Calibration Table for PCB

[therdem]

Hi, I am confused on PCb analysis
Both PCB 30 and PCB 209 are internal standart for PCB analysis.
I have prepared solutions of 0 to 100 ppb(5 level) of PCB mix calibration solution that already have PCB 209
I have add PCB 30 to all five levels so that final consantration of PCB 30 is 25 ppb in all level.

How do I create a calibration curve on ınstrument? I mean I know how to do it. But I don't understand the logic here. On the instrument there are two old method, one of them PCB30 is selected as ınternal standart, in the other PCB209 is selected as internal standart.

Which one is correct or why I don't choose both of them as internal. There is also a option of reference next to internal. Is it something I have to choose.

[Steve Reimer]

Either one of them could be correct, depending on what you are doing. If you want to use both as internal standards then you split the target PCBs so that the early eluters (up through tetra chloro) use pcb 30 and everything later uses 209.

Note that if your sample has Aroclor 1268 in it there will be extra 209.