Chromatography Forum

I am doing research using SPME technique, and my sample's concentration is really low. Does Agilent 5973N Enhanced Turbo MSD with 6890N GC suitable for SPME? (We do not have enough money for the new one)?

It really depends on how low "really low" is. Certainly use SIM mode if you know what you're looking for.

It really depends on how low "really low" is. Certainly use SIM mode if you know what you're looking for.

I am doing Volatile organic compound from fungi sample, the concentration should be ppb or even lower.

I used a 5973N with SPDE (Not SPME) to detect and quantify volatiles at ppb and ppt levels. Of course, not all volatiles are equally doable at such low levels, but it's certainly not impossible with a 5973.

I used a 5973N with SPDE (Not SPME) to detect and quantify volatiles at ppb and ppt levels. Of course, not all volatiles are equally doable at such low levels, but it's certainly not impossible with a 5973.

Thanks! Have you ever used Agilent 5975 GC/MSD 7890? How much sensitive they are?

The 7890 GC won't really add sensitivity. It just cools down faster and has finer EPC control. The 5975C with Triple Axis should give better sensitivity but I haven't really seen the older 5975's to be that much more sensitive than the 5973's. pm me if you want to chat about SPME.

The 7890 GC won't really add sensitivity. It just cools down faster and has finer EPC control. The 5975C with Triple Axis should give better sensitivity but I haven't really seen the older 5975's to be that much more sensitive than the 5973's. pm me if you want to chat about SPME.

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Picking up from the duplicate thread ......

ppb concentrations with SPME are going to be difficult, especially if you have a range of compounds that you need to investigate because the fibres are selective (or biased depending on how you look at it) for particular classes of compound. Working in the ppb range with SPME I find that bleed and contaminants from the fibre are significant problems.

If I were you I would be looking at some variant of purge and trap, exactly which variant would depend on the aims of the investigation.

At the MS end of the column the critical question is whether you need to identify compounds from their mass spectra, in which case you need low limits of detection in full scan, or whethter you are looking for known target compounds, in which case you can go for SIM.

Peter

Picking up from the duplicate thread ......

ppb concentrations with SPME are going to be difficult, especially if you have a range of compounds that you need to investigate because the fibres are selective (or biased depending on how you look at it) for particular classes of compound. Working in the ppb range with SPME I find that bleed and contaminants from the fibre are significant problems.

If I were you I would be looking at some variant of purge and trap, exactly which variant would depend on the aims of the investigation.

At the MS end of the column the critical question is whether you need to identify compounds from their mass spectra, in which case you need low limits of detection in full scan, or whethter you are looking for known target compounds, in which case you can go for SIM.

Peter

Yes, you are right. Actually, I am doing something which is similar as what they did before(VOCs from fungi). But I am using different fungi, I have not gotten anything. Does inlet liner affect result a lot?

Yes, the inlet liner can make a big difference, you need to use the narrow bore liners specifically made for SPME.

There are a large number of other technical issues that need attention - which fibre, sampling temperatures and times, column phase and dimensions, desorption conditions etc etc.

VOCs at ppb levels does not tell us much about what you are trying to do, so it is difficult to give advice.

Peter