Gas chromatography: How does it work

What is a gas chromatograph?

Let’s talk about that 7890B gas chromatograph. The gas chromatograph has an inlet, detector, oven, power switch, Operating panel, the detector cover, detectors, keypad Oven exhaust vent, inlet Vents, gas supply connections, electronic cable connections, oven cooling intake, power connection.

Gas chromatography

Gas chromatography

Gas chromatography
Overview of Gas chromatography 7890B Model manufactured by Agilent corporations

The inlets

The inlets inject samples into the GC. The samples can be injected by automatically sampling device.

Automatic injectors (ALS)

The most important part of gas chromatography is the sample injections into the inlet‘s by an automatic sampling device and that automatic sampling device is called the automatic liquid sampler (ALS) or headspace sampler or by hand using a Syringe.

Automatic injectors have some component like auto-injector turret, sample tray, barcode reader.

Automatic injectors with a sample tray and barcode reader automate the liquid sample processing Including the basic sample preparation.

 The GC column and oven

GC columns are located inside a temperature controlled oven.  One end of the column is attached to the inlet while the other end attaches to the detector. The length of the column, diameter and internal coating can vary. Each column is designed for the use of different compounds and different purposes.

The column and open is used for separating the injected sample into the individual component as the sample travels through the column.

The temperature controlled over is used to speed up the sample flow through the column to separate the injected sample perfectly.

Samples are separated based on their molecular weight and the heavier molecule will travel slowly and the lighter molecules will travel fast through the 30m long column to be detected to the detector.


Detectors identify the presence of compounds as they exist in the column as each compound enters the detector, the detector generates an electrical signal proportional to the amount of compound present. This signals generally sent to a data analysis system to make chromatogram.

The 7890B GC can accommodate three internal detectors in it.



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