JPH04130269A - Gas chromatograph - Google Patents

Abstract

PURPOSE:To keep the flow rate of the carrier gas flowing to a column constant by calculating the new flow rate of the carrier gas from the change of the pressure detected by a pressure sensor, the resistance of a column flow path and the resistance of a septum flow path and renewing the set value of a flow controller on the basis of the new flow rate value. CONSTITUTION:For example, at the time of temp. rise analysis, the new flow rate of carrier gas is calculated corresponding to the change of the input pressure of a column 1 detected at every definite time by a pressure sensor 5 and the resistance of a column 1 and a septum purge 2 in an electric control part (CPU) 6. The control part 6 renews the flow rate of the carrier gas until now to the new flow rate thereof to set the new flow rate to a flow controller 4. The flow controller 4 supplies the carrier gas to the column 1 in the new flow rate to compensate the lowering of a column flow rate accompanied by an increase in the resistance of the column due to a temp. rise and performs control so as to keep the column flow rate constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a gas chromatograph, particularly a gas chromatograph including a septum purge.

(B) Conventional technology Conventionally, in order to keep the column flow rate constant, gas chromatographs including a septum barge are equipped with a pressure regulator that can keep the column input pressure constant, or a flow controller that can control the carrier flow rate. There is.

(c) Problems to be Solved by the Invention In the conventional gas chromatograph described above, it is possible to keep the gas flow rate constant on the input side, but for example, due to temperature rise analysis, the column resistance changes and the column flow rate changes. No measures were considered to deal with the changes.

The present invention has been made in view of the above-mentioned problems, and provides a gas chromatograph in which the flow rate of carrier gas flowing through a column can be kept constant even if the flow path resistance of the column changes due to a change in column temperature. It is intended to.

(d) Means and Effects for Solving the Problems The gas chromatograph of the present invention includes a septum purge flow path, receives a carrier gas, electrically controls the carrier gas, and controls the column and septum purge flow path. a flow controller that supplies the flow to the column; a pressure sensor that is provided at the front stage of the column and detects the column inlet pressure;
Electrical control that calculates a new carrier gas flow rate based on the change in pressure detected by this pressure sensor, column flow path resistance and septum flow path resistance, and updates the set value of the flow controller to this new carrier gas flow rate value. It has a section.

In this gas chromatograph, for example, during temperature rise analysis, a new carrier gas flow rate is updated at regular intervals based on changes in column input pressure detected by a pressure sensor and the previous carrier gas flow rate. Then, a new flow rate of carrier gas is supplied to compensate for the decrease in column flow rate due to an increase in column resistance due to temperature rise, and control is performed so that the column flow rate is always constant.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a schematic diagram showing the configuration of a gas chromatogram showing an embodiment of the present invention. In the figure, 1 is a column, 2 is a septum barge, 3 is an injector that injects a sample, 4 is a flow controller that receives carrier gas and electrically controls the flow rate of carrier gas input to the column, and 5 is a column inlet. The pressure sensor 6 that detects the pressure P calculates a new carrier gas flow rate according to the change in the expansion pressure P of the pressure sensor 5 and the resistance of the column 1 and the septum purge 2, and sets this in the flow controller 4. This is the electrical control section. The electrical control unit 6 is composed of, for example, a CPU (computer).

In this gas chromatogram, a process for controlling the column flow rate to a constant value when increasing the temperature of the column by to will be described.

Here, the column input pressure is P1, the column resistance is R3, the column flow rate is Ill, the septum purge resistance is R2, and the septum purge flow rate is u2. Also, the carrier gas flow rate U is u
=u, +u=.

At the start of temperature rise (1=0) In, The column input pressure P is t.

To the paper machine, Column resistance is RI +ΔRI Then, Assume that the column input pressure becomes P+ΔP as a result of this.

At this time, From equations (1) and (2) above, Transforming equation (1), year, Inserting this into equation (3), we get becomes.

Than this by the way, t.

column flow rate of ul becomes.

This column flow rate u.

Column flow at the start of heating amount Carrier gas flow rate be.

i.e. Pi K.

-ΔI’ll.

PX - ΔF. However, x=Rz/R+ Therefore, the carrier gas flow rate can always be kept constant at the time interval to. It shows the relationship between time after the start of temperature increase and column flow rate. The time interval can also be kept approximately constant by making it short enough to ignore minute changes in the column flow rate U.

In the above equation (7), R, and R are the column resistance and septum purge resistance before the start of temperature rise, so they are known and stored in the memory of the electric control unit 6 in advance. Therefore, the electric control unit 6 sets a new flow rate in the flow controller 4 based on the carrier gas flow rate U and the change ΔP in the column input pressure P, which is the monitored value of the pressure sensor 5.

(F) Effects of the Invention According to this invention, in temperature-programmed analysis, a new carrier gas IIT is set in the flow controller based on the input pressure change from the pressure sensor, taking into account the increase in column resistance due to temperature increase. , the column if can be kept constant, and analysis can always be performed under the optimum column conditions.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a gas chromatograph including a septum purge, and FIG. 2 is a diagram showing the relationship between the passage of time and column flow rate during ascending analysis of the gas chromatograph. 1: Column, 2: Septum purge, 4: Flow controller, 5: Pressure sensor, 6: Air control section.

Claims (1)

[Claims] (1) In a gas chromatograph that includes a septum purge channel, there is a flow controller that receives carrier gas, electrically controls this carrier gas, and supplies it to the column and septum purge channel, and a flow controller that is installed at the front stage of the column and controls the column inlet pressure. A new carrier gas flow rate is calculated based on the pressure sensor to be detected, the change in pressure detected by this pressure sensor, the column flow path resistance, and the septum flow path resistance, and the flow controller is set to this new carrier gas flow rate value. A gas chromatograph characterized by comprising: an electric control unit that updates values;