PCB analysis GC/MS

[Ruben]

I am new to GC/MS analysis, and am looking at quantifying PCBs(Arochlor 1254 and Arochlor 1260). Can some-one please help me with interpreting PCB data. I am using a Varian saturn 2000 MS coupled to a 3400GC.

Any advice and information would be appreciated.

Thank you.

[Don_Hilton]

Ruben,

Can you be more specific about what you want to know? Using GC/MS you can cofirm the identity of and quantify individual PCB's. The Arochlors are various mixtures of PCB's - and by knowing something about specific PCB's in the mix, you can say something about the mixture that was probably present in an environmental sample.

[Ruben]

Hi Don,

I would like to know how you quantify PCBs using technical mixes such as Arochlor 1254 and Arochlor 1260. I was told that one groups together certain peaks and quantifies them as PCBs. In theory is seems simple, but when I tried my results were inaccurrate, as I ran a verification standard to confirm and the concnetration was different. This may sound silly but would you mind running me through the quantification and interpretation process for PCBs. If you require my e-mail address I would be happy to provide that as well.


Thanks

Ruben

[Don_Hilton]

Ruben,

Since I don't know what kind of sample prep you have used, how you built your curve, what you are using for (or if you are using) an interal standard, or a number of other critical details, it is hard to figure out where to start.

Do you have a published procedure for this or are you trying to put something together on your own?

Did your verification standard have certified concentrations for any of the individual PCB's? And, did your calibration standard involve any individual PCB's? (My first thought here is to see if things were working well for individual PCB's - if not, then we need to look further back.)

Don

[Ruben]

Hi Don,

Samples are extracted with dichloromethane or hexane. I have tried using florisil SPE to cleanup the sample, but have achiewved poor recoveries. In short, I do not have a good method, and am trying to put together one. I have run the EPA 525 standard for individual PCBs and they all calibrated fine.

Any advice, methods etc. would be welcome.

Thanks

Ruben

[Don_Hilton]

If you are getting poor recoveries of the individual PCB's, the next question is what is your matrix? And if it is environmental, have you looked at the EPA methods for sample prep?

[Ruben]

The matrix is sediment and mussel tissue. I have extracted the samples using microwave digestion(1:1 hexane acetone). Concnentrated the samples to about 1ml and "cleaned" using florisil SPE cartridges. I ahve tried looking at the EPA methods but we do not have an ASE or soxhlet system. I am trying to adapt the methods to the equipment we have.

Can you recommend settings for the GC/MS, and/or a simple extraction method in these matrices?

Thanks

[Don_Hilton]

I can give you a couple of leads toward GC conditions.

Look for work by Eric Reiner (Ontario Ministry of the Environment) and his associates. (http://ijc.org:8080/glro/glro-web/prior ... ments/bha3) Reiner has been looking at PCB's in fish. The reference I posted uses ECD, but if look for other work by Reiner or some of the work by Don Patterson and Wayman Turner at CDC you should find some help in setting up mass spec conditions. While the CDC work may be helpful in setting up GC conditions CDC uses high resolution mass spec to get past interferences - but they are looking for levels in matricies like human blood serum.

That's about as far as I can take you... Perhaps someone else will jump in.

[carras]

Hi Ruben!

I analyze PCBs in oils and animal fat using GC/MS (single quadrupole), though only individual congeners (e.g. PCB 153), not mixtures like Arochlors .I have tried everything for sample clean-up (treatment with sulfuric acid and permanganate, Florisil, LLE…). The only thing that really works for me is GPC, and even then, things can get messy with the smaller congeners ( PCB28 in my case) due to interferences. I use the EPA Method 3640A with Envirogel columns from Waters, which speed up considerably the clean up. Caveat emptor, the columns are "expensive" and you’ll need a fraction collector (an autosampler would be very desirable too).

In my case matrix-matched calibration is a must and I strongly suggest you give it a try even if you decide against GPC.

[AICMM]

Ruben,

Regarding groups, typically, you run the Arochlor, you pick 5 peaks, you calibrate those peaks and then you group them together. When you run a sample, they should all, more or less, come back to you with the same concentration if it is a pure Arochlor. We used to throw out one or two if they were way out of whack but in general they will come back pretty similar.

Regarding cleanup, the acid method is very good although I probably would not use acetone in the extraction, just hexane, if I were going that route. I would also not use Florisil SPE but, instead, buy your own and make micro-columns using Pasteur pipettes. I used to do this all the time for PCBs in transformer oils.

I agree with carras that GPC will certainly do the job but it does require a lot more solvent. If you are on a budget I can tell you how to build one for yourself.

Regarding GC/MS, I would not think that a standard EI source would do very well with PCBs (as contrasted with negative ionization source) so I am wondering how low you want to go and how low others have gone.

Best regards.

[gpronger]

There is an option to simplify the quantitation, but will increase work on the prep side: perchlorination. This is a technique where we convert all PCBs present to a single peak (decachlorobiphenyl). You could then set up a SIM technique to gain sensitivity (given you now have only a handful of ions to monitor). The one issue would be that you may need to also analyze the sample for biphenyl prior to perchlorination since any biphenyl present will also be converted to decachlorobiphenyl. EPA method 508a (this is a drinking water method) covers perchlorination. You would need to adopt the technique to your matrix.

Greg

[AICMM]

Ruben,

As gpronger notes, perhchlorination will make quantification easier and give you a lower detection limit. The disadvantage is that you lose structural information so you won't be able to separate planar isomers from others for example.

Best regards.

[kerri]

Ruben-

I have a method developed (on the Saturn 2000) for PCB Arochlor mixtures. If you still need one, I can get the details when I get back to the lab on Wednesday. Its not the most perfect method (I used it for a teaching lab), but you could certainly tweek the temp ramps to fully resolve all of the peaks. The method works flawlessly for all the PAHs and PCBs singly.

What I can remember off the top of my head is that I used a Varian FactorFour VF5-ms column for the analysis. As for the quantitation, you most certainly would need to order single samples of the pcbs you are interested in and run a a calibration curve with an internal standard. This is really the only way to be sure of the measured concentrations.

Kerri

[Ruben]

Hi everyone, thank you for the feedback regarding my problem. It is appreciated. Kerri I would appreciate it if you could forward me the method you have, as I am also using a Saturn 2000 ion trap system for analysis. I am hoping that you have extraction methods as well. My sample matrix is sediment.Budget constraints make-it difficult to do GPC, and I am not too keen on the perchlorination method.

Thanks

[kerri]

Ruben-

Here is the method my class used for aroclor 1260 on the Saturn 2000:

Constant Flow = on
Injector Temp = 260
Split = 10

Temp program:
100 - 2 min hold
160 - 15/min ramp - 1 min hold
225 - 5/min - 0 hold

The m/z range for detection was 50-400

I attempted to find the actual chromatograms used with this method, but had no luck (apparently the computer harddrive had been replaced since). But the method could probably use a little tweeking with the temp ramps and such to accommodate the m/z range you prefer.


Cheers!