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pH adjustment
Posted: Tue Feb 12, 2013 10:24 am
by fractionated
Why do we need to adjust the pH of the liquid sample to less than 2 prior to hydrocarbon extraction?
Thank you
Re: pH adjustment
Posted: Tue Feb 12, 2013 2:32 pm
by Johnny Rod
Either to protonate acidic species and make them hydrophobic so they extract into the solvent, or to make basic species ionised to keep them in the water phase. So it depends what you're trying to achieve.
Re: pH adjustment
Posted: Wed Feb 13, 2013 1:47 pm
by Don Shelly
Johnny Red is correct. In the case of heavy fuels such as Diesel and kerosene, you are protonating fatty acids.
Re: pH adjustment
Posted: Fri Feb 22, 2013 10:38 am
by fractionated
thank you for your reply. But why do we have to include fatty acids in TPH extraction when the aim is to extract the hydrocarbons present in the liquid samples?
Re: pH adjustment
Posted: Fri Feb 22, 2013 9:12 pm
by Don Shelly
If your goal is to extract fuel, fatty acids are part of that fuel.
Re: pH adjustment
Posted: Tue Mar 19, 2013 3:17 am
by fractionated
thanks for the reply. To my understanding, fatty acids are one of the metabolic products of hydrocarbon degradation my microorganisms. if we include them in the total hydrocarbon extraction, will this not create a bias in measurement?
Re: pH adjustment
Posted: Tue Mar 19, 2013 3:23 am
by Don Shelly
Some refineries actually add fatty acids to the heavy fuels that that produce. I have no idea why. Try extracting a "fresh" diesel fuel with and without pH adjustment and you will see for yourself.