Yokogawa GC1000 Mark II Process Gas Chromatograph - Manual (Page 16)

<1. Principle of Gas Chromatograph >
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IM 11B03A03-01E 3rd Edition : Aug. 23. 2006-00
1. Principle of Gas Chromatograph
A gas chromatograph is an analyzer which first sends a fixed volume of the sampled multi-
component gas mixture to a column, separates it in the column, then measures the con-
centrations of the components with a detector. The process gas chromatograph analyzes
intermittently, allowing periodic analysis in a specified sequence, thus automatic sampling
is possible.
This chapter explains the measurement principle of the GC1000 Process Gas Chromato-
graphs.
1.1 Sampling Mechanism
The process gas chromatograph consists of a sampling mechanism, a column and a
detector.
Sampling is carried out by switching a sampling valve. When separating components or
detecting concentrations, the sampling valve is set to allow the gas (liquid) to be measured
to flow through the sample column. When sampling, the sampling valve leads the gas
(liquid) to be measured to a column on a carrier gas. (See Figure1.1)
There are two important points regarding sampling: a regular volume is sampled since
repeated sampling is required; and samples are taken quickly and securely. The volume is
fixed by measuring a specific gas (liquid) of controlled temperature and pressure using a
sample measurement tube. Samples are taken quickly and securely by ensuring that the
gas to be measured always flows without interrupt.
Sample valve
Electric signal
Vent
Measuring tube
Sample
Carrier gas
Column Detector
Component separation and
concentration detection
Status of sampling
F0101.EPS
Sample valve
Electric signal
Vent
Measuring tube
Sample
Carrier gas
Column Detector
Figure 1.1 Basic Configuration of Gas Chromatograph