Yokogawa GC8000 Process Gas Chromatograph - Manual (Page 430)

<Appendix A Principle of Gas Chromatograph>
App.A-1
IM 11B08A01-01E
Appendix A Principle of Gas Chromatograph
A gas chromatograph is an analyzer which fi rst sends a fi xed volume of the sampled
multicomponent gas mixture to a column, separates it in the column, then measures the
concentrations of the components with a detector. The process gas chromatograph analyzes
intermittently, allowing periodic analysis by a specifi ed method, thus automatic sampling is
possible.
This chapter explains the measurement principle of the GC8000 Process Gas Chromatograph.
 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 fl ow 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)
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 fl ows without interrupt.
Sample valve
Electric signal
Vent
Measuring tube
Sample
Carrier gas
Column Detector
Component separation and
concentration detection
Status of sampling
F_A01.ai
Sample valve
Electric signal
Vent
Measuring tube
Sample
Carrier gas
Column Detector
Figure 1 Basic Confi guration of Gas Chromatograph
2nd Edition : May 11, 2012-00
App.A