PAH's and VOC's by static headspace

[Beetle Juice]

Hello,
Has anyone ever developed a method that allows for the seperation of volatile organic compounds and polycyclic aromatic compounds using static headspace on the same column (RTX volatiles), with an LOD of 0.1ppb. Can it be done? My current method for VOC's in aqueous samples has a run time of 36 minutes and can seperate 59 VOCs and ramps to a temperature of 180*C. Would having a slower ramp to say 270*C and an isothermal hold be enough to get the PAH's through the column or are they not volatile enough to be extracted by the headspace?

[Karen01]

Hello,
Has anyone ever developed a method that allows for the seperation of volatile organic compounds and polycyclic aromatic compounds using static headspace on the same column (RTX volatiles), with an LOD of 0.1ppb. Can it be done? My current method for VOC's in aqueous samples has a run time of 36 minutes and can seperate 59 VOCs and ramps to a temperature of 180*C. Would having a slower ramp to say 270*C and an isothermal hold be enough to get the PAH's through the column or are they not volatile enough to be extracted by the headspace?

I can't answer your questions, but I have some for you...

Are you looking at alkanes? If so what is the highest alkane (carbon number) you are looking at, and is your matrix aqueous?

Thanks,
- karen

[Spuzzin]

The issue is going to be getting the PAHs into the headspace. Naphthalene is the first of the PAH16 compounds and one of the last compounds in a 'normal' VOC suite and the response of naphthalene is usually lower than that of the the other VOCs in static headspace techniques. You could possibly do a few of the earlier PAHs using dynamic headspace or MHE. Another alternative which I've seen but never used it incubate the sample onto a thermal desorbtion tube. Obviously this requires specialist instrumentation.

Rich

[Davide]

I conducted PAHs analyses and these type of compounds require very high temperature. The injector temperature is generally higer than 300°C. So I think it would be difficult to extract them from water by HS. I recommend you to recover these compounds by SPE or even MIP cartiges then to elute them in toluene. Finally, to develop a dedicated method.

[Beetle Juice]

I can't answer your questions, but I have some for you...

Are you looking at alkanes? If so what is the highest alkane (carbon number) you are looking at, and is your matrix aqueous?

Thanks,
- karen[/quote]

Hi, I don't really look at alkanes by headspace but I have seen icosane (C20) and others in water and solid matrices. Anything below C15 should be good anything above C22 difficult, most probablly due to low volatility at headspace equilibrium temperatures, I use 85*C for 10 minutes for aqueous samples.
Hope that helps..