By wsb on Thursday, May 10, 2001 - 11:18 pm:
Dear Chromatographers!
we routinely are running typical PAHs on HP1100 with DAD after solid-phase extraction using Coronen as IS. We would like to change to an other IS-compound, since Coronen behaves different in SPE compared to the other PAH.
I would like to change to a derivated PAH-compound, but I heard of the even more toxic or carcinogenic character, so has anyone an idea which compound to use (relatively) save, which does not interfer with standard PAH in chromatographic analysis?
Thanx in advance
thomas
By bill tindall on Friday, May 11, 2001 - 07:01 pm:
what problem are you trying to fix with the internal standard? imprecision of injection, variable extraction?
By wsb on Sunday, May 13, 2001 - 10:48 pm:
High Bill,
the main problems we see are different behavior and low reproducibility of coronen during extraction in comparison with standard PAHs
thomas
By bill on Tuesday, May 15, 2001 - 07:59 pm:
you answered with the problem with coronen, but the information needed to pick an appropriate internal standard is.........what problem with the PAH's are you having that you need an internal standard. If the problem is poor precision of injection, than about anything will work, but a better fix would be a working injector. If the problem is the PAH's don't quantitatively extract, then you need something that extracts exactly like the PAH's of interest. Or whatever. The point is, the place you must start is to know why you need an internal standard. Then you pick one with the proper properties. Then, most importantly, you test to see that it is fixing the problem you are using it for. That is to say, you test to see that the data is better with the internal standard than without it.
If you haven't demonstrated a problem, such as inefficient extration or whatever, don't use an internal standard.
So, to ask again, what problem with the analysis do you want the internal standard to try to fix.
By H W Mueller on Wednesday, May 16, 2001 - 02:45 am:
See also "Quantitation of peaks in the 0.1-1% Range", ~Dec 6, 2000.
By wsb on Monday, May 21, 2001 - 10:39 pm:
High Bill,
the problem is poor recovery of PAH´s in aqueus samples of different matrix (drinking water - waste water).
Of course, we need an internal standard which behaves similar to our analytes - Coronen did not proof to be suited for it.
Any suggestions with respect to the toxicity?
thomas
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