Normalization of peaks to surrogate standard

[fractionated]

I measure the PAH concentrations using GC-FID. Prior to extraction I added phenanthrene d-10 as a surrogate standard. I have a recovery of about 70%. Does it mean that in reporting, all area of the peaks of target PAHs should be increased or adjusted to 30% since we know that in actual sample most likely 30% of the PAHs were not extracted or lose during the analysis? Are surrogate standard for reference only or usually used for quantification? I am currently doing manual integration since I am not yet familiar with the software. Any help will be appreciated. Thank you

[James_Ball]

I guess it would be dependent on what protocols you must follow. When running under EPA methods you do not correct values for surrogate recovery but report the surrogate recovery along with the target analyte results, then the end user is to evaluate the quality of the data from the given information.

The problem with using a single surrogate to correct for extraction efficiency is you must assume that all target analytes respond to the extraction procedure in exactly the same way. If Naphthalene is more easily extracted than phenanthrene-d10, then you will over correct that value.

Some method require that you extract an internal standard used to quantify the target analytes, but with those you are also required to extract all of your calibration standards so that they see the same extraction effects as the samples.

[fractionated]

Thank you James for very helpful reply. I should follow the results then based on the obtained value and just indicate the percentage recovery in my report. It is true that the recovery may vary from compounds to compounds in a span of the 16 priority PAHs. I am planning to use acenapthene-d10, phenanthrene-d10, and perylene-d12 for surrogate recovery. This time I am planning to analyze using GC-MS. Im still looking for a good internal standard for quantification

[James_Ball]

You could try p-Terphenyl-d14 as an Internal Standard.

Also check out EPA Method 8270 for doing PAHs by GC/MS.

http://www.epa.gov/waste/hazard/testmet ... /8270d.pdf