JP2005274416A - Gas chromatograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas chromatograph capable of saving time and labor, and efficiently setting the pressure of a carrier gas. <P>SOLUTION: The gas chromatograph is constituted, in such a way that the carrier gas passed through a column system 1 is branched to a main detector 6 and a sub-detector 8 at a branch point 7, and is provided with pressure control parts 4a and 4b each for restricting the downstream-side pressure of a column, immediately in front of the branch point 7 and the pressure of the branch point 7. The quantity of flow of the carrier gas through each channel, before and after the branch point 7, is computed and displayed by a prescribed computational expression on the basis of pressure setting values inputted to the pressure-control parts 4a and 4b by an operator. Since the quantity of flow through each channel is immediately accordingly displayed, when the settings of the pressure control parts 4a and 4b are changed by the operator by this constitution, the operator can speedily set the pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas chromatograph that analyzes, for example, odor components in foods and fragrances.

FIG. 2 shows an example of a flow path configuration of a conventional gas chromatograph configured for odor component analysis.
In the figure, a carrier gas supplied from a carrier gas cylinder 5 is adjusted to a predetermined pressure by a pressure control unit 4a, passes through a sample introduction unit 3, passes through a column system 1, and is a main detector 6 (for example, a mass spectrometer). The flow path is configured to flow through A sub-detector 8 (for example, a sniffing device) is provided on a branch path that is separated from this flow path at a branch point 7 provided in the front stage of the main detector 6.
In this case, the column system 1 is composed of a single column in the simplest case, but in many cases is composed of a plurality of columns and a switching mechanism (not shown) for switching them, and further, in an intermediate stage. In some cases, a monitor detector (not shown) is used for viewing the separation status.
The scent sniffing device is also called a sniffer or sniffing port, and is a funnel-shaped instrument for detecting an odor component by an operator's own sense of smell.

Analysis by the apparatus configured for odor component analysis as described above is performed as follows.
Similar to a general gas chromatograph mass spectrometer, a sample is introduced from the sample introduction unit 3, the target component is separated from the front and rear contaminant components by the column system 1, and is detected by the main detector 6 (mass spectrometer) to be qualitative or In parallel with this, the operator detects the target component by using his / her own olfaction using the sub-detector 8 (smell sniffer).

  When the column system 1 is composed of a plurality of columns, in order to switch between them, a gas whose pressure is appropriately adjusted (referred to as a makeup gas) is placed near the branch point of the flow path without directly switching the flow path with a valve or the like. A method called Deans switching is used in which the flow is switched by changing the pressure balance. An analysis method for switching a column during analysis by this method is also called multi-dimension gas chromatography, and is described in Patent Document 1 as a prior art. In FIG. 2, the case where the column system 1 is composed of a single column is illustrated as the simplest case, but the apparatus for analyzing odor components is configured as a multi-dimension gas chromatograph as described above. There are many cases.

Japanese Patent Laid-Open No. 11-31620

In a gas chromatograph having a branch path in the carrier gas flow path as in the above-described conventional apparatus, in order to appropriately set the flow rate of each branched flow path, the flow rate is actually measured using a flow meter downstream of each flow path. While measuring, it was necessary to change the set pressure little by little and obtain an appropriate value by cut and try. This is a cumbersome and time-consuming work, and particularly when the column system is configured as a multi-dimension gas chromatograph, the number of branch paths increases, and the complexity is considerable.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a gas chromatograph capable of efficiently setting a carrier gas pressure while saving time and effort.

  In order to solve the above-mentioned problems, the present invention provides a gas chromatograph configured such that a carrier gas that has passed through a column system is divided into two detectors at a branch point, and a pressure upstream of the column immediately before the branch point. And a pressure control unit that regulates the pressure at the branch point respectively, and the carrier gas flow rate of each flow path before and after the branch point is calculated by a predetermined calculation formula based on the pressure setting value input by the operator to the pressure control unit And configured to display.

  Since the present invention is configured as described above, when the operator changes the setting of the pressure control unit, the flow rate of each branch path is displayed accordingly, so that the operator can perform the desired measurement without performing cumbersome flow rate measurement. The pressure control unit can be quickly set so that the flow rate is as follows.

FIG. 1 shows an embodiment of the present invention. In the figure, the same components as those in FIG.
The present embodiment differs from the conventional example shown in FIG. 2 in the flow path configuration in that the same type of gas as the carrier gas adjusted to the pressure P1 by the pressure control unit 4b is supplied to the branch point 7. is there. As a result, the pressure at the branch point 7 is forcibly maintained at P1 even if the carrier gas flow rate changes. In other words, the pressure at the branch point 7 is regulated by the pressure control unit 4b.
When the column system 1 is composed of a single column, the pressure on the upstream side of the column immediately before the branch point 7 is also regulated by the pressure control unit 4a in the same sense and maintained at the pressure P0 (the resistance is almost not increased). The pressure before and after the sample introduction part 3 without it can be regarded as the same P0).

In this state, the carrier gas flow rate of each flow path around the branch point 7 can be expressed by the following equation derived from the Poiseuille equation.
F0 = K0 × (P0 + 2P1) × P0 (1)
F1 = K1 × (P1 + 2Pa) × P1 (2)
F2 = K2 × (P1 + 2Pv) × P1 (3)
Here, F0: Flow rate flowing in the column immediately before the branch point 7 F1: Flow rate flowing in the sub-detector 8 F2: Flow rate flowing in the main detector 6 Pa: Atmospheric pressure Pv: Vacuum pressure in the main detector 6 (mass spectrometer) K0 , K1, K2: coefficients determined by resistance, temperature, etc. of each flow path.

Reference numeral 2 in FIG. 1 denotes a flow rate calculation display means using a computer.
In the above equations (1), (2), and (3), P0 and P1 are pressures adjusted by the pressure control units 4a and 4b, respectively, and the values are input by the operator from the keyboard (not shown). The set values p0 and p1 are configured to be input to the flow rate calculation display means 2 at the same time. K0, K1, and K2 can be obtained by back-calculating from the measured values of the flow rate of each flow path, Pa is a physical constant, and Pv is determined by the specifications of the mass spectrometer, so these values are input to the computer. If stored, each flow rate value can be calculated and displayed by the above equations (1), (2), and (3).

There is no need to newly prepare a computer used in the flow rate calculation display means 2 in this case. Since recent gas chromatographs are comprehensively controlled by a built-in computer, some of the functions of the computer can be used as the flow rate calculation display means 2. That is, the flow rate calculation display means 2 in this case does not exist as hardware, and may be considered to be configured by software.
Since K0, K1, and K2 are functions of temperature, it is necessary to input a temperature value to the computer in order to calculate the equations (1), (2), and (3). The temperature value already taken into the computer can be used for temperature control.

The above is a description of the case where the column system 1 is composed of a single column, but the present invention can also be applied to the case of multi-dimension gas chromatography in which a plurality of columns are switched for analysis.
In that case, a configuration similar to that of the pressure control units 4a, 4b is added, and makeup gas for switching the flow path is supplied through this. Since the pressure of this makeup gas regulates the upstream or downstream pressure of the column before and after the switching point, an equation similar to the equation (1) is established for the column, and that equation is used before and after the switching point. It is possible to calculate and display the flow rate flowing through the column or branch.

It is a figure which shows one Embodiment of this invention. It is a figure which shows the conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Column system 2 Flow rate calculation display means 3 Sample introduction part 4a Pressure control part 4b Pressure control part 5 Carrier gas cylinder 6 Main detector 7 Branch point 8 Sub detector

Claims (2)

  In the gas chromatograph in which the flow path is configured so that the carrier gas that has passed through the sample introduction part is diverted to the main detector and the sub-detector at the branch point after passing through the column system including one or more columns. A pressure control unit that regulates the upstream pressure of the column immediately before the branch point belonging to the system and the pressure at the branch point to a set value input by an operator, and a predetermined calculation formula based on the set value to the branch point. A gas chromatograph comprising flow rate calculation display means for calculating and displaying a flow rate of a carrier gas flowing in each communicating channel.   The gas chromatograph according to claim 1, wherein the main detector is a mass spectrometer and the sub-detector is an odor device.

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