PCB analysis via 6 compds

[thohry]

Hi all,

In a method for PCB analysis, it says you only have to analyze 6 PCBs: 28, 52, 101, 138, 153 and PCB 180. Then, the total PCB concentration can be derived from the total of only six PCBs. There are many more congeners, and there are some more toxic. I am rather puzzled about this.
Could anyone help ?

Thanks for any inputs.

[Yama001]

There is a low res Mass Spec method 680 (and a high res as well -1622 perhaps?) that does something like this. A conjener from each chlorination level is used for calibration. Any peaks within an established retention time range for each chlorination level are identified by checking the M and M+2 mass ratios. All qualifying peaks are summed up for a total PCB number. It uses the known isotope ratios of Chlorine 35 and 37 for identification criteria.

Data analysis is a bit of a pain - I use a routine I wrote years ago to identify the peaks and sum them up. It works well - I get 95 to 100 percent accuracy when I quant a conventional arochlor mix. It can be a useful check against ECD based methods. Also nice for samples where the Arochlor is weathered. Both approaches are diminished by interfering compounds. I assume the high res MS method has less problems here.

[thohry]

Thanks Yama, your explanation is helpful.
I use GC/ECD for transformer oil samples.