Chromatography Forum

Dear friends,

salve salve!!

I'd like to know whether you, who have been working in chromatography for years, know any preparation technique to ease the process of analysis of dense oils, according to some papers, this oil shall contain the following chemical families:

aldehydes: formaldehyde, acetaldehyde
organic acids: formic acid, propionic acid, acetic acid...
phenols: phenol, m-cresol, eugenol etc
Ketones: acetone, cyclopropanone
Amines
Alkanes
and traces of others.

This oil is obtained from pyrolysis of nappier grass.

Any comment will be very much appreciated.

Marcio

I see multiple options for a prefractionation, for example. Techniques of that nature have been applied to other complex matrices, such as food or blood or urine. For example, acids and bases (amines) can be capture on either cation exchangers or anion exchangers and then analyzed separately.

Also, selective derivatization can permit a selective analysis of a group of compounds. For example, aldehydes and ketones react with hydrazines such as phenyl hydrazine or better dinitrophenyl hydrazine and can be detected selectively.

I did something similar to your work for my masters degree. We were looking at crude oil fractions using a variety of spectroscopic techniques. The first step for us was to do fractionation on alumina columns which seperate saturated hydrocarbons, aromatic hydrocarbons, more polar compounds and asphalts (insoluble compounds). Most of the compounds that you have mentioned would elute with the polar fraction. However, amines may be permanently sorbed to the column. Ion exchange resins could be used to isolate acidic and basic fractions. The trick is that a typical ion exchange resin depends on a mostly aqueous solvent mix to work while oil fractions are essentially insoluble in water or even methanol / acetonitrile.

What type of information are you hoping to acquire? NMR is a great tool for crude oil analysis (especially 13C NMR). GPC can be useful also for a quick test of molecular weight composition. Mass spec also gives molecular weight information and has the advantage (or disadvantage!) of selective detection depending on instrument and source conditions.

Crude oil and nappier grass? There is more lit. on lipids than one can handle, I wouldn´t bother with mineral oil on top of it.