Chromatography Forum

Hi Everyone,

I am working on setting up EPA method 600 for the analysis of PCBs in transformer oil and I am having trouble reporting my results. Right now we run a 7 pt calibration curve (quadradic) standard concentrations are 0.1, 0.2, 0.4, 1.0, 2.0, 3.0, and 4.0 ppm. This is the TOTAL PCB concentration in the sample vial, the problem I am running into is while calibrating, if I put these concentrations into my calibration table in Chemstation it reports that each peak I calibrate for has a concentration of X ppm when in fact the sum of all of the PCB peaks in the sample is X ppm. I was hoping someone could provide some insight as to how to report this, or how to split the total concentration among the 10 or so peaks that come through the GC.

Thanks in advance for the help!

You simply need to know the concentration of the individual PCB's, or you can't do a proper calibration.

Usually these are bought in a mix, with the same concentration for each PCB. You should have a certificate of the supplier, listing the exact individual concentration.

In OpenLAB 2 andere OpenLAB EZChrom you can create a calibration curve for a group so Total PCB. Van you not do that with ChemStation?????

We never used the GC Chemstation for our GCs but the MSDChemstation works great for this type of work. Set compound type to L and it allows you to sum the separate components to total of the individual peaks. There should be something like this in the GC Chemstation I would believe.

Normally if you get the standards as the Arochlors the individual peaks will all have different concentrations but the standard will be listed as the concentration of the total, similar to gasoline or diesel fuel standards are set at the total not the individual components. If the PCB is stated as an Arochlor concentration then you choose 5 representative peaks and give them all the same concentration equal to 1/5 of the total then sum the individual peaks, or you give all 5 the total concentration value and average the 5 peaks to report as the total. Both methods should work for the Arochlor.

If you have a mixture of known individual congeners then you will simply calculate each one as individual compounds.