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Next: 4 Operational and Maintenance Up: Gas Chromatograph Buyer's Guide Previous: 2.5 Data Systems

3 Physical Plant Requirements

The GC system has a typical footprint of about 30 inches square. The optional computer system will usually consist of a CPU unit, keyboard, mouse, monitor and printer. If additional components, such as an autosampler, headspace sampler, purge and trap unit or cryotrap unit is used, additional bench space will be required for the components and associated controlling electronics.

Power requirements vary for different manufacturers and even different models. Some instruments operate on normal 15 Amp 120 V AC, but some require 20A 120 V AC, and still others require 13 or 15 A 220 V AC. As much of the system is electronic, the system components last longer and are more reliable with so-called clean power; that is, the use of adequate surge protectors is recommended. Some users also install Uninterrupted Power Supplies to further protect the computer system if installed.

The system will require approximately 50 psi carrier gas for the chromatography system. Unless there is some compelling reason to use another gas, most gas chromatograph users use high grade (also called 5.0) helium, though some applications require hydrogen (with all its associated safety considerations), nitrogen or even other gases. Even with the use of high grade carrier gas, inline moisture and oxygen traps are the minimum recommended additional treatments. Triple Filters that scrub oxygen, moisture and general hydrocarbons can be obtained in a single unit. These units have replaceable filters that can be changed without opening the carrier gas line to atmosphere.

In addition to the carrier gas, other gas supplies may be required. For example, an FID requires hydrogen and air. These can be supplied via compressed gas, or with gas generators. Other components, such as desorbers, may have specific gas requirements.


next up previous
Next: 4 Operational and Maintenance Up: Gas Chromatograph Buyer's Guide Previous: 2.5 Data Systems
John S. Riley, DSB Scientific Consulting