Partition Coeffecient

[ziarehmann]

Hi,

In the headspace chromatography, from the area of peaks we can calculate the concentration of a compound in solution using the formula Area= Co/(K*ß). Co= concentration
K= Partition coeffecient
ß = phase ratio.

How or where can i find the partition coeffecients of different fatty acids i.e. acetic acid; propionic, iso-butyric, butyric, iso valeric, valeric and caporic acid.

Thanks for your help.

Regards!
Zia

[Peter Apps]

Hi Zia

Try google, but even if you find them it is not going to provide an accurate measure of concentration because the coefficients are extremely sensitive to pH, and so the presence of other acids in your samples will invalidate the results.

Peter

[ziarehmann]

Ok, Then howcome can i relate my area of peaks with the concentration in the liquid phase. or preciseouly saying how can we quantify the results of headspace into original concentration?

[Peter Apps]

As in your other thread, you need to acidify the samples with a strong acid, so that the presence or absence of weak acids does not affect the pH. This will also increase your peak areas by pushing the weak acids into the headspace.

Then you run a calibration by measuring peak areas for different known concentrations of your organic acids made up as standards (in dilute strong acid the same as you use for your samples). Then you use the calibration to calculate form sample peak area to concentration.

Since your method is not repeatable I would suggest running both standards and samples in triplicate and working with the means of the triplicates.

Peter