JP2002148246A - Gas chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas chromatograph capable of appropriately determining the time to replace a filter mounted to a carrier gas channel 11. SOLUTION: By obtaining pressure at the front part (A point) of the filter 26 from the value (P1) of a primary pressure sensor 22 and the value (ΔP) of a differential pressure sensor 24, pressure at the rear part (B point) of the filter 26 from the value (P2) of a column entrance sensor 16, and the quantity of flow Q flowing through the filter from the values of the primary pressure sensor 22 and the difference pressure sensor 24, filter resistance is computed. It is possible to determine the replacement time from the value of the filter resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph provided with a sample introduction section for sending a sample vaporized by heating a liquid sample to an analytical column, and more particularly to a gas chromatography apparatus provided with a carrier gas in the sample introduction section. The present invention relates to improvement of a carrier gas supply channel provided for supplying.

[0002]

2. Description of the Related Art When a liquid sample is analyzed by a gas chromatograph, a sample introducing section for vaporizing and introducing the sample is used. The material introduction part has a closed space inside, and a septum rubber is attached to the upper part.The sample to be analyzed is sucked into the syringe, and the septum rubber is pierced using this, and inserted into the sample introduction part. Inject the analysis sample. The injected sample is instantaneously vaporized by preheating the sample introduction section by a heating mechanism attached to the sample introduction section. On the other hand, a carrier gas supply channel is connected to the sample introduction section,
The carrier gas (helium, hydrogen, or the like) sent from here allows the vaporized sample to be sent to the analysis column connected to the flow path below the sample introduction unit.

FIG. 1 shows a hardware configuration of a gas chromatograph apparatus. Reference numeral 10 denotes a sample introduction unit, on which a septum rubber is attached. Reference numeral 11 denotes a carrier gas supply flow path for supplying a carrier gas to the sample introduction unit. 12 is an analysis column flow path in which the sample vaporized in the sample introduction part flows into the analysis column together with the carrier gas,
Reference numeral 13 denotes a detector for detecting each component in the sample separated by the analysis column. The sample introduction unit 10 is provided with a split flow path 14 for discharging an excess vaporized sample and a carrier gas separately from the analysis column flow path 12. The split flow path 14 is provided with a split gas control valve 15. By controlling the split gas control valve 15, analysis at an appropriate split ratio (analysis column flow rate: split flow rate) can be performed. Further, the sample introduction unit 10 includes a column inlet pressure sensor 16 for monitoring the internal pressure.

[0004] A cylinder 21 filled with a carrier gas is connected to the carrier gas supply channel 11 by piping. A primary pressure sensor 22 for measuring the pressure of gas supplied from the cylinder, a resistance pipe 23, a carrier gas control valve 25, and a filter 26 are connected in this order along the pipe from the cylinder 21 to the sample introduction unit 10. Further, a differential pressure sensor 24 for measuring a differential pressure generated at both ends of the resistance tube 23 is attached.

The flow rate of the carrier gas flowing through the carrier gas supply flow path 11 can be measured by the primary pressure sensor 22, the resistance tube 23, and the differential pressure sensor 24. These functions as a flow sensor 27. . That is, Q = K * P ₁ * △ between the carrier gas flow rate, the upstream pressure of the resistance tube 23, and the differential pressure measured by the differential pressure sensor.
PQ: Carrier gas flow rate K: Coefficient determined by resistance tube 23 (known amount determined by resistance tube shape) P ₁ :
Pressure upstream of the resistance tube 23 (pressure indicated by the primary pressure sensor 22) △ P: Since there is a relationship of the pressure measured by the differential pressure sensor 24, the carrier gas flow rate is determined by measuring the primary pressure sensor 22 and the differential pressure sensor 24. Q is required.

[0006] A carrier gas control valve 25 provided at the subsequent stage of the resistance tube 23 for controlling a carrier gas flow rate.
Is designed so that the flow rate can be arbitrarily controlled by adjusting the opening degree. The filter 26 provided between the carrier gas control valve 25 and the sample introduction unit 10 includes a carrier gas control valve 25, a differential pressure sensor 24, a primary pressure sensor 2
2. The purpose is to prevent oil components, dirt, and the like generated in the cylinder 21 and the piping connecting them from entering the sample introduction part 10 and to remove the occurrence of ghost peaks. The filter 26 is filled with a fine mesh, a sintered member, or the like, so that foreign substances having a large particle diameter in the carrier gas can be prevented from flowing downstream.

The control unit 28 reads signals from the primary pressure sensor 22, the differential pressure sensor 24, and the column inlet pressure sensor 16,
The carrier gas control valve 25 and the split gas control valve 15 are controlled. Specifically, the flow rate of the carrier gas is calculated from the signals of the primary pressure sensor 22 and the differential pressure sensor 24, and the opening of the carrier gas control valve 25 is adjusted so as to obtain a desired flow rate. Further, the signal of the column inlet pressure sensor 16 is monitored, and the opening degree of the split gas control valve 15 is adjusted so as to obtain a desired pressure.

[0008]

As described above, the carrier gas supply channel is provided with a filter for preventing foreign matter from entering the sample introduction section. As the gas chromatographic analysis is repeated many times, dirt or the like is gradually accumulated in the filter, which may cause clogging. Therefore, it is necessary to replace the filter. Conventionally, there is no particular criterion for the time for replacing the filter, and the user of the apparatus determines the replacement time based on experience. In order to prevent troubles due to clogging during the use of the device, it is common to set the filter replacement time earlier for safety even if the device can be used even now. It is. This replacement is troublesome, and a seal check or the like is required after the replacement. Therefore, it is desirable to reduce the number of replacements as much as possible. For that purpose, it is necessary to accurately determine whether or not the filter needs to be replaced. Therefore, an object of the present invention is to provide a gas chromatograph apparatus which can determine whether or not the filter needs to be replaced based on actual data without any experience, thereby reducing unnecessary filter replacement. or,
SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas chromatograph apparatus having a function of easily determining the necessity of replacing a filter by changing software without changing the hardware of the conventional apparatus.

[0009]

A gas chromatograph apparatus according to the present invention, which has been made to solve the above-mentioned problems, has a sample introducing section for vaporizing a sample, and the analytical column is connected to the sample introducing section. A flow path, a split flow path having a split gas control valve, and a carrier gas supply flow path into which a carrier gas is fed are connected in flow path, and a column inlet pressure sensor for monitoring a column inlet pressure of the sample introduction section is provided, In a carrier gas supply channel, a primary pressure sensor is provided. In a gas chromatograph apparatus provided with a resistance tube provided with a differential pressure sensor for measuring a differential pressure between both ends, a carrier gas control valve, and a filter, a primary pressure is provided. A control having a filter resistance calculating function of calculating a flow path resistance of a filter based on signals from a pressure sensor, a differential pressure sensor, and a column inlet pressure sensor. Characterized by comprising a part.

Whether or not the filter needs to be replaced can be determined from the magnitude of the pipe resistance of the filter. In general, the relationship among the flow path resistance, the flow rate, and the differential pressure in a pipe has a relationship substantially similar to the relationship between the electrical resistance, current, and voltage in an electric circuit. Therefore, in the same way as the electric resistance, the flow path resistance can be calculated by calculating the approximate value of the pipe resistance by dividing the pressure difference (corresponding to the voltage difference) at both ends of the pipe by the flow rate (corresponding to the current) flowing through the pipe. . Therefore, if the pressure value at the front and rear positions of the filter and the flow rate value flowing through the filter are known, the resistance of the filter can also be determined. By determining the necessity of replacement of the filter based on this value, the necessity of replacement without removing the filter Can be accurately determined.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a hardware configuration of a gas chromatographing apparatus showing one embodiment of the present invention. The hardware configuration used to carry out the present invention is the same as that of the conventional device, and a description thereof will be omitted. The feature of the present invention lies in the software configuration executed in the control unit 28.

Next, the principle of calculating the filter resistance executed in the present invention will be described with reference to the block diagram shown in FIG.
When obtaining the filter resistance, the carrier gas is flowed at an appropriate flow rate, and the carrier gas control valve 2 is set in advance.
5 is fully opened so that the pipe resistance by this valve can be ignored. Subsequently, an appropriate pressure is generated in the sample introduction section by narrowing the opening of the split gas control valve 15 (that is, the flow rate of the carrier gas supplied from the carrier gas supply flow path 11 to the sample introduction section, the flow rate of the analysis column flow path, and the like). constant pressure P ₂ is generated in the split flow channel 14 the sample introducing section 10 in relation to the gas flow discharged from) the value P ₂
Is monitored by the column inlet pressure sensor 16. Since piping resistance from the filter 26 to the sample inlet is negligible, (B point in FIG. 1) filter 26 rear pressure P _B of the position can be regarded as P _{B =} P _2.

The pressure at the position in front of the filter 26 (point A in FIG. 1) is determined as follows. That is, upstream of the point A, the resistance pipe 23 and the carrier gas control valve 25 exist as elements that cause a pressure gradient due to the pipe resistance. Then, the pressure value P ₁ on the upstream side of the resistance tube 23 is obtained by the primary pressure sensor 22. Here, since the carrier gas control valve 25 is fully opened as described above so that no resistance is generated, no pressure gradient is generated in this portion. Therefore, only the pressure gradient ΔP generated at both ends of the resistance tube 23 occurs. Therefore, the pressure at point _A is P _A = (P ₁ − △
P).

The flow rate flowing through the filter 26 is determined as follows. That is, the flow rate flowing through the filter 26 is equal to the flow rate flowing through the resistance tube 23. As mentioned earlier the primary pressure pressure sensor 22, the resistance tube 23, in combination with a differential pressure sensor 24 functions as a flow sensor for measuring the flow rate through the resistance tube 23, the flow rate Q = K * P ₁ * ΔP can be obtained.

[0015] or more filter resistor Rf from _{it, Rf = (P A -P B} ) / Q = - be calculated as _{(P 1 △ P-P 2} ) / K * P 1 * △ P (1) it can. By determining that the filter replacement time has arrived when this value becomes larger than a predetermined reference value, it is possible to appropriately determine the correct replacement time.

FIG. 3 is a flowchart showing the flow of calculating the filter resistance in the present invention. First, the stopper of the cylinder 21 is opened to flow the carrier gas (st1), and the carrier gas control valve 25 is fully opened (st2). Further, an appropriate pressure is generated in the sample introduction unit 10 by squeezing the split gas control valve 15 (st3). In this state, the respective pressures of the primary pressure sensor 22, the differential pressure sensor 24, and the column inlet pressure sensor 16 are read (st4), and the filter resistance Rf is calculated based on these values by the equation (1) (st).
5). The calculated result is displayed on a CRT screen (not shown) connected to the control unit to inform the analyst whether the filter needs to be replaced (st6). The control unit may store in advance a reference value of the filter resistance as a reference for the replacement time, and display an alarm when the reference value is reached.

[0017]

As described above, in the gas chromatograph apparatus of the present invention, the primary pressure sensor, the differential pressure sensor,
Since the filter resistance can be calculated from the pressure value of the column inlet sensor, it is possible to determine appropriate filter replacement time by referring to this value. In particular, with regard to the hardware configuration, the filter resistance can be calculated without any addition to the conventional device, so that the function can be added without increasing the cost of the device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hardware configuration of a gas chromatograph device.

FIG. 2 is a block diagram showing a configuration for calculating a filter resistance according to an embodiment of the present invention.

FIG. 3 is a flowchart for calculating a filter resistance according to an embodiment of the present invention.

[Explanation of symbols]

Claims (1)

[Claims] 1. A sample introduction section for vaporizing a sample, an analysis column flow path to which an analysis column is connected, a split flow path having a split gas control valve, and a carrier gas supply into which a carrier gas is fed. The flow path is connected to the flow path, and a column inlet pressure sensor for monitoring the column inlet pressure of the sample introduction section is provided. The carrier gas supply flow path includes a carrier gas source, a primary pressure sensor, and a differential pressure between both ends. In a gas chromatograph equipped with a resistance tube provided with a differential pressure sensor to be measured, a carrier gas control valve, and a filter, the flow path resistance of the filter is determined based on signals from a primary pressure sensor, a differential pressure sensor, and a column inlet pressure sensor. A gas chromatograph apparatus comprising a control unit having a filter resistance calculating function of calculating a filter resistance.