 1As shown, the elemental analysis apparatus 100 includes: a heating furnace 3 for heating a sample contained in a crucible MP; an inlet channel L1 for introducing a carrier gas into the heating furnace 3; an outlet channel L2 for discharging a mixture of the carrier gas and the sample gas from the heating furnace 3; and an exhaust channel L3, branched by a switching valve V, which is disposed in the outlet channel L2 between a dust filter 4 and an analysis unit AM. More specifically, the elemental analysis apparatus 100 comprises a heating furnace 3, various devices disposed in the inlet channel L1 or the outlet channel L2, and a control and calculation unit COM responsible for controlling each device and processing the concentrations measured, etc. The control and calculation unit COM is, for example, a computer equipped with a CPU, memory, an A / D converter, a D / A converter, and various input / output devices, which executes a program for the elemental analysis apparatus stored in the memory to enable the various devices to cooperate and thereby perform its functions. Figure 2 The functions of each part shown in the functional block diagram are as follows. In addition, the control calculation mechanism COM also functions as the display unit (not shown) described later. The display unit displays, for example, the concentration of various elements contained in the sample based on the output of each analyzer that constitutes the analysis mechanism AM, namely the CO detection unit 5, CO2 detection unit 7, H2O detection unit 8, and N2 detection unit 11, which are installed on the outlet flow channel L2.

[0046] Each part is explained in detail.

[0047] like Figure 1 As shown, a gas storage cylinder serving as a carrier gas supply source 1 is connected to the base end of the inlet channel L1. In the first embodiment, He (helium) is supplied into the inlet channel L1 from the supply source 1. Furthermore, a purifier 2 is provided on the inlet channel L1 to remove trace amounts of hydrocarbons contained in the carrier gas, thereby improving the purity of the carrier gas.

[0048] The purifier 2 is formed of a material that physically adsorbs hydrocarbons contained in the carrier gas but does not substantially adsorb the carrier gas itself. Furthermore, the material forming the purifier 2 does not chemically react with the carrier gas or hydrocarbons. That is, the purifier 2 can be, for example, used in gas chromatography, and the material forming the purifier 2 can be, for example, a zeolite-based molecular sieve. Alternatively, the material forming the purifier 2 can also be silica gel, activated carbon, caustic soda asbestos, etc. The purifier 2 can regenerate its adsorption capacity, for example, by heating to desorb the adsorbed molecules.

[0049] The heating furnace 3 is configured to hold a graphite crucible MP containing a sample by clamping it with a pair of electrodes, and to allow current to flow directly through the crucible MP to heat the crucible MP and the sample. When heating the sample, the pressure of the carrier gas is adjusted by a pressure regulating valve (not shown) located on the upstream side of the heating furnace 3, so that the pressure inside the heating furnace 3 is 60 kPa or less, more preferably 40 kPa or less.

[0050] Next, the devices installed on the outlet flow channel L2 will be described.

[0051] On the outlet flow channel L2, starting from the upstream side, a dust filter 4, a switching valve V, a CO detection unit 5, an oxidizer 6, a CO2 detection unit 7, an H2O detection unit 8, a removal mechanism 9, a mass flow controller 10, and an N2 detection unit 11 (which serves as a thermal conductivity analyzer) are arranged sequentially. In this embodiment, all the devices installed on the outlet flow channel L2 except for the dust filter 4 and the switching valve V constitute the analysis unit AM, which measures the amounts of nitrogen, hydrogen, and oxygen, the elements to be analyzed. That is, the analysis unit AM has multiple analyzers on the outlet flow channel L2 from the upstream to the downstream side, and each analyzer is set with an independent zero-point correction value.

[0052] The dust filter 4 filters and removes dust and other contaminants from the gas discharged from the heating furnace 3.

[0053] The switching valve V is a so-called three-way valve, for example, whose connection direction is controlled by a control arithmetic unit COM. This switching valve V switches the flow path so that gas exiting the heating furnace 3 flows either into the exhaust channel L3 or the analytical unit AM, which is located downstream of the switching valve V in the exit channel L2. More specifically, gas generated during the period when only the crucible MP is placed in the heating furnace 3 and is being fired without load, and high-concentration components are being extracted from the crucible MP, flows into the exhaust channel L3. Here, "high concentration" refers to a state where the measured value of the analytical unit AM is saturated or close to saturation. During the period of high-concentration component extraction from the crucible MP, the upstream side of the exit channel L2 in the switching valve V is connected to the exhaust channel L3, and the analytical unit AM side of the exit channel L2 in the switching valve V is closed.

[0054] Furthermore, when the dry firing of crucible MP has been fully completed, and only a low concentration of components is extracted from crucible MP, switching valve V is switched to introduce the gas discharged from heating furnace 3 into analytical unit AM. After a predetermined time has elapsed since switching valve V, the measured value of analytical unit AM begins to rise from zero.

[0055] The CO detection unit 5 consists of an NDIR (non-dispersive infrared gas analyzer) that detects CO (carbon monoxide) in the mixed gas that has passed through the dust filter 4 and determines the CO concentration. From a measurement accuracy perspective, this CO detection unit 5 operates effectively even when the oxygen concentration inside the sample is high. Specifically, it is preferable to use CO concentrations of 150 ppm or higher as the measurement target.

[0056] The oxidizer 6 oxidizes the CO and CO2 contained in the mixed gas that has passed through the CO detection unit 5, and oxidizes H2 to H2O (water) and generates water vapor. In the first embodiment, the oxidizer 6 uses copper oxide, and the temperature of the oxidizer 6 is maintained at a temperature below 450°C by using heating resistors placed around the oxidizer 6.

[0057] The CO2 detection unit 7 is an NDIR (Normally Induced Detection and Reduction) unit that detects CO2 in the mixed gas after passing through the oxidizer 6 and measures the concentration of CO2. From the viewpoint of measurement accuracy, the CO2 detection unit 7 operates effectively when the oxygen concentration in the sample is low (e.g., less than 150 ppm).

[0058] The H2O detection unit 8 is an NDIR (Normally Induced Radiated IR) unit that detects H2O in the mixed gas after passing through the CO2 detection unit 7 and measures the concentration of H2O. Furthermore, the flow path from the oxidizer 6 to the H2O detection unit 8 is configured to maintain the temperature of the mixed gas above 100°C and keep the H2O in a water vapor state. Thus, measurement errors caused by condensation do not occur in the H2O detection unit 8.

[0059] The removal mechanism 9 adsorbs and removes CO2 and H2O contained in the mixed gas. The removal mechanism 9 is composed of an adsorbent, for example, using the same component as the aforementioned purifier 2 provided in the inlet channel L1.

[0060] The mass flow controller 10 is a flow control device that integrates a flow sensor, a control valve, and a flow controller into a single unit. This mass flow controller 10 supplies a mixed gas to the downstream N2 detection unit 11 to maintain a constant flow rate. Therefore, even if the pressure of the mixed gas fluctuates due to the removal mechanism 9, the pressure of the mixed gas in the N2 detection unit 11 can be maintained at a value suitable for measurement. In the first embodiment, the mass flow controller 10 is configured to operate at pressures below 60 kPa, for example, even if the pressure difference before and after is 20 kPa, thereby maintaining the pressure inside the heating furnace 3 at 60 kPa.

[0061] The N2 detection unit 11 is a TCD (thermal conductivity detector) that measures the concentration of a predetermined component, namely N2, in the mixed gas based on the change in the thermal conductivity of the mixed gas and the flow rate of the supplied mixed gas. That is, since the mixed gas supplied to the N2 detection unit 11 consists essentially only of carrier gas and N2, the concentration of N2 in the mixed gas corresponds to the measured change in thermal conductivity. Furthermore, in the first embodiment, no flow meter is provided downstream of the N2 detection unit 11, and the downstream side of the N2 detection unit 11 is directly connected to the exhaust port of the outlet flow channel L2.

[0062] Next, details of the control and calculation mechanism COM will be explained. For example... Figure 2As shown, the control and calculation mechanism COM functions at least as the blank measurement result storage unit C1, the sample gas measurement result storage unit C3, the zero-point correction unit C2, the sample data storage unit C5, the input timing control unit C4, and the element quantity calculation unit C6. The structure of each of these parts will be explained together with the operations from the start to the end of the analysis.

[0063] The elemental analysis performed by the elemental analysis apparatus 100 in this embodiment consists of at least three steps, such as an air-firing step, a blank determination step, and a sample determination step.

[0064] In the dry-firing step, the crucible MP is dry-firing, and the high-concentration components originating from the crucible MP, which are drawn from the heating furnace 3, are discharged through the exhaust channel L3. During the dry-firing step, the switching valve V is used to prevent the gas drawn from the heating furnace 3 from entering the analysis unit AM.

[0065] Starting from the initial dry-fire step, the blank measurement step begins at the point when only low concentrations of components can be extracted from the crucible MP. More specifically, after a predetermined time has elapsed since the start of the dry-fire step, the blank measurement step begins by switching the gas flow from the heating furnace 3 through the exhaust channel L3 to the analyzer AM. The timing of the switch from the dry-fire step to the blank measurement step can be determined in advance through experiments, for example, by calculating the elapsed time until only components below a predetermined concentration can be extracted from the crucible MP, and then set based on the measured elapsed time. In this blank measurement step, the time-series data of the measured values ​​obtained from the CO detection unit 5, CO2 detection unit 7, H2O detection unit 8, and N2 detection unit 11 of each analyzer serving as the analyzer AM, i.e., the blank data, is stored in the blank measurement result storage unit C1, and the zero-point correction amount of the measured values ​​is set based on this blank data. Here, the point at which each blank data is switched from the aforementioned exhaust channel L3 to the analyzer AM is taken as the start point of the blank data measurement. Therefore, in the blank measurement data output from the CO detection unit 5 located at the upstream side, the measurement value rises at the earliest point in time. The rise in the blank data of each analyzer located downstream will produce a delay corresponding to the separation distance relative to the CO detection unit 5 located at the upstream side, and the volume of the equipment and flow channel up to the CO detection unit 5.

[0066] After the blank determination step is completed, crucible MP is removed from furnace 3 and a new crucible MP is placed. The aforementioned blank firing step is performed on this new crucible MP, and the sample determination step begins when only a low concentration of the component can be extracted from crucible MP. That is, the sample determination step is also started by switching the gas flow from furnace 3 from exhaust channel L3 to the analyzer AM side. In this embodiment, as... Figure 3As shown, in the sample measurement step, during the predetermined time period after the gas flow is switched to the AM side of the analyzer, no sample is introduced; only the crucible MP is heated. The timing of sample introduction can be appropriately changed according to the ease of combustion and melting of the sample. In the sample measurement step, the measured value obtained by the AM analyzer is stored as raw data in the sample gas measurement result storage unit C3, and zero-point correction is performed using the zero-point correction amount set in the blank measurement step.

[0067] Next, the setting of the zero-point correction amount and the zero-point correction will be explained in detail. In the blank measurement step, an electric current is applied to the crucible MP while it is contained only in the heating furnace 3, and only the crucible MP is heated. By heating the crucible MP, the atmospheric components contained in the crucible MP, as well as nitrogen, hydrogen, oxygen, etc., which are present in the form of compounds, are degassed, and a small amount of non-analytical gases that do not originate from the sample are extracted. Furthermore, the amount of each element contained in the non-analytical gas discharged from the heating furnace 3 to the discharge channel L2 is measured using the analytical instrument AM, and the data is stored as blank data in the blank measurement result storage unit C1.

[0068] The zero-point correction unit C2 sets the zero-point correction amount based on the measured values ​​in the transition state region where the measured values ​​are rising, from the blank data of each analyzer corresponding to each element (nitrogen, hydrogen, and oxygen). In this embodiment, in particular, the zero-point correction amount is set based on the average of multiple measured values ​​in the slope-decreasing region where the rate of change of time in the transition state region tends to decrease. Furthermore, regarding the timing of the slope-decreasing region appearing in the blank data output by each analyzer, since the slope-decreasing region appears earlier in the analyzer located further upstream, the zero-point correction amount is calculated independently for each analyzer's output based on the measured values ​​sampled in their respective independent slope-decreasing regions.

[0069] Here, in order to indicate the tendency of blank data to change, Figure 4 The diagram shows the change over time of blank data for different crucibles MP, under the same waiting conditions as before, until the generation of the non-target gas stabilizes. Here, the data output by the CO detection unit 5 is presented as an example of blank data. Furthermore, the blank data output by the CO detection unit 5 is illustrated as an example in the coordinate graph used in the following description. Figure 4As shown, the switching valve V is switched so that the gas exported from the heating furnace 3 flows from the exhaust channel L3 to the analyzer AM. After a predetermined time (approximately 7 seconds in the coordinate diagram) elapses from the start of the blank measurement, the analyzer AM begins to detect elements. Furthermore, during the predetermined period from the start of element detection, a transitional state region is formed where the measured value continuously and monotonically increases. Additionally, if the transitional state region ends, a stable state region is formed where the measured value remains approximately constant. The stable state region can be defined, for example, as a region where the deviation from the moving average of the measured values ​​relative to the most recent predetermined number of points is below a predetermined value. In contrast, the transitional state region can be defined as a region outside the stable state region where the measured value changes by more than a predetermined value after a predetermined time elapsed following the switching of the valve V (after the start of the blank measurement step). Figure 4 As can be seen from the blank data, even though the absolute values ​​differ, each blank data point displays a waveform with a roughly similar shape, considered as a roughly single delayed response. That is, it can be seen that for each crucible MP, even if the amount of the non-target gas produced differs, the trend of change is similar. Furthermore, the blank data output from CO detector 5, CO2 detector 7, and H2O detector 8 show roughly the same waveform and the same trend. Additionally, although the waveform obtained from the blank data output from N2 detector 11 differs from the waveforms in other analyzers, a similar shape was obtained for each crucible MP. In the blank data output from CO2 detector 7, H2O detector 8, and N2 detector 11, each slope reduction region appears, for example, in a time period obtained by adding an independent delay time to the timing of the slope reduction region of CO detector 5 as a reference.

[0070] In this embodiment, such as Figure 4 As shown in the magnified section, the zero-point correction unit C2 sets the average value of the measurements from four consecutive points in the slope reduction region as the zero-point correction amount. Figure 5 The coordinate graph shows the results of setting the zero-point correction amount and performing zero-point correction on each blank data point. For example... Figure 5 As shown in the coordinate graph, regardless of the blank data, approximately the same waveform was obtained after zero-point correction, and the deviation was suppressed to below the predetermined value. That is, it can be seen that even if the measured values ​​are not sampled in the steady state region and the zero-point correction amount is set, zero-point correction can be performed with sufficient accuracy in elemental analysis based on multiple measured values ​​in the slope-reducing region, which is an earlier stage.

[0071] Next, the relationship between the sampling start time of the measured value used to set the zero-point correction amount in the transition state region and the zero-point correction accuracy will be explained. Figure 6The figure shows the original blank data and the zero-point correction results for the blank data with the sampling start point used to calculate the zero-point correction changed every second from 5 to 10 seconds. As can be seen from the figures, if the sampling start point (zero-point adjustment time) is changed, there is a tendency for the deviation to converge to approximately constant after a predetermined time. More specifically, according to... Figure 7 The relationship between the zero-point adjustment time and the standard deviation representing the deviation of the corrected blank data shows that if the adjustment occurs 7.5 seconds after the start of the analysis (after the current is applied to the crucible MP), the deviation becomes approximately constant. Furthermore, according to... Figure 8 As shown in the differential blank data obtained by time differentiation of the blank data, 7.5 seconds is the time when the differential blank data reaches its peak and the time when the slope decreases. That is, if a measured value is selected from the blank data and a zero-point correction is set in the time period of the region where the time derivative value tends to decrease in the transition state region, a zero-point correction can be performed to suppress the deviation to below a predetermined value.

[0072] In this embodiment, based on the above analysis results, the slope reduction region in the blank data output by the CO detection unit 5 located at the upstream end is defined as the region occurring within a time period of 7 seconds to 20 seconds from the start of heating of the crucible MP. Alternatively, the slope reduction region can also be defined as the region in the differential blank data obtained by time differentiation of the blank data, from the moment it reaches its peak to the moment it decreases to 10% of the peak value. Within this defined slope reduction region, the zero-point correction unit C2 samples the measured values ​​of multiple points from the blank data and sets an averaged zero-point correction amount, thereby achieving zero-point correction that suppresses the deviation to below a predetermined value. Furthermore, the timing (zero-point adjustment time) at which the zero-point correction unit C2 samples the measured values ​​used to calculate the zero-point correction amount can be manually set by the user at a predetermined time, or it can be automatically set as a trigger when the value becomes an extreme value in the differential blank data. More specifically, it can also be configured such that the control calculation mechanism further includes a receiving unit that receives the zero-point adjustment time set by the user, and the zero-point correction unit C2 samples the measured value used to calculate the zero-point correction amount based on the zero-point adjustment time received by the receiving unit. In this case, the zero-point correction unit C2 can also be configured as follows: as a reference, the time period of the slope reduction region in the blank data output by the CO2 detection unit 7, H2O detection unit 8, and N2 detection unit 11 is extracted, and an independent delay time is added to each of them to obtain the time period.

[0073] If the zero-point correction amount for blank data is set by the zero-point correction unit C2, the zero-point correction unit C2 stores the starting point of the sampling period for zero-point correction from the time of flow channel switching as the zero-point adjustment time, so that the same zero-point correction can be performed in the subsequent sample measurement step. In addition, the integral value of the blank data after zero-point correction is stored in the zero-point correction unit C2 as the correction amount of the element extracted from the crucible MP.

[0074] Next, if the sample determination step begins after changing the crucible MP and ending the dry firing, then as follows: Figure 4 As shown, a transitional region of rising measured values ​​appears in the raw data, similar to the blank measurement step. The zero-point correction unit C2 samples four points from the raw data at the same time as the sampling timing used to calculate the zero-point correction amount from the stored blank data, and calculates the zero-point correction amount for the raw data. Furthermore, Figure 2 The sample introduction timing control unit C4 introduces the sample into the crucible MP at a predetermined timing, initiating sample heating. This sample introduction timing simply requires a predetermined number of seconds elapsed since the zero-point adjustment time set by the zero-point correction unit C2. This number of seconds can be appropriately set considering factors such as the sample's flammability. From the viewpoint of accelerating elemental analysis, it is sufficient to introduce the sample at the end of the transitional state region or the beginning of the stable state region in the raw data. In this embodiment, as... Figure 3 As shown, the sample was put into operation immediately after the zero-point correction amount of the original data was set.

[0075] The measured values ​​of each element at various times after the sample is introduced are used as the raw data storage for each element. Figure 2 The sample gas measurement result storage unit C3 is shown. The zero-point correction unit C2 calculates the sample data obtained by zero-point correction using the corresponding zero-point correction amount for the original data of each element, and stores it in the sample data storage unit C5. Here, zero-point correction is performed sequentially whenever a new measurement value is obtained. Figure 2 The element quantity calculation unit C6, as shown, calculates the amounts of nitrogen, hydrogen, and oxygen contained in the sample before the extraction of sample gas based on the data of each sample. Specifically, the element quantity calculation unit C6 calculates the sum of the amounts of elements originating from the sample and the amounts of elements originating from the crucible MP based on the area value of the coordinate graph of the sample data, and calculates the amount of elements originating from the crucible MP based on the area value of the coordinate graph of the blank data obtained after zero-point correction using the zero-point correction amount. The element quantity calculation unit C6 calculates the amounts of elements contained in the sample sequentially based on the above-mentioned calculated amounts, and displays these values, for example, on a display screen.

[0076] Thus, the elemental analysis apparatus according to this embodiment, such as Figure 4As shown, since the zero-point correction is set based on multiple measurements within the decreasing slope region in the blank data, it eliminates the need for prolonged standby time, as was previously done, where the generation of the non-target gas was not allowed to proceed until the sample was introduced. This significantly reduces standby time. Furthermore, according to... Figures 6 to 8 The analysis results show that by using the slope to reduce the measured values ​​in the region, the deviation caused by zero-point correction can be suppressed to a small extent, and the same analytical accuracy as previous methods can be achieved.

[0077] Furthermore, since the number of sampling points used to calculate the zero-point correction is converged to four, even if the measurement value itself changes more than the change in noise in the slope region compared to the steady-state region, it is difficult to produce a deviation in the zero-point correction, and the influence of electrical noise can be reduced. That is, since the number of samples is even, the vibrations of electrical noise on the positive and negative sides can cancel each other out, thus suppressing the deviation in the zero-point correction.

[0078] Other implementation methods will be described.

[0079] In the described embodiment, the zero-point correction is calculated using only the measurements in the slope-decreasing region. However, depending on the allowable analytical precision, the zero-point correction can also be calculated by including measurements from regions other than the slope-decreasing region (e.g., the slope-increasing region) in the transition region.

[0080] The zero-point adjustment time used by the zero-point correction unit to calculate the zero-point correction amount does not necessarily have to be selected from the transition state region. For example, in cases where high-speed elemental analysis is desired, where the measured values ​​are sampled from the transition state region to calculate the zero-point correction amount and elemental analysis is performed under the same conditions as before, or where higher analytical accuracy is required, the zero-point correction unit can be configured to sample the measured values ​​from the stable state region of blank data to calculate the zero-point correction amount.

[0081] The number of sampling points used to calculate the zero-point correction is not limited to four points; it can also be one, two, or three points. Alternatively, the number of sampling points can be five or more.

[0082] The zero-point correction unit is not limited to performing zero-point correction whenever a new measurement value is obtained during the sample measurement process. For example, it can also perform zero-point correction on the entire set of original data after the entire measurement is completed.

[0083] The elements analyzed in an elemental analysis apparatus are not limited to nitrogen, hydrogen, and oxygen; for example, at least one of the three elements mentioned above can also be analyzed. Furthermore, elements other than nitrogen, hydrogen, and oxygen can also be analyzed.

[0084] The raw materials for crucibles are not limited to graphite; they can also be made from materials such as ceramics.

[0085] Furthermore, various modifications to the embodiments and combinations of parts of each embodiment are possible as long as they do not violate the spirit of the present invention.

[0086] Industrial applicability

[0087] According to the present invention, an elemental analysis apparatus can be provided that can significantly shorten the waiting time required for setting the zero-point correction amount, suppress the deviation of the zero-point correction amount, and improve the analysis accuracy compared to the past.

Claims

1. An elemental analysis method, comprising heating a sample placed in a crucible within a heating furnace, determining the amount of elements contained in a gas exiting the heating furnace by an analytical apparatus, and analyzing the elements contained in the sample, characterized in that the elemental analysis method includes: The blank determination step measures the amount of elements contained in the gas extracted from the furnace while only the crucible is heated; as well as The zero-point correction setting step involves setting the zero-point correction amount based on the measured values ​​in the transition region where the measured values ​​rise in the blank data obtained in the blank measurement step. The zero-point correction amount is set based on multiple measured values ​​in the slope-reducing region where the time derivative of the measured value in the transition state region becomes a decreasing trend.

2. The elemental analysis method according to claim 1, characterized in that, The region where the slope decreases is the region within a predetermined time period starting from the moment when the peak value is taken in the differential blank data obtained by time differentiation of the blank data.

3. The elemental analysis method according to claim 2, characterized in that, The analytical mechanism includes multiple analyzers, which are arranged sequentially from upstream to downstream on the outlet channel of the gas exiting the heating furnace. For each analyzer, the zero-point correction amount is set independently based on the slope reduction region that occurs at different times.

4. The elemental analysis method according to claim 2 or 3, characterized in that, The region of reduced slope that appears in the analyzer located on the upstream side of the analysis unit is the region that occurs in the time period of more than 7 seconds and less than 20 seconds from the start of the measurement of the blank data.

5. The elemental analysis method according to claim 4, characterized in that, The slope reduction region appearing in the analyzer located further downstream than the analyzer located at the upstream end is the region that appears after a predetermined delay time, using the slope reduction region appearing in the analyzer located at the upstream end as a reference.

6. The elemental analysis method according to any one of claims 1 to 3, characterized in that, The slope reduction region is the area from the moment when the slope becomes the peak in the differential blank data obtained by time differentiation of the blank data to the moment when it is reduced to 10% of the peak.

7. The elemental analysis method according to any one of claims 1 to 3, characterized in that, The zero-point correction is the average of the measured values ​​of four consecutive points in the slope reduction region of the blank data.

8. The elemental analysis method according to any one of claims 1 to 3, characterized in that, The elemental analysis method also includes: The sample determination procedure involves determining the amount of elements contained in the gas exiting the heating furnace while the crucible and the sample are heated; and The sample data generation step involves setting a zero-point correction amount based on the measured values ​​in the transitional region where the measured values ​​rise in the original data obtained in the sample measurement step, and calculating the sample data obtained by zero-point correction of the original data using the zero-point correction amount.

9. The elemental analysis method according to any one of claims 1 to 3, characterized in that, The elemental analysis method further includes a dry-firing step, in which only the crucible is heated, and the gas generated from the crucible is discharged into the exhaust channel instead of being introduced into the analysis mechanism. The blank determination step is initiated by switching the destination of the gas generated from the crucible from the exhaust channel to the analytical unit during or after the blank firing step.

10. An elemental analysis apparatus, comprising: Heating furnace, The sample placed in the crucible is heated; And an analytical apparatus to determine the amount of elements contained in the gas discharged from the heating furnace, wherein the elemental analysis device analyzes the elements contained in the sample. The elemental analysis apparatus is characterized by comprising: The blank measurement result storage unit stores the amount of elements contained in the gas exported from the heating furnace as measured by the analytical apparatus when only the crucible is heated, as blank data; as well as The zero-point correction unit sets the zero-point correction amount based on the measured values ​​in the transition region where the measured values ​​rise in the blank data. The zero-point correction amount is set based on multiple measured values ​​in the slope-reducing region where the time derivative of the measured value in the transition state region becomes a decreasing trend.

11. A storage medium, characterized in that, The apparatus contains a program for an elemental analysis device, the program being used in the elemental analysis device, which includes: a heating furnace for heating a sample placed in a crucible; and an analysis mechanism for determining the amount of elements contained in a gas exiting the heating furnace, the elemental analysis device analyzing the elements contained in the sample. The elemental analysis device uses a program to enable the computer to function as a blank measurement result storage unit and a zero-point correction unit. The blank measurement result storage unit stores the amount of elements contained in the gas discharged from the heating furnace as measured by the analytical apparatus when only the crucible is heated, as blank data. The zero-point correction unit sets the zero-point correction amount based on the measured values ​​in the transition region where the measured values ​​rise in the blank data. The zero-point correction amount is set based on multiple measured values ​​in the slope-reducing region where the time derivative of the measured value in the transition state region becomes a decreasing trend.

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