Usage of GC

Chromatography Forum: GC Archives: Usage of GC
Top of pagePrevious messageNext messageBottom of pageLink to this message  By gohtb on Monday, November 8, 1999 - 09:19 am:

Is GC can only be use to analyse volatile compound
? By derivatization ,can GC be used to analyse non volatile compound


Top of pagePrevious messageNext messageBottom of pageLink to this message  By lisa on Monday, November 8, 1999 - 03:27 pm:

if you derivatize a compound, you will usually make it MORE non-volatile. You can't analyze a compound by GAS chromatography unless you can get it into the GAS phase :)
Lisa


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Bruce Freeman on Tuesday, November 9, 1999 - 06:16 am:

Some derivatives are indeed more volatile than the parent molecules. Fatty acid methyl esters ("FAME") are one well-known example. Silanation reagents are also used to produce volatile derivatives.
Before assuming that derivatization is necessary, however, it is worth checking the literature. Many "non-volatile" compounds are really quite amenable to GC analysis. The reason is that GC temperatures are high and quantities are exceedingly low. A compound will be completely swept out of a GC injection port well below its boiling point because it has a significant vapor pressure well below the boiling point. You can check Perry's Handbook of Chemical Engineering for a table of vapor pressures versus temperaturs for many organic compounds.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Jason Ellis on Thursday, November 11, 1999 - 10:05 am:

GC can be used to analyze nonvolatile compounds. I know people who perform high-temperature simulated distillation of crude oil fractions which contain hydrocarbons up to about C110. Obviously this would be an extreme case, however by using certain injection techniques (i.e. cool-on-column, PTV), thin film columns, and metal or high-temperature fused silica tubing we can reliably analyze nonvolatile organic compounds such as hydrocarbons, triglycerides, polymer additives, etc. Derivitization can definitely help in some of these nonvolatile applications, depending upon the nature of the compound.


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