Appendix a principle of gas chromatograph, App.a-1, Sampling mechanism – Yokogawa GC8000 Process Gas Chromatograph User Manual

Page 430: App.a

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

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