Chromatography Forum

we are looking to extract PAHs from soil using Dichloromethane (DCM). I was advised to use 2-fluorobiphenyl as Internal standard.

I have a standard curve setup for PAHs. Should I do a standard curve for Internal std. separately and analyse the data file with that method.

Please guide me.

Thanks,
Jason

It really depends on which PAHs you are analyzing for and what type of detector. For EPA method 8270 I was usually analyzing the EPA 16 priority PAHs and this method uses an MS detector. I was using an internal standards mix from Restek which contained deuterated analogs of about 6 PAHs http://www.restek.com/catalog/view/5732. If you are using FID or some other detector then 2-fluorobiphenyl will probably work well for the early eluting (lighter mass) PAHs. You may need another IS or two or three for the later eluting ones. They all respond completely different but mostly based on mass/volatility after multiple injections.

Restek also has an MS surrogate solution that contains 2-fluorobiphenyl along with 3 deuterated compounds. http://www.restek.com/catalog/view/6631

Let me know if you have other questions.

Mr. Jason Bourne,

Sorry if forgot to respond to the calibration part of your question.

I would create a new set of calibration mixtures with your IS (2-fluorobiphenyl and/or others) at a fixed concentration in each standard. So you might have your PAHs at let's say 5, 10, 20, 30, and 50 ppm in five different vials and you would have your IS concentration at a fixed value of lets say 20 ppm in each vial. You will generate a curve using Response Factors (RFs) for the analytes response over the IS response. You will then spike the IS into each sample you analyze making sure that the final concentration in your sample is exactly 20 ppm. This way the IS corrects for sample transfer losses, volatilization etc. I apologize if you already know this but I wanted to cover all bases.

If you need more information on this or more specific details it might be easier over email and I might be able to send you some files that explain it better.

tlahren,

I am a beginner so. that info was very helpful.

Thank you