JP5369856B2 - Measuring method - Google Patents

Description

  The present invention relates to a measurement method for calculating the concentration of ethanol and the concentration of methanol contained in denatured ethanol for fuel.

  As part of global warming countermeasures, interest in reducing carbon dioxide emissions has increased, and ethanol for fuel (EtOH) has attracted attention as an alternative fuel for gasoline. In the US, as a measure for preventing the use of such fuel ethanol for other purposes, addition of a modifier such as gasoline (a mixture of several hydrocarbons) is obligatory. The quality standard of ethanol for fuel to which a modifier is added (hereinafter also referred to as “modified ethanol for fuel”) is defined by the American Society for Testing and Materials (ASTM). ASTM D5501 describes modified ethanol for fuel. The concentration of ethanol (92.1% by volume or more) and the concentration of methanol (MeOH) (0.5% by volume or less) are to be confirmed. The quality required for fuel-modified ethanol is defined by ASTM D4806.

In order to calculate the concentration of ethanol and the concentration of methanol in such denatured ethanol for fuel, a gas chromatograph is used (for example, see Patent Document 1).
Here, an example of a gas chromatograph capable of calculating the concentration of ethanol, the concentration of methanol, and the concentration of modifier in the denatured ethanol for fuel will be described. FIG. 7 is a schematic configuration diagram of an example of a conventional gas chromatograph. In the gas chromatograph 51, a sample vaporizing chamber 52 into which a sample (modified ethanol for fuel) is introduced and vaporized, a column 55 to which the sample vaporizing chamber 52 and the inlet end are connected, and hydrogen to be connected to the outlet end of the column 55 are connected. A flame ionization detector (FID) 53, a temperature control device 56 for controlling the temperature of the column 55, and a computer (control unit) 60 are provided.

  The column 55 is tubular, its inner diameter is 0.25 mm, and its length is 100 m to 150 m. And the stationary phase is apply | coated inside the column 55, and when sample gas passes the inside of the column 55, the speed according to the distribution coefficient or solubility of each compound (ethanol, methanol, hydrocarbon) As each compound moves, the compounds are sequentially discharged from the outlet end.

The computer 60 creates a chromatogram of time t versus ion intensity I based on the ion intensity signal (detection signal) sequentially detected by the FID 53, so that the ethanol peak area value AE is obtained by the corrected area percentage method. And the methanol peak area value AM, the ethanol concentration and the methanol concentration in the fuel-modified ethanol are calculated.
FIG. 8 is an example of a chromatogram created using a column having a length of 150 m. The injection amount of denatured ethanol for fuel is 0.5 μL, the flow rate of He gas is 24 cm / second, and the column temperature is set to 60 ° C. (15 minutes) -30 ° C./minute-250° C. (23 minutes). Controlled. As shown in FIG. 8, there is a peak indicating ethanol at the position of time t = 14 minutes, a peak indicating methanol at the position of time t = 13 minutes, and time t = 38 until all compounds are detected. It has become minutes.
FIG. 9 is an example of a chromatogram created using a column having a length of 100 m. The injection amount of denatured ethanol for fuel is 0.5 μL, the flow rate of He gas is 24 cm / second, and the column temperature is set to 15 ° C. (12 minutes) −30 ° C./minute−250° C. (19 minutes). Controlled. As shown in FIG. 9, there is a peak indicating ethanol at the position of time t = 10 minutes, a peak indicating methanol at the position of time t = 8 minutes, and time t = 29 until all compounds are detected. It has become minutes.
In addition, the vertical axis in the chromatograms shown in FIGS. 8 and 9 indicates the ionic strength I, and the horizontal axis indicates the time t.

  On the other hand, a gas chromatograph including a first column and a second column, so-called multi-dimensional GC is known (for example, see Patent Document 2). An analysis example of environmental pollutants has been reported using this multi-dimensional GC (eg, see Non-Patent Document 1).

JP 2008-190942 A JP 2006-226678 A

Abstracts of the 16th Environmental Chemistry Conference P644-645 “Measurement of Environmental Pollutants by MDGCMS”

By the way, in order to quantify the concentration of ethanol and the concentration of methanol in fuel-modified ethanol, ethanol, methanol, and hydrocarbons added as a modifier are not co-eluted from the outlet end of the column 55. It is necessary to increase the length of the column 55 to 100 m or 150 m. However, when the length of the column 55 is 100 m or more, as described above, the measurement time until all the compounds are detected becomes as long as 29 to 38 minutes.
Further, when a column having a length of 150 m is used, in order to prevent co-elution of ethanol, methanol, and hydrocarbons from the outlet end of the column 55, the temperature of the column 55 is set to 60 ° C. (15 Min) −30 ° C./min −250 ° C. (23 min) is sufficient, but when using a column having a length of 100 m, the temperature controller 56 controls the temperature of the column 55 to 15 ° C. (12 min). ) −30 ° C./min −250 ° C. (19 minutes), that is, the temperature controller 56 needs to be equipped with a low-temperature addition device, which is costly.
Therefore, the present invention uses a multidimensional gas chromatograph for calculating the concentration of ethanol and the concentration of methanol contained in the denatured ethanol for fuel in a short measurement time without requiring a low-temperature addition device or the like. An object is to provide a measurement method.

The measurement method of the present invention, which has been made to solve the above problems, separates the sample into each component fraction by introducing the sample from the inlet end, and sequentially discharges the component fraction from the outlet end. A first column, a second column for separating the component fraction into each compound by introducing the component fraction into the interior from the inlet end, and sequentially discharging the compound from the outlet end; and a first detector A second detector connected to the outlet end of the second column, a flow path changing connection mechanism to which the outlet end of the first column, the inlet end of the second column, and the first detector are connected. A measurement method for calculating the concentration of each compound contained in the sample using a gas chromatograph, wherein the sample is a mixture of a compound group having polarity and a compound group having no polarity. A denatured ethanol for fuel. A non-polar liquid phase is applied to the inside of the second column, and a polar liquid phase is applied to the inside of the second column. The flow path changing connection mechanism is connected to the first column. Switchable so that either the outlet end and the inlet end of the second column are connected to flow, or the outlet end of the first column and the first detector are connected to flow. And between the setting start time and the setting end time, from the flow passage flowing through the outlet end of the first column and the first detector, the outlet end of the first column and the second column A flow path changing step for controlling the flow path changing connection mechanism so as to be a flow path that flows through the inlet end of the first inlet, and a detection signal detected by the first detector and the second detector. The concentration of ethanol and methanol contained in the modified ethanol for fuel Look including a calculation step of calculating the concentration of Le, said in the calculation step, the a first peak area value of the first detector detected modifier, the second detector detected modifier peak area value And, based on the sensitivity difference between the first detector and the second detector, calculate the peak area value in the second detector of the total modifier contained in the fuel-modified ethanol, and Ethanol contained in the denatured ethanol for fuel based on the peak area value of ethanol and the peak area value of methanol in the second detector based on the peak area value in the second detector of the total modifier The concentration of methanol and the concentration of methanol are calculated .

According to the measurement method of the present invention, since the sample is denatured ethanol for fuel, the sample is a mixture of a compound group having polarity and a compound group having no polarity. Therefore, in the multi-dimensional GC, a nonpolar liquid phase is applied to the inside of the first column, and a polar liquid phase is applied to the inside of the second column.
Thereby, for example, the flow path changing connection mechanism first connects the outlet end of the first column and the first detector. Thereby, the compound group (ethanol and methanol) having polarity and the compound group having no polarity are separated in the first column.
When the set start time is reached, the flow path connecting the outlet end of the first column and the first detector becomes the flow path connecting the outlet end of the first column and the inlet end of the second column. change. Thereby, since the compound groups having polarity in the first column are not separated from each other, the compound groups having a polarity (component fraction) are introduced into the second column and moved while moving through the second column. To be separated into compounds.

When the set end time is reached, the flow path connecting the outlet end of the first column and the inlet end of the second column becomes the flow path connecting the outlet end of the first column and the first detector. change. Thereby, when all the compound groups having polarity are introduced into the second column, the remaining compound groups having no polarity are not introduced into the second column. That is, the remaining group of compounds having no polarity passes through only the length of the first column and reaches the first detector in a short measurement time.
Based on the detection signals detected by the first detector and the second detector in this way, the concentration of ethanol and the concentration of methanol contained in the fuel-modified ethanol are calculated.

  As described above, according to the measurement method of the present invention, the denatured ethanol for fuel is a mixture of a group of compounds having polarity and a group of compounds having no polarity. By applying a liquid phase and applying a polar liquid phase to the inside of the second column, high decomposition performance can be achieved. As a result, a low temperature addition device or the like is not required, and fuel can be used in a short measurement time. The concentration of ethanol and the concentration of methanol contained in the denatured ethanol can be calculated.

(Means and effects for solving other problems)
In the above invention, the first column may be coated with 100% dimethylpolysiloxane, and the second column may be coated with a polyethylene glycol liquid phase. Good.
In addition, the measurement method of the present invention includes a first column that separates the sample into each component fraction by introducing the sample from the inlet end, and sequentially discharges the component fraction from the outlet end; The component fraction is introduced into the interior, whereby the component fraction is separated into each compound, and the second column for sequentially discharging the compound from the outlet end, the first detector, and the second column Using a gas chromatograph comprising a second detector connected to the outlet end, and a flow path changing connection mechanism connecting the outlet end of the first column, the inlet end of the second column, and the first detector. A measurement method for calculating the concentration of each compound contained in the sample, wherein the sample is a denatured ethanol for fuel that is a mixture of a compound group having polarity and a compound group having no polarity. The first column contains a nonpolar liquid. In addition, a polar liquid phase is applied to the inside of the second column, and the flow path changing connection mechanism connects the outlet end of the first column and the inlet end of the second column. It can be switched so that it is connected so that it flows or the outlet end of the first column and the first detector are connected so as to flow, setting start time and setting end Between the time, the flow path flowing through the outlet end of the first column and the first detector, the flow path flowing through the outlet end of the first column and the inlet end of the second column, So as to be contained in the fuel-modified ethanol based on the flow path changing step for controlling the flow path changing connection mechanism and the detection signals detected by the first detector and the second detector. Calculator to calculate the concentration of ethanol and methanol And the difference in sensitivity between the first detector and the second detector to calculate the concentration of ethanol and the concentration of methanol contained in the denatured ethanol for fuel in the calculation step, in the second detector A sensitivity correction coefficient indicating the relationship between the ethanol concentration and the peak area value, and a setting step for setting a sensitivity correction coefficient indicating the relationship between the methanol concentration and the peak area value in the second detector .

It is a schematic structure figure of an example of the gas chromatograph concerning an embodiment. It is a schematic block diagram of an example of the connection mechanism for flow-path change shown in FIG. It is an example of a chromatogram. It is an example of a chromatogram. It is a flowchart for demonstrating an example of the setting method by a setting part. It is a flowchart for demonstrating an example of the setting method by a setting part. It is a flowchart for demonstrating an example of MDGC method. It is a schematic block diagram of an example of the conventional gas chromatograph. It is an example of the chromatogram created using the column which is 150 m in length. It is an example of the chromatogram created using the column which is 100 m in length.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and it goes without saying that various aspects are included without departing from the spirit of the present invention.

FIG. 1 is a schematic configuration diagram of an example of a gas chromatograph that analyzes ethanol and methanol in fuel-modified ethanol according to an embodiment. 2 is a schematic configuration diagram of an example of the flow path changing connection mechanism shown in FIG.
The gas chromatograph 1 includes a sample vaporizing chamber 2 into which a sample (modified ethanol for fuel) is introduced and vaporized, a first column 5 to which an inlet end is connected, a first hydrogen flame ionization detector (first FID) 3, , The second column 6, the second flame ionization detector (second FID) 7 connected to the outlet end of the second column 6, the outlet end of the first column 5, the inlet end of the second column 6, A flow path changing connection mechanism 40 to which one FID 3 is connected, temperature control devices 9a and 9b for controlling the temperatures of the first column 5 and the second column 6, and a computer (control unit) for controlling the entire gas chromatograph 1 10. The first column 5 and the second column 6 are accommodated in a column oven (not shown), and the column oven is controlled by the temperature control devices 9a and 9b according to a predetermined temperature program during sample analysis. As a temperature program, at least the measurement target components methanol and ethanol in the denatured ethanol for fuel from the start of analysis are maintained at a temperature of 35 ° C. to 40 ° C. during the time when they are discharged from the first column 5, It is preferable to increase the temperature up to the vicinity of the heat-resistant temperature of one column 5 with an appropriate heating rate. By setting it as such a temperature program, the compound (ethanol and methanol) which has polarity in the 1st column 5 in low temperature conditions, such as 35 to 40 degreeC, and a compound with low polarity and a low boiling point (for example, a certain hydrocarbon group) ), And discharged from the first column 5 and introduced into the second column 6, and then the remaining compound group can be discharged from the first column 5 earlier to shorten the measurement time.
In the following examples, the temperature was set to reach 230 ° C. at a rate of temperature increase of 20 ° C./min after holding at 35 ° C. for 2.5 minutes.

The first column 5 is tubular and has an inner diameter of 0.25 mm and a length of 30 m. The first column 5 is coated with 100% dimethylpolysiloxane as a stationary phase, and when the sample gas passes through the first column 5, the rate according to the distribution coefficient or solubility of each compound. Each compound moves and the compounds are discharged sequentially from the outlet end. That is, since the stationary phase applied to the inside of the first column 5 has no polarity, the polar compound group (ethanol, methanol) moves through the first column 5 at a high speed, so On the other hand, a group of compounds having no polarity (a plurality of types of hydrocarbon groups) that are not separated into compounds are separated into the respective compounds according to boiling points while moving through the first column 5 at a slow speed. . At this time, in the measurement of the denatured ethanol for fuel, it is only necessary to be able to calculate the concentration of ethanol and the concentration of methanol. Therefore, several types of hydrocarbon groups do not have to be separated from each other.
Examples of the first column coated with 100% dimethylpolysiloxane as a stationary phase include “Rtx-1 (manufactured by Restex)”.

The second column 6 is tubular and has an inner diameter of 0.32 mm and a length of 30 m. The second column 6 is coated with polyethylene glycol as a stationary phase. When the sample gas passes through the second column 6, each compound has a rate corresponding to the distribution coefficient or solubility of each compound. Is moving, and the compounds are discharged sequentially from the outlet end. That is, since the stationary phase applied to the inside of the second column 6 has polarity, the compound group (ethanol, methanol) having polarity is separated into each compound while moving through the second column 6. It will be.
Examples of the second column coated with polyethylene glycol as the stationary phase include “Rtx-WAX (manufactured by Restex)”.

The flow path changing connection mechanism 40 includes a switching element (connector) 41, a pressure control device (APC) 42 that supplies a carrier gas (He gas) at a set pressure P, and a three-way solenoid valve 43.
The switching element 41 includes a first column introducing portion 41a that is a space in which the outlet end of the first column 5 is inserted from the right side, and a second column introducing portion that is a space in which the inlet end of the second column 6 is inserted from the left side. 41b and a connection channel 41c that connects the first column introduction part 41a and the second column introduction part 41b at the center.
Further, a flow path connected to the first FID 3 is formed on the left side of the first column introduction part 41a, and a He gas pressure ΔP1 is lowered at the center of the first column introduction part 41a. A flow path connected to the APC 42 through the one resistance tube 41d is formed. As a result, the pressure in the first column introduction portion 41a is always a constant pressure P-ΔP1.

  Further, the second column introduction part 41b is connected to the APC 42 through the second resistance pipe 41e for lowering the pressure ΔP2 (> ΔP1) of He gas at the center part (see FIG. 2B) or A flow path that can be switched by the three-way solenoid valve 43 is formed so as to be connected to the APC 42 without passing through the second resistance tube 41e (see FIG. 2A). Thereby, when it connects with APC42 via the 2nd resistance pipe | tube 41e, the pressure of the 2nd column introducing | transducing part 41b will be P- (DELTA) P2, As a result, the 1st column introducing | transducing part 41a is P- (DELTA) P1. Accordingly, the outlet end of the first column 5 and the inlet end of the second column 6 are circulated. On the other hand, when connected to the APC 42 without passing through the second resistance tube 41e, the pressure of the second column introduction part 41b is P, and as a result, the pressure of the first column introduction part 41a is P-ΔP1. The outlet end of the first column 5 and the first FID 3 are circulated.

The computer 10 includes a CPU (control unit) 11, and further includes a memory (storage unit) 12, a keyboard and mouse that are input devices (not shown), and a display device (not shown) having a monitor screen and the like. It is connected.
The function processed by the CPU 11 will be described as a block. The connection mechanism control unit 21 that controls the three-way electromagnetic valve 43 of the flow path changing connection mechanism 40, the first detector control unit 22 that controls the first FID 3, A second detector control unit 23 for controlling the second FID 7, a measurement unit 24 for calculating the concentration of ethanol and the concentration of methanol in the denatured ethanol for fuel, and the sensitivity difference F1 and sensitivity between the first FID 3 and the second FID 7 And a setting unit 25 for setting correction coefficients αE, αM and the like. Details of the sensitivity difference F1 and the sensitivity correction coefficients αE and αM will be described later. The memory 12 includes a set time storage area 12a for storing a set start time Ts and a set end time Te (for example, Ts = 1.42 minutes, Te = 1.96 minutes), a sensitivity difference F1 and a sensitivity correction coefficient αE. , ΑM, and a setting condition storage area 12b.

The connection mechanism control unit 21 controls the three-way electromagnetic valve 43 of the flow path changing connection mechanism 40 based on the set times Ts and Te stored in the set time storage area 12a or an operation signal from the input device. When calculating the concentration of each compound contained in the denatured ethanol for fuel, first, the APC 42 is connected to the second column introduction part 41b without the second resistance tube 41e. It connects so that an exit end and 1st FID3 may distribute | circulate.
Next, when the set start time Ts (for example, Ts = 1.42 minutes) is reached, the APC 42 is connected to the second column introduction part 41b via the second resistance tube 41e, thereby It connects so that it may distribute | circulate with the inlet end of the 2nd column 6. FIG.
When the set end time Te (for example, Te = 1.96 minutes) is reached, the APC 42 is connected to the second column introduction portion 41b without the second resistance tube 41e, so that the outlet end of the first column 5 It connects so that one FID3 may distribute | circulate.
The setting start time Ts and the setting end time Te (for example, Ts = 1.42 minutes, Te = 1.96 minutes) are stored in the setting time storage area 12a in advance, but ethanol and methanol are the first. This is determined by confirming in advance the time discharged from the outlet end of the column 5 (see FIG. 3B). That is, FIG. 3B shows that the fuel-modified ethanol is used under the same conditions as the actual sample measurement conditions (carrier gas linear velocity, It is a chromatogram obtained by analyzing in advance with a column oven temperature program or the like. From this, it can be seen that the retention time of methanol and ethanol is approximately 1.47 minutes to 1.91 minutes. From this analysis result, under the same analysis conditions, the setting start time Ts can be set to 1.42 minutes, for example, and the setting end time Te can be set to, for example, Te = 1.96 minutes.

The first detector control unit 22 performs control to create a chromatogram having time t versus ion intensity I based on the ion intensity signal detected by the first FID 3. For example, FIG. 3A is an example of a chromatogram created when calculating the concentration of each compound contained in denatured ethanol for fuel. Since the length of the first column 5 is 30 m, the time until all compounds are detected is t = 9 minutes.
The second detector control unit 23 performs control to create a chromatogram with time t versus ion intensity I based on the ion intensity signal detected by the second FID 7. For example, FIG. 4 is an example of a chromatogram created when calculating the concentration of each compound contained in denatured ethanol for fuel. There is a peak indicating ethanol at a position at time t = 4 minutes, a peak indicating methanol at a position at time t = 3.5 minutes, and a time t = 4 minutes until all compounds are detected. .

The setting unit 25 performs control to set the sensitivity difference F1 between the first FID3 and the second FID7, sensitivity correction coefficients αE, αM, and the like. In the gas chromatograph 1, since the sample is measured based on the ion intensity signals (detection signals) detected by the first FID3 and the second FID7, before the sample is measured by the measuring unit 24, The sensitivity difference F1 between the first FID3 and the second FID7, sensitivity correction coefficients αE, αM, and the like are set using the two standard samples and the third standard sample.
Here, a setting method (setting process) in which the setting unit 25 sets the sensitivity difference F1 between the first FID3 and the second FID7 and the sensitivity correction coefficients αE and αM will be described. 5a and 5b are flowcharts for explaining an example of the setting method by the setting unit 25. FIG.
First, in the process of step S101, the operator prepares a 0.5 μL first standard sample containing 5.0 wt% n-heptane and 95.0 wt% ethanol. The “first standard sample” is for calculating the relationship between the n-heptane peak area values A1 and A2 and the concentration in the first FID3 and the second FID7. Here, n-heptane was prepared as a standard component of a plurality of types of hydrocarbon groups added as a modifier to fuel-modified ethanol. As this standard component, not only n-heptane but also general hydrocarbons such as butane and octane can be used.

Next, in the process of step S102, the connection mechanism control unit 21 connects the outlet end of the first column 5 and the first FID 3 based on the operation signal from the input device. 40 three-way solenoid valves 43 are controlled.
Next, in the process of step S103, the first standard sample is separated into n-heptane and ethanol while passing through the first column 5, and detected by the first FID3.
Next, in the process of step S104, the first detector control unit 22 creates a chromatogram with time t versus ion intensity I based on the ion intensity signal detected by the first FID3. Thereby, the peak area value A1 of 5.0 wt% n-heptane in the first FID3 is calculated.

Next, in the process of step S105, the operator prepares 0.5 μL of a first standard sample containing 5.0 wt% n-heptane and 95.0 wt% ethanol.
Next, in the process of step S106, the connection mechanism controller 21 connects the outlet end of the first column 5 and the inlet end of the second column 6 on the basis of the operation signal from the input device. The three-way solenoid valve 43 of the changing connection mechanism 40 is controlled.
Next, in the process of step S107, the first standard sample is separated into n-heptane and ethanol while sequentially passing through the first column 5 and the second column 6, and is detected by the second FID7. The
Next, in the process of step S108, the second detector control unit 23 creates a chromatogram with time t versus ion intensity I based on the ion intensity signal detected by the second FID 7. Thereby, the peak area value A2 of 5.0 wt% n-heptane in the second FID 7 is calculated.

Next, in the process of step S109, the setting unit 25 calculates the sensitivity difference F1 between the first FID3 and the second FID7 using the following formula (1) based on the peak area value A1 and the peak area value A2. And stored in the setting condition storage area 12b.
F1 = A2 / A1 (1)

Next, in the process of step S110, the connection mechanism control unit 21 connects the outlet end of the first column 5 and the inlet end of the second column 6 based on the operation signal from the input device. The three-way solenoid valve 43 of the changing connection mechanism 40 is controlled.
Next, in the process of step S111, the operator prepares a 0.5 μL second standard sample containing 95.0 wt% ethanol and 5.0 wt% n-heptane. The “second standard sample” is used to calculate the relationship between the ethanol peak area value AE and the concentration in the second FID7.
Next, in the process of step S112, the second standard sample is separated into n-heptane and ethanol while sequentially passing through the first column 5 and the second column 6, and detected by the second FID7. The

Next, in the process of step S113, the second detector control unit 23 creates a chromatogram with time t versus ion intensity I based on the ion intensity signal detected by the second FID 7. Thereby, the peak area value AE of 95.0 wt% ethanol and the area value AH1 of n-heptane in the second FID 7 are calculated.
Next, in the process of step S114, the operator prepares a 0.5 μL third standard sample containing 0.5 wt% methanol, 5.0 wt% n-heptane, and 94.5 wt% toluene. . The “third standard sample” is used to calculate the relationship between the peak area value AM and the concentration of methanol in the second FID7.
Next, in the process of step S115, the third standard sample is separated into n-heptane, methanol, and toluene while sequentially passing through the first column 5 and the second column 6, and in the second FID7. Detected.

Next, in the process of step S116, the second detector control unit 23 creates a chromatogram with time t versus ion intensity I based on the ion intensity signal detected by the second FID 7. Thereby, the peak area value AM of 0.5 wt% methanol and the area value AH2 of n-heptane in the second FID 7 are calculated.
Next, in the process of step S117, the setting unit 25 calculates sensitivity correction coefficients αE and αM based on the ethanol peak area value AE and the methanol peak area value AM, and stores them in the setting condition storage area 12b. . Here, αE is a relative sensitivity correction coefficient based on n-heptane of ethanol, and αM is a relative sensitivity correction coefficient based on n-heptane of methanol.
αE = (AH1 / 5.0) / (AE / 95.0) (2)
αM = (AH2 / 5.0) / (AM / 0.5) (3)
In order to set the sensitivity difference F1, sensitivity correction coefficients αE, αM, etc., data is collected and analyzed using the first standard sample, the second standard sample, and the third standard sample, and then calculated on a PC or the like. Sensitivity difference F1 and sensitivity correction coefficients αE and αM calculated by performing the above may be set.

The measurement unit 24 includes the chromatogram created by the first detector control unit 22, the chromatogram created by the second detector control unit 23, and the sensitivity difference F1 and sensitivity correction stored in the setting condition storage area 12b. Based on the coefficients αE and αM, control is performed to calculate the concentration of ethanol and the concentration of methanol in the denatured ethanol for fuel (sample).
Here, a calculation method (hereinafter also referred to as “MDGC method”) in which the measurement unit 24 calculates the concentration of ethanol and the concentration of methanol in the denatured ethanol for fuel will be described. FIG. 6 is a flowchart for explaining an example of the MDGC method.
First, in the process of step S201, the operator prepares 0.5 μL of denatured ethanol for fuel as a sample to be measured. Here, as a pre-process of step S201, in order to obtain the setting start time Ts and the setting end time Te, the fuel-modified ethanol is analyzed using the first column 5 and the first FID 3, and then the processes after step S201. May be implemented.

Next, in the process of step S202, the connection mechanism control unit 21 controls the three-way electromagnetic valve 43 of the flow path changing connection mechanism 40 so as to connect the outlet end of the first column 5 and the first FID3.
Next, in the process of step S203, the denatured ethanol for fuel is separated while passing through the first column 5 sequentially, and detected by the first FID3.
Next, in the process of step S204, the connection mechanism control unit 21 determines whether or not it is the setting start time Ts. When it is determined that it is not the setting start time Ts, the process returns to step S203.
On the other hand, when it is determined that the set start time Ts is reached, in the process of step S205, the connection mechanism control unit 21 connects the outlet end of the first column 5 and the inlet end of the second column 6 so as to connect the flow path. The three-way solenoid valve 43 of the changing connection mechanism 40 is controlled (flow path changing step).

Next, in the process of step S206, the sample is separated while passing through the first column 5 and the second column 6, and detected by the second FID 7.
Next, in the process of step S207, the connection mechanism control unit 21 determines whether or not it is the setting end time Te. If it is determined that it is not the set end time Te, the process returns to step S206.
On the other hand, when it is determined that the set end time Te is reached, in the process of step S208, the connection mechanism control unit 21 connects the outlet end of the first column 5 and the first FID 3 so as to connect the flow path changing connection mechanism. 40 three-way solenoid valves 43 are controlled (flow path changing step).
Next, in the process of step S209, the denatured ethanol for fuel is separated while sequentially passing through the first column 5, and detected by the first FID3.
Next, in the process of step S210, it is determined whether or not to end the measurement. If it is determined not to end the measurement, the process returns to step S209.

On the other hand, when it is determined that the measurement is to be terminated, in the process of step S211, the first detector control unit 22 obtains a chromatogram having time t versus ion intensity I based on the ion intensity signal detected by the first FID3. While creating (refer FIG. 3A), the 2nd detector control part 23 produces the chromatogram which is time t versus ion intensity I based on the ion intensity signal detected by 2nd FID7 (FIG. 4). The measuring unit 24 then detects the peak area value AHCs1 of the hydrocarbon group in the chromatogram created by the first FID3, the peak area value AHCs2 of the hydrocarbon group in the chromatogram created by the second FID7, and the sensitivity difference F1. Based on the above, the peak area value ATs of all hydrocarbons is calculated using the following formula (4).
ATs = AHCs1 × F1 + AHCs2 (4)
Next, in the process of step S212, the measurement unit 24 calculates the concentration of ethanol and the concentration of methanol in the fuel-modified ethanol by the corrected area percentage method (calculation step). Each concentration can be obtained by the following equations (5) and (6).
Ethanol concentration in sample (wt%) = (AEs × αE) / ATs × 100 (5)
Methanol concentration in sample (wt%) = (AMs × αM) / ATs × 100 (6)
Here, AEs and AMs are the peak area value of ethanol and the peak area value of methanol, respectively, in the chromatogram created in the second FID7.
The peaks in the chromatogram (FIG. 3 (a)) created based on the signal of the first FID3 and the peaks other than ethanol and methanol in the chromatogram (FIG. 4) created based on the signal of the second FID7 are All were peaks derived from hydrocarbons. Furthermore, the relative sensitivity correction coefficient of the peak derived from all hydrocarbons was set to 1.

  As described above, according to the gas chromatograph 1 of the present invention, the modified ethanol for fuel is a mixture of a compound group having polarity and a compound group having no polarity. Since a polar liquid phase is applied to the inside of the second column 6, a high decomposition performance can be achieved, and as a result, a low-temperature addition device or the like is not required and it is short. The concentration of ethanol and the concentration of methanol contained in the denatured ethanol for fuel can be calculated in the measurement time (within 10 minutes).

(1) MDGC method (Example)
By using gas chromatograph 1 (Rtx-1 (inner diameter 0.25 mm, length 30 m) as first column 5 and Rtx-WAX (inner diameter 0.32 mm, length 30 m) as second column 6), Samples 1-6 ( Sample) was measured, and the concentrations of ethanol and methanol in Samples 1 to 6 were calculated from the equations (5) and (6). The results are shown in Table 1.
(2) ASTM method (comparative example)
Samples 1 to 6 were measured by a gas chromatograph 51 equipped with a column (Rtx-1) having an inner diameter of 0.25 mm and a length of 150 m, and the relative sensitivity correction of the peak area value AT of all hydrocarbons was performed using the corrected area percentage method. Taking the coefficient as 1, the concentrations of ethanol and methanol in Samples 1 to 6 were calculated. The results are shown in Table 1.

  As shown in Table 1, the measurement results obtained in the examples and the measurement results obtained in the comparative examples almost coincided, and it was confirmed that the measurement accuracy was equivalent.

  INDUSTRIAL APPLICABILITY The present invention can be used for a gas chromatograph or the like that can calculate the concentration of ethanol, the concentration of methanol, and the concentration of a modifying agent in denatured ethanol for fuel.

1, 51 Gas chromatograph 3 First FID (first detector)
5 First column 6 Second column 7 Second FID (second detector)
10, 60 Computer (control unit)
24 Measuring Unit 40 Channel Change Connection Mechanism

Claims (3)

By introducing the sample from the inlet end, the sample is separated into each component fraction, and the first column sequentially discharges the component fraction from the outlet end;
The component fraction is introduced into the interior from the inlet end, whereby the component fraction is separated into each compound, and the second column sequentially discharges the compound from the outlet end;
A first detector;
A second detector connected to the outlet end of the second column;
Using a gas chromatograph provided with a flow path changing connection mechanism to which the outlet end of the first column, the inlet end of the second column, and the first detector are connected, each compound contained in the sample A measurement method for calculating concentration,
The sample is a modified ethanol for fuel which is a mixture of a compound group having polarity and a compound group having no polarity.
A nonpolar liquid phase is applied to the inside of the first column, and a polar liquid phase is applied to the inside of the second column,
The flow path changing connection mechanism connects the outlet end of the first column and the inlet end of the second column so as to circulate, or circulates the outlet end of the first column and the first detector. It is possible to switch to be either connected to
Between the setting start time and the setting end time, the outlet end of the first column and the inlet end of the second column are connected from the flow passage that flows through the outlet end of the first column and the first detector. A flow path changing step for controlling the flow path changing connection mechanism so as to be a flow path for circulation;
Based on the detection signal detected by the first detector and the second detector, viewed including a calculation step of calculating the density and the concentration of methanol of ethanol was contained in said fuel denatured ethanol,
In the calculating step, the peak area value of the denaturant detected by the first detector, the peak area value of the denaturant detected by the second detector, the first detector and the second detector, On the basis of the difference in sensitivity, the peak area value in the second detector of the total modifier contained in the fuel-modified ethanol is calculated,
Based on the peak area value of ethanol and the peak area value of methanol in the second detector on the basis of the peak area value in the second detector of the total modifier, it was contained in the modified ethanol for fuel. A measurement method characterized by calculating a concentration of ethanol and a concentration of methanol . By introducing the sample from the inlet end, the sample is separated into each component fraction, and the first column sequentially discharges the component fraction from the outlet end;
The component fraction is introduced into the interior from the inlet end, whereby the component fraction is separated into each compound, and the second column sequentially discharges the compound from the outlet end;
A first detector;
A second detector connected to the outlet end of the second column;
Using a gas chromatograph provided with a flow path changing connection mechanism to which the outlet end of the first column, the inlet end of the second column, and the first detector are connected, each compound contained in the sample A measurement method for calculating concentration,
The sample is a modified ethanol for fuel which is a mixture of a compound group having polarity and a compound group having no polarity.
A nonpolar liquid phase is applied to the inside of the first column, and a polar liquid phase is applied to the inside of the second column,
The flow path changing connection mechanism connects the outlet end of the first column and the inlet end of the second column so as to circulate, or circulates the outlet end of the first column and the first detector. It is possible to switch to be either connected to
Between the setting start time and the setting end time, the outlet end of the first column and the inlet end of the second column are connected from the flow passage that flows through the outlet end of the first column and the first detector. A flow path changing step for controlling the flow path changing connection mechanism so as to be a flow path for circulation;
A calculation step of calculating the first detector and based on the detection signal detected by the second detector, the concentration and the concentration of methanol of ethanol was contained in said fuel denatured ethanol,
In order to calculate the concentration of ethanol and the concentration of methanol contained in the modified ethanol for fuel in the calculation step, the difference in sensitivity between the first detector and the second detector, the ethanol difference in the second detector A sensitivity correction coefficient indicating a relationship between the concentration and the peak area value, and a setting step for setting a sensitivity correction coefficient indicating the relationship between the concentration of methanol and the peak area value in the second detector. Measuring method. Wherein the inside of the first column, which is 100% dimethyl polysiloxane is applied, the inside of the second column, claim 1 or claim, characterized in that the liquid phase of the polyethylene glycol is applied 2. The measuring method according to 2 .

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