JP4575788B2 - Gas chromatograph apparatus and VOC measuring apparatus using the same - Google Patents

Description

  The present invention relates to a gas chromatograph apparatus and a VOC measurement apparatus using the same.

  Gas chromatographs are widely used for qualitative and quantitative analysis of components in gas, which introduces a gas to be measured together with a carrier gas into a gas separation column packed with a packing material, The contained gas components are separated by the retention time difference due to the interaction with the packing material in the gas separation column, and the separated gas components are derived from the gas separation column to be used as a thermal conductivity detector (TCD) or hydrogen flame. A chromatogram is obtained by detecting with a detector such as an ionization detector (FID) (see Patent Document 1).

In recent years, volatile organic compounds (VOCs) generated from paints and adhesives used in building interior materials and furniture have attracted attention as a causative agent for sick house syndrome and chemical sensitivity. The gas chromatograph apparatus described above is used for qualitative and quantitative measurement of VOCs.
Japanese Patent Application Laid-Open No. 2003-254956

  The gas chromatograph configured as described above detects the gas concentration of a plurality of types of gas components to be detected contained in the gas to be measured, but the detection output of the detector fluctuates with prolonged use. It is necessary to calibrate the output. In addition, since the amount of fluctuation in the detection output differs for each gas component to be measured, when calibrating the detection output, a plurality of sample gases for calibration mixed with a detection target gas component having a predetermined concentration using high-purity air as a carrier gas. It was necessary to prepare and calibrate the detection output for each gas component, which took time for calibration and required a long time for preparation for measurement.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas chromatograph apparatus that can easily perform a calibration operation and a VOC measurement apparatus that uses the gas chromatograph apparatus.

  In order to achieve the above object, the invention of claim 1 includes a gas separation column filled with a member that causes a flow delay in accordance with a gas component, and the inside of the gas separation column from the intake side of the gas separation column using air as a carrier gas. A gas supply port for supplying a gas to be measured that includes a plurality of types of detection target gas components in a carrier gas in the gas flow path. A semiconductor gas sensor which is provided on the exhaust side of the gas separation column and sequentially generates an output corresponding to the gas concentration of each detection target gas component, and the retention time of each detection target gas component and the peak of the output of the semiconductor gas sensor Storage means for storing calibration curve data in association with gas concentration data corresponding to the output peak, output peak and retention type of the semiconductor gas sensor Calculation means having a gas concentration detection function for obtaining the gas concentration of each detection target gas component based on the operation mode of the calculation means, detection mode for obtaining the gas concentration of each detection target gas component, or detection of the gas concentration Mode switching means for switching to one of calibration modes for calibrating the value, and calibration condition setting means for setting the gas type and gas concentration of the detection target gas component contained in the calibration gas supplied from the gas supply port in the calibration mode. When the operation mode is switched to the calibration mode, the calculation means is obtained from the output peak based on the gas type and gas concentration set by the calibration condition setting means and the output peak of the semiconductor gas sensor. Obtain a calibration formula to correct the output so that the gas concentration of the gas component to be detected matches the gas concentration set by the calibration condition setting means. In this case, for both the detection target gas component contained in the calibration gas and other detection target gas components, the peak of the output of the semiconductor gas sensor is corrected using the calibration calculation formula and stored in the storage means. The gas concentration corresponding to the corrected detection output is obtained from the calibration curve data.

  According to a second aspect of the present invention, in the first aspect of the present invention, the calculation means injects two kinds of calibration gases having different gas concentrations in the calibration mode to obtain the peak of the output of the semiconductor gas sensor at two gas concentrations. The value obtained by reading the output peak at the gas concentration of the calibration gas on the high concentration side from the calibration curve data is XOH, and the value obtained by reading the output peak at the gas concentration of the calibration gas on the low concentration side from the calibration curve data XOL, the result of measuring the peak of the output of the semiconductor gas sensor when the calibration gas on the high concentration side is injected is XH, and the result of measuring the peak of the output of the semiconductor gas sensor when the calibration gas on the low concentration side is injected is XL When the measured peak of the semiconductor gas sensor at the time of injection of the gas to be measured is X, and the value obtained by calibrating the output peak X is XC, the computing means is logXC And wherein the calibrating the peak of the output of the semiconductor gas sensor using (logXOH-logXOL) × (logX-logXL) / (logXH-logXL) + logXOL comprising calibration equation.

  According to a third aspect of the present invention, there is provided a LOG table in which the output peak of the semiconductor gas sensor and its logarithmic value are in a one-to-one correspondence, and the logarithmic value of the peak of the calibration curve data and each output A calibration curve table in which the gas concentration at each peak is associated with the one-to-one correspondence is registered in the storage means, LX is the logarithmic value of the output peak of the semiconductor gas sensor, LXC is the logarithmic value of the calibration value XC, LXOH, LXOL Are the logarithmic values of the outputs XOH and XOL, and LXH and LXL are the logarithmic values of the output peaks XH and XL at the time of the first and second calibration gas injection, respectively, and A = (LX0H−LX0L) / (LXH −LXY), B = (LX0L·LXH−LX0H · LXL) / (LXH−LXY), the computing means outputs the output of the semiconductor gas sensor in the detection mode. When the peak is read, this output peak is converted to a logarithmic value using the LOG table, the output peak is corrected using the calibration formula LXC = A × LLX + B, and then the corrected output is calculated from the calibration curve table. The gas concentration is obtained by reading the gas concentration corresponding to the peak.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, in the calibration mode, the calculation means is a known retention time of the gas type set by the calibration condition setting means and a calibration gas injection time point. The correction time, which is the time difference from the time until the peak of the output of the semiconductor gas sensor appears, is obtained, and in the detection mode, the time obtained by adding the correction time to the retention time of each detection target gas component from the time of injection of the gas to be measured It is characterized in that the output of the semiconductor gas sensor is taken in at the time when elapses.

  A fifth aspect of the present invention is a VOC measurement apparatus, characterized in that a qualitative quantitative measurement of a VOC component in the gas to be measured is performed using any one of the gas chromatograph apparatuses according to the first to fourth aspects.

  According to the first aspect of the present invention, the semiconductor gas sensor is used as the means for detecting the gas to be measured. In the semiconductor gas sensor, the output change caused by the change with time is generated at substantially the same rate with respect to all the detection target gas components. Therefore, if a calibration calculation formula is obtained from the output of the semiconductor gas sensor when a calibration gas is injected for any of the detection target gas components, another calibration target gas component can be obtained using this calibration calculation formula. Since the output when the gas is injected can be calibrated, it is not necessary to perform the calibration process for each detected gas component, and a gas chromatograph apparatus that can easily perform the calibration work can be realized.

  According to the second aspect of the present invention, a gas chromatograph apparatus can be realized in which the calibration work can be easily performed as in the first aspect of the present invention.

  According to the invention of claim 3, when the calculation means reads the output peak of the semiconductor gas sensor in the detection mode, the calculation means converts the output peak into a logarithmic value using the LOG table, and performs a calibration calculation of LXC = A × LLX + B. After correcting the output peak using the equation, the gas concentration is obtained by reading the gas concentration corresponding to the corrected output peak from the calibration curve table. The amount of processing can be reduced.

  According to the invention of claim 4, in the calibration mode, the known retention time of the gas type set by the calibration condition setting unit and the peak of the output of the semiconductor gas sensor from the time when the calibration gas is injected appear. In the detection mode, the output of the semiconductor gas sensor is output when the time obtained by adding the correction time to the retention time of each detection target gas component has elapsed in the detection mode. Since it is taken in, the gas concentration of each detection target gas component can be detected more accurately.

  According to the fifth aspect of the present invention, since the VOC measurement device is configured by using the gas chromatograph device of the first aspect, it is not necessary to perform the calibration process for each detected gas component, and the calibration work can be easily performed. A VOC measurement device can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present embodiment is a VOC measuring device using a gas chromatograph apparatus, and FIG. This VOC measuring device A includes a gas cylinder 20 filled with clean air containing no VOC at a predetermined pressure, a gas separation column 1 in which clean air is pumped as a carrier gas from a gas cylinder 20 through a gas flow path 21, and a gas cylinder. 20 and a check valve 22, a constant pressure valve 23, a flow rate adjustment valve 24 inserted between the gas flow path 21 to the intake side of the gas separation column 1, and provided for detecting a pressure change in the gas flow path 21. The semiconductor gas sensor is provided in the flow rate sensor 25, the gas supply port 26 provided on the intake side of the gas separation column 1 and supplied by injecting the gas to be measured into the carrier gas, and the exhaust port communicating with the atmosphere of the gas separation column 1 The detector 30 which consists of is provided.

  As shown in FIG. 3, the gas separation column 1 is configured such that a rubber heater 2 is closely disposed on the outer surface. The gas separation column 1 includes an outer cylinder 1a formed of a metal having high thermal conductivity such as stainless steel and copper, and an inner cylinder 1b made of, for example, Teflon (registered trademark) inserted in the outer cylinder 1a. It has a double cylinder structure, and the inner cylinder 1b is filled with a filler serving as a stationary phase. As this filler, an appropriate material according to the type of the detection target gas component or carrier gas in the gas to be measured is used. The rubber heater 2 is a flexible heater in which a resistor 3 is insulated with an insulating rubber such as a silicone rubber sheet. The resistor 3 spirals from one end side to the other end side on the outer peripheral surface of the gas separation column 1. The gas separation column 1 is arranged in close contact with the outer surface of the gas separation column 1. The gas separation column 1 is provided with a temperature sensor 4 made of a thermocouple. The thermocouple is insulated and coated with an insulating material such as a polyfluorinated ethylene resin (Teflon (registered trademark)) or glass wool. In this state, it is disposed on the outer surface of the gas separation column 1 and the temperature sensor 4 detects the temperature of the gas separation column 1.

  Next, the circuit configuration of the present embodiment will be described with reference to FIG. The gas chromatograph apparatus according to the present embodiment includes a power supply unit 31, a column heater control unit 32, a calculation processing unit 33 including a microcomputer, a display unit 34, and a flow rate measurement unit 35. The power supply unit 31 includes a power switch SW. When turned on, it has a function of generating the operating power supply voltage + V of each of the units 33 to 35.

  The column heater control unit 32 detects the temperature of the heater 2 that heats the gas separation column 1 with a temperature sensor 36 that is a thermistor, and the PID control unit 32a supplies power to the heater 2 through the phase control unit 32b based on the detected temperature. By controlling the above, the temperature of the gas separation column 1 is kept at a predetermined temperature set in advance.

  The arithmetic processing unit 33 takes in the detection output of the flow rate sensor 25 from the flow rate measurement unit 35, detects a flow rate change based on the detection output, and detects the injection timing of the gas to be measured from the gas supply port 26 by this detection. By controlling the energization of the heater 30a of the detector 30 consisting of a semiconductor gas sensor and the determination processing function, the temperature of the gas sensitive body of the detector 30 is divided into a high temperature period for heat cleaning and a low temperature period for taking in the detection output. A temperature control function that sets alternately, an analysis processing function that analyzes and quantitatively determines a gas component to be detected based on detection output and detection of injection timing taken in during a low temperature period, and a temperature sensor that detects the temperature of the gas separation column 1 The detection function when a calibration gas mixed with a detection target gas component having a predetermined concentration is injected from the gas supply port 26. It comprises a calibration function to calibrate the detection value and retention time of the gas concentration on the basis of the function of sending out the display data on the display unit 34.

  The display unit 34 is composed of a liquid crystal display and a controller, and is input in the analysis result and quantitative value of the detection target gas component obtained by the flow rate of the carrier gas, the analysis processing function, and the calibration mode based on the display data from the arithmetic processing unit 33. The set contents of the calibration conditions, the analysis result of the calibration gas, and the temperature of the gas separation column 1 are displayed.

  The flow rate sensor 25 is configured by using a wind speed sensor including a negative characteristic thermistor and a platinum coil. The flow rate sensor 25 is exposed to the gas flow path 21 and is heated by applying a voltage to the platinum coil. The temperature in the heated gas flow path 21 is detected by a negative characteristic thermistor. When a certain amount of carrier gas is flowing in the gas flow path 21, the temperature detected by the negative characteristic thermistor is a constant temperature. However, when the flow rate changes, that is, when the flow rate changes, the detection temperature changes, and when the flow rate stabilizes thereafter, the detected temperature is maintained at a constant temperature corresponding to the flow rate (flow rate). After A / D conversion, the data is taken into the arithmetic processing unit 33, and the arithmetic processing unit 33 monitors the flow rate of the carrier gas by converting the detected temperature into a flow rate.

  Thus, after the power switch SW is turned on and the gas chromatograph apparatus is operated, when the valve of the gas cylinder 20 is opened, clean air flows from the gas cylinder 20 as a carrier gas into the gas flow path 21, and the flow rate adjustment valve 24 The adjusted flow rate is pumped to the gas separation column 1. The flow rate of the carrier gas is constantly detected by the flow rate sensor 25 described above, and the arithmetic processing unit 33 monitors the flow rate of the carrier gas based on the detection output of the flow rate sensor 25.

  When the carrier gas is sent into the gas separation column 1 in this manner and a driving operation for supplying the gas to be measured including the detection target gas component from the gas supply port 26 is performed, the gas to be measured becomes the gas flow path 21. As a result, the flow velocity (flow rate) of the carrier gas flowing in the gas flow path 21 on the upstream side of the gas supply port 26 is instantaneously reduced.

  This instantaneous decrease instantaneously increases the temperature detected by the negative characteristic thermistor of the flow sensor 25. This instantaneous change in the detected temperature is detected by the arithmetic processing unit 33 by comparing the detection output of the flow sensor 25 with a preset reference level, and it is determined that the gas to be measured has been injected at the detected timing. Based on this timing, the retention time of the gas component detected by the detector 30 is measured.

  In this embodiment, a VOC measurement device is configured using a gas chromatograph device. For example, a qualitative quantitative measurement of VOC in the environment is performed by analyzing a gas component contained in indoor air. In this case, since the gas type of the detection target gas contained in the gas to be measured is determined (for example, toluene, ethylbenzene, metaxylene, orthoxylene, styrene, etc.), the detection output of the detector 30 for the detection target gas and the gas concentration Calibration curve data (see FIG. 4) indicating the converted value and the retention time are registered in advance in the memory 33a of the arithmetic processing unit 33.

  By the way, the detector 30 is composed of a semiconductor gas sensor, and the resistance value of the gas sensitive body changes according to the gas concentration of the gas component to be detected. The arithmetic processing unit 33 captures this resistance value change as a voltage change. . FIG. 4 shows calibration curve data when the gas concentration (ppb) is the vertical axis and the output change of the detector 30, that is, the value (bit) obtained by A / D conversion of the voltage change is the horizontal axis, Y = It is represented by aX ^ b. The calibration curve data in the figure shows the data for toluene.

  Therefore, the arithmetic processing unit 33 measures the time from the gas injection timing to the peak generation timing based on the detection output of the detector 30 that detects the gas component output from the gas separation column 1. The retention time of the gas component is measured, the retention time and the detected peak are collated with the data registered in the memory 33a to determine the detection target gas component, and detected from the peak value of the detection output at that time The concentration (quantitative value) of the gas component is determined, and the determination result is displayed on the display unit 34. The conversion of the gas concentration may be calculated from the area of the peak waveform regardless of the peak height of the detection output.

  FIGS. 10A and 10B show examples of chromatograms measured by the gas chromatograph apparatus of this embodiment. FIG. 10A is a chromatogram of a gas to be measured containing 1000 ppb of each of three types of detection target gas components (toluene, metaxylene, and styrene). The three peaks P1, P2, and P3 are toluene and metaxylene, respectively. Corresponds to styrene. FIG. 10 (b) is a chromatogram of a gas to be measured containing 1000 ppb of two kinds of detection target gas components (ethylbenzene and orthoxylene). The two peaks P4 and P5 correspond to ethylbenzene and orthoxylene, respectively. ing.

  As described above, the gas concentration of VCO such as toluene, ethylbenzene, metaxylene, orthoxylene, and styrene contained in the gas to be measured is measured. When starting the measurement, the gas corresponding to each detection target gas component is measured. Sensitivity needs to be calibrated. The gas sensitivity calibration method which is the gist of the present invention will be described below.

  Curves a and c shown by solid lines in FIGS. 10 (a) and 10 (b) show chromatograms measured at the beginning of use, and curves b and d shown by broken lines show chromatograms measured after 100 days. . The measurement results of each gas component obtained from these chromatograms are shown in Table 1 below. Here, as can be seen from FIGS. 10A and 10B and Table 1, the measurement results for each detection target gas component (the peak height (bit) of the detection output corresponding to each detection target gas component, and the detection output) The gas concentration (ppm) obtained from the peak of the above is about 1.2 times that in the initial stage of use after 100 days for any gas component. The output value increases at approximately the same rate.

  In the present embodiment using the semiconductor gas sensor for the detector 30 as described above, the variation in detection output that occurs according to long-term use occurs at substantially the same rate with respect to a plurality of detection target gas components. When the gas concentration obtained from the detection output of the detector 30 is calibrated, a calibration gas containing any one of the detection target gas components is supplied from the gas supply port 26, and the detection value at this time corresponds to the detection target gas component. If the correction coefficient is obtained, it is possible to correct detection values for other detection target gas components using the correction coefficient.

  Also, as shown in FIG. 4, when the calibration curve data is expressed with the logarithm of the peak height VS (bit) of the detection output on the horizontal axis and the logarithm of the gas concentration (ppb) on the vertical axis, the detection is performed within a certain interval of the gas concentration. The relationship between the output peak height and the gas concentration can be expressed by a linear function. A polygonal line L1 in FIG. 4 indicates calibration curve data of a concentration table registered in advance, and the relationship between the peak height of the detection output and the gas concentration is a gas concentration range (1: C1) and a range (C1: C2). Are each represented by a straight line. Here, the present embodiment uses a semiconductor gas sensor for the detector 30. When the detection output of the detector 30 fluctuates due to changes over time, the test data indicates that the detection output changes at the same rate in all gas concentration ranges. Therefore, it is considered that the polygonal line L1 indicating the calibration curve data at the initial stage of use moves in parallel with the polygonal line L2 due to the change over time. Therefore, when the detection output of the detector 30 is calibrated, a calibration gas containing a detection target gas component having a predetermined concentration Cx is injected, and the detection output X of the detector 30 at this time is obtained, and then the point (X , Cx), the detection output X may be corrected so that the polygonal line L2 passing through the polygonal line L1 overlaps.

  Here, in this embodiment, a calibration gas containing a target gas component (for example, toluene) having a predetermined concentration C4 in the high concentration side range (C1: C2) is injected, and the detection output XH of the detector 30 at this time is And a method of correcting the detection output using the detection output X0H at the initial use (one-point calibration) and a target gas component (for example, toluene) having a predetermined concentration C3 in the high concentration side range (C1: C2). The calibration gas and the calibration gas containing the target gas component having the predetermined concentration C4 in the low concentration side range (1: C1) are sequentially injected, and the detection output XH of the detector 30 when each calibration gas is injected. , XL and the detection outputs X0H, X0L at the time of initial use are calibrated using one of the methods for correcting the detection output (two-point calibration), and each correction method will be described below. Here, in calibrating the gas concentration obtained from the detection output of the detector 30, the operation mode of the arithmetic processing unit 33 is changed from the detection mode for obtaining the gas type and gas concentration of each detection target gas component to the detected value of the gas concentration. It is necessary to switch to the calibration mode for calibrating. That is, an operation input of a mode changeover switch (hereinafter referred to as a mode changeover switch) 37 that switches the operation mode to either the detection mode or the calibration mode is given to the arithmetic processing unit 33, and the operation processing unit 33 responds to the changeover operation of the mode changeover SW 37. Thus, the operation mode of the arithmetic processing unit 33 is switched to the calibration mode. The calibration mode includes a one-point calibration mode in which the output is calibrated using only one type of calibration gas, and a two-point calibration mode in which the output is calibrated using two calibration gases having different gas concentrations. Either the one-point calibration mode or the two-point calibration mode can be selected using the mode switching SW 37 described above. Note that the one-point calibration is based on the fact that the fluctuation in the detection output is small in the range where the gas concentration is relatively low, omitting the low concentration side calibration gas in the two-point calibration, and the detection output at this time is, for example, 100 ppb In this mode, only the high-concentration calibration gas in the two-point calibration is injected, and the output is calibrated with the detected output measured at this time and the 100 ppb toluene reference output. .

  First, the calibration operation when the mode switching SW 37 is used to switch to the two-point calibration mode will be described below. The inspector switches the operation mode of the arithmetic processing unit 33 to the calibration mode (two-point calibration mode) using the mode switching SW 37, and then uses the input unit 38 serving as calibration condition setting means for the first calibration gas. The gas type and gas concentration and the gas concentration of the second calibration gas (the gas type is the same as the first point) are set. When the calibration conditions are set by the input unit 38, the arithmetic processing unit 33 displays the first measurement (high concentration side) measurement start on the display unit 34 after a predetermined waiting time has elapsed, and from a speaker (not shown). A voice message such as “Measure the first point of the two-point calibration” or “Inject the first calibration gas” is output. At this time, when the person inspecting injects the first calibration gas from the gas supply port 26, the arithmetic processing unit 33 detects the injection timing of the calibration gas from the detection output of the flow sensor 25 in the same manner as described above. The detection output (peak height) XH of the detector 30 at the time when the retention time of the gas type set by the input unit 38 has elapsed from this injection timing is read. When the measurement process of the first calibration gas is completed, the arithmetic processing unit 33 displays the second point (low concentration side) measurement start on the display unit 34 after a predetermined waiting time has elapsed, and from the speaker. A voice message such as “Measure the second point of the two-point calibration” or “Inject the second calibration gas” is output. When the person inspecting injects the second calibration gas from the gas supply port 26, the arithmetic processing unit 33 detects the injection timing of the calibration gas from the detection output of the flow sensor 25 in the same manner as described above, The detection output (peak height) XL of the detector 30 at the time when the retention time of the gas type set by the input unit 38 has elapsed from this injection timing is read. Here, as the calibration gas, for example, two kinds of gases, that is, a gas containing 100 ppb of toluene and a gas containing 1000 ppb of toluene are used.

  When the measurement process is completed for the first and second calibration gases in this way, the arithmetic processing unit 33 determines the peak height of the detection output of the detector 30 at the two gas concentrations and the two gas points. Based on the peak height of the detection output at the initial use of the concentration (this value is referred to as a reference output), the following calibration calculation formula (1) used when calibrating the detection output is created.

  Here, X is a value obtained by normalizing the detection output (peak height) of the detector 30 with, for example, 0 to 1000, XC is a calibration value of the detection output X, and XOH is the gas concentration at the first point (high concentration side). A reference output, a value read from pre-registered calibration curve data, XOL is a reference output at the second (low concentration side) gas concentration, a value read from pre-registered calibration curve data, XH is The detection output of the detector 30 at the time of gas injection at the first point (high concentration side), XL is the detection output of the detector 30 at the time of gas injection at the second point (low concentration side). When the calibration calculation formula (1) is modified, the calibration calculation formula is expressed by the following formula (2).

  Here, the correction coefficients A and B are the reference outputs XOH and XOL at the gas concentrations at the two points read from the calibration curve data registered in advance, and the detection outputs of the detector 30 at the time of the first and second gas injections. XH and XL can be used for calculation, and the detection output can be calibrated using correction coefficients A and B obtained in advance in subsequent calculations. Thereafter, when the person in charge of the inspection switches the operation mode of the arithmetic processing unit 33 from the calibration mode to the detection mode using the mode switching SW 37, the arithmetic processing unit 33 outputs the detection output of the detector 30 in the above-described calibration calculation in the subsequent detection modes. Since correction is performed using Equation (2) and the gas concentration of the inspection target gas is calculated based on the corrected detection output and retention time, the change in detection output with time can be cancelled.

  In addition, when the arithmetic processing unit 33 performs the calibration processing using the above-described calibration calculation formula (3), logarithmic calculation is required, so that the calculation speed of the arithmetic processing unit 33 is reduced or the processing capacity of the arithmetic processing unit 33 is increased. It is necessary to use a high CPU. Therefore, a LOG table in which the detection output (peak height) of the detector 30 is normalized in a range of, for example, 0 to 1000 (normalized peak height) and the logarithmic value thereof in a one-to-one correspondence, The logarithm value of the value obtained by standardizing the detection output (peak height) of the registered calibration curve data and the calibration curve table in which the gas concentration at each detection output is correlated one to one are registered in the memory 33a. In this case, the arithmetic processing unit 33 can obtain the gas concentration by performing the calibration calculation without performing the logarithmic calculation using the LOG table and the calibration curve table registered in the memory 33a. The amount of calculation can be reduced.

  Here, LX is the logarithm of the detection output X of the detector 30, LXC is the logarithm of the calibration value XC, LXOH and LXOL are the logarithm of the reference outputs XOH and XOL, and LXH and LXL are the first and second points, respectively. Assuming that the logarithmic values of the detection outputs XH and XL at the time of injection of the calibration gas for the eye, the above calibration calculation formulas (1) and (2) are expressed by the following formulas (3) and (4).

  Thus, when the arithmetic processing unit 33 reads the detection outputs XH and XL of the detector 30 in the calibration mode, the arithmetic processing unit 33 converts the detection outputs XH and XL into logarithmic values LXH and LXL using the LOG table, and a calibration curve table. After reading the logarithmic values LX0H and LX0L of the reference output at the first and second gas concentrations from the above, the correction coefficients A and B are calculated using the above equations (5) and (6), and the logarithmic calculation Correction coefficients A and B can be obtained without performing. In the measurement mode, when the arithmetic processing unit 33 reads the detection output X of the detector 30, the detection output X is converted into a logarithmic value LX using a LOG table and calibrated using the above equation (4). The value LXC can be calculated, and by selecting the gas concentration of the detection output (logarithmic value) closest to the calibration value LXC from the calibration curve table, the gas concentration can be corrected by correcting the detection output X without performing logarithmic calculation. Can be requested.

  Next, the calibration operation when the mode switching SW 37 is used to switch to the one-point calibration mode will be described below. The inspector switches the operation mode of the arithmetic processing unit 33 to the calibration mode (one-point calibration mode) using the mode switching SW 37 and then uses the input unit 38 to select the gas type and gas concentration of the high-concentration gas. Set. In the arithmetic processing unit 33, when the calibration condition is set by the input unit 38, the measurement start is displayed on the display unit 34 after a predetermined waiting time has elapsed, and “inject calibration gas” from a speaker (not shown). The voice message is output. At this time, when the person in charge of the inspection injects the high-concentration calibration gas from the gas supply port 26, the arithmetic processing unit 33 detects the injection timing of the calibration gas from the detection output of the flow sensor 25 in the same manner as described above. The detection output XH of the detector 30 at the time when the retention time of the gas type set by the input unit 38 has elapsed from this injection timing is read. When the measurement of the detection output VH is completed, the arithmetic processing unit 33 detects the detection output VH measured by injecting the calibration gas and the detection output XL (that is, the calibration curve data of toluene) read from the calibration curve data registered in advance. From the detection output at a concentration of 100 ppb to 100 ppb) and the detection output at the initial stage of use at the above two gas concentrations (this output is referred to as a reference output). Thus, the above calibration calculation formulas (1) and (2) are created, and the detection output of the detector 30 is corrected using the calibration calculation formulas (1) and (2) in the subsequent detection modes.

  Similarly to the case of two-point calibration, the value (normalized peak height) obtained by normalizing the detection output (peak height) of the detector 30 within a range of 0 to 1000, for example, and the logarithmic value thereof are 1: 1. Corresponding LOG table, logarithmic value of a standardized detection output (peak height) of calibration curve data registered, and a calibration curve table in which the gas concentration in each detection output is correlated on a one-to-one basis Are registered in the memory 33a (not shown), the arithmetic processing unit 33 uses the LOG table and the calibration curve table registered in the memory 33a to perform a calibration calculation without performing a logarithmic calculation, thereby calculating the gas concentration. And the calculation amount of the arithmetic processing unit 33 can be reduced.

  That is, when the arithmetic processing unit 33 reads the detection output XH of the detector 30 in the calibration mode, it reads the detection output XH and the detection output XL (detection output at a concentration of 100 ppb from the calibration curve data of toluene using the LOG table. The logarithmic values LXH and LXL are converted into logarithmic values LXH and LXL, and the logarithmic values LX0H and LX0L of the reference outputs at the first and second gas concentrations are read from the calibration curve table, and then used in the two-point calibration. By calculating the correction coefficients A and B using the equations (5) and (6), the correction coefficients A and B can be obtained without performing logarithmic calculation. In the measurement mode, when the arithmetic processing unit 33 reads the detection output X of the detector 30, the detection output X is converted into a logarithmic value LX using a LOG table and calibrated using the above equation (4). The value LXC can be calculated, and by selecting the gas concentration of the detection output (logarithmic value) closest to the calibration value LXC from the calibration curve table, the gas concentration can be corrected by correcting the detection output X without performing logarithmic calculation. Can be requested.

  In this embodiment, only the gas concentration is calibrated. However, in the calibration mode, the arithmetic processing unit 33 detects the retention time (known) of the gas type set by the input unit 38 and the detector 30 from the time when the calibration gas is injected. The time difference until the peak of the detection target gas component contained in the calibration gas appears in the output of the calibration gas (this time difference is referred to as the correction time dT). By capturing the peak of the output of the semiconductor gas sensor when the time obtained by adding the correction time dT to the retention time of the gas component has elapsed, the gas concentration of each detection target gas component can be measured more accurately.

  In addition, the calibration gas used for calibration has a long-term stability of the gas concentration compared to the detection target gas component such as toluene, and a reference gas (for example, octane) that generates a peak within the retention time of the detection target gas component. May be mixed together with the gas component to be detected. In the calibration mode, the arithmetic processing unit 33 obtains the gas concentration of the reference gas from the peak of the output of the detector 30, and calculates the gas concentration and a predetermined threshold level. It is possible to determine whether the calibration gas is normal or not by comparing the heights of the two. That is, the arithmetic processing unit 33 determines that the calibration gas has deteriorated when the gas concentration of the reference gas falls below the threshold level, and displays the abnormality of the calibration gas on the display unit 34. It is possible to prevent erroneous calibration using the deteriorated calibration gas.

  In this embodiment, the VOC measurement device using the gas chromatograph device has been described. However, the purpose of the gas chromatograph device is not limited to the measurement of VOC. For example, the gas component contained in the exhaled gas is used. Of course, the measurement can be used for a breath component analyzer for finding a disease and confirming a therapeutic effect, and is not limited to the use.

It is a circuit block diagram of one Embodiment of this invention. It is a flow-path block diagram same as the above. It is a perspective view of the gas separation column used for the same as the above. It is explanatory drawing of the calibration curve used for the same as the above. (A) (b) is explanatory drawing of the chromatogram measured using the same as the above.

Explanation of symbols

30 detector 33 arithmetic processing unit 33a memory 38 input unit

Claims (5)

A gas separation column packed with a member that causes a flow delay according to the gas component;
A pumping means for pumping air as a carrier gas from the intake side of the gas separation column into the gas separation column via a gas flow path;
A gas supply port which is provided in the middle of the gas flow path and supplies a measurement gas containing a plurality of types of detection target gas components in the carrier gas in the gas flow path;
A semiconductor gas sensor which is provided on the exhaust side of the gas separation column and sequentially generates an output corresponding to the gas concentration of each detection target gas component;
Storage means for storing calibration curve data in which the retention time of each detection target gas component and the peak of the output of the semiconductor gas sensor are associated with the gas concentration data corresponding to the peak of the output;
Arithmetic means having a gas concentration detection function for obtaining the gas concentration of each detection target gas component based on the peak of output of the semiconductor gas sensor and the retention time;
Mode switching means for switching the operation mode of the computing means to either a detection mode for obtaining the gas concentration of each detection target gas component or a calibration mode for calibrating the detection value of the gas concentration;
Calibration condition setting means for setting the gas type and gas concentration of the detection target gas component contained in the calibration gas supplied from the gas supply port in the calibration mode,
When the operation mode is switched to the calibration mode, the calculation means starts from the output peak based on the gas type and gas concentration set by the calibration condition setting means and the output peak of the semiconductor gas sensor. A calibration calculation formula for correcting the output so that the obtained gas concentration of the gas component to be detected matches the gas concentration set by the calibration condition setting means is obtained, and the detection contained in the calibration gas in the detection mode For both the target gas component and other detection target gas components, the peak of the output of the semiconductor gas sensor is corrected using the calibration calculation formula, and the corrected detection is performed from the calibration curve data stored in the storage means. A gas chromatograph apparatus for obtaining a gas concentration corresponding to an output.   The calculation means injects two kinds of calibration gases having different gas concentrations in the calibration mode to obtain the peak of the output of the semiconductor gas sensor at the two gas concentrations, and uses the calibration curve data for calibration on the high concentration side. The value obtained by reading the output peak at the gas concentration of the gas is XOH, the value obtained by reading the output peak at the gas concentration of the calibration gas on the low concentration side from the calibration curve data is XOL, and the calibration gas on the high concentration side is injected. XH is the result of measuring the peak of the output of the semiconductor gas sensor at the time, XL is the result of measuring the peak of the output of the semiconductor gas sensor when the calibration gas on the low concentration side is injected, and the output of the semiconductor gas sensor at the time of injecting the measurement gas When the peak of X is X and the value obtained by calibrating the output peak X is XC, the calculation means is logXC = (logXOH−logXOL) × (logX−lo 2. The gas chromatograph according to claim 1, wherein the peak of the output of the semiconductor gas sensor is calibrated using a calibration calculation formula of (gXL) / (logXH-logXL) + logXOL.   A LOG table in which the output peak of the semiconductor gas sensor is associated with the logarithmic value thereof in a one-to-one correspondence, and the logarithmic value of the output peak of the calibration curve data and the gas concentration in each output peak are in a one-to-one correspondence. The calibration curve table is registered in the storage means, LX is the logarithmic value of the output peak of the semiconductor gas sensor, LXC is the logarithmic value of the calibration value XC, LXOH and LXOL are the logarithmic values of the outputs XOH and XOL, LXH, Let LXL be the logarithmic values of the output peaks XH and XL at the time of the first and second calibration gas injection, respectively, A = (LX0H−LX0L) / (LXH−LXY), B = (LX0L·LXH−LX0H) When LXL) / (LXH-LXY), the calculation means reads the peak of the output of the semiconductor gas sensor in the detection mode. The log is converted into a logarithmic value using the LOG table, the output peak is corrected using the calibration formula LXC = A × LLX + B, and the gas concentration corresponding to the corrected output peak is calculated from the calibration curve table. The gas chromatograph according to claim 2, wherein the gas concentration is obtained by reading.   In the calibration mode, the arithmetic means is a time difference between the known retention time of the gas type set by the calibration condition setting means and the time from when the calibration gas is injected until the output peak of the semiconductor gas sensor appears. A certain correction time is obtained, and in the detection mode, the output of the semiconductor gas sensor is captured when a time obtained by adding the correction time to the retention time of each detection target gas component has elapsed since the injection of the gas to be measured. The gas chromatograph apparatus according to any one of claims 1 to 3. 5. A VOC measurement apparatus that performs qualitative quantitative measurement of a VOC component in the gas to be measured using the gas chromatograph apparatus according to any one of claims 1 to 4.

Images