Volatiles

[Joaquin]

I am quantifying nonadienal and some other aldehydes, now that I was able to get peaks with my standards I have problems with my samples. Probably my sample contains very little of these aldehydes that the headspace sampler cannot detect them --there may be other factors.

My heaspace parameters are as follows: 5 g ground meat sample in a 22ml vial heated at 60C for 60 min, 0.2min injection volume, 0 min pressurization time, 65C needle temp, 130c transfer line. My GC parameters are FID:280C, injector:250C, oven 40C for 5min, and 10C/min to 240C. Split 1:1 at 10 psi helium carrier.

I hope you share some insights on how should i improve the sensitivity of my analysis. Thanks once again.

[Radish]

I would try SPME for this analysis.

[chromatographer1]

Aldehydes are very reactive and your extended heating choice would not be mine.

I think SPME is an excellent idea and should work well. I would allow the sample to sit at 35°C or less for 10-30 minutes before sampling for an additional length of time with the SMPE fiber.

Good luck.

Rod

[Joaquin]

Thank you guys, do you think i have no other options besides SPME? What kind of SPME should I use?

[adam]

It's been a long time since I did headspace analysis, so I can't help with respect to suggestions about your headspace program. Regarding the GC program: are you sure you are focussing the analytes sufficiently. I don't know if 40C and a 1:1 split would do the trick for really volatile analytes. I would think you would need a lower starting temperature or a larger split ratio, to see good peak shapes.

Also, I think I would disagree with the suggestion to use SPME. If you are dealing with very volatile analytes, headspace should be more sensitive than SPME.

Hope this is of some help. Adam

[chromatographer1]

When properly done, SPME can measure orders of magnitude lower than headspace, and I was able to perform headspace looking less than 1ppm of impurity in a 1mg (<1ng) sample for dozens of volatiles in my published paper almost a decade ago. I also developed a benzene analysis in waste water using an FID at levels of less than 100ppt using static headspace analysis so I think my opinion has merit.

SPME can go MUCH lower than this albeit with a somewhat higher RSD (several percent.).

Proper technique is needed for both types of analyses but both can be the proper tool given the proper analysis.

best wishes,

Rod

[chromatographer1]

Joaquin,

I would call or email Supelco technical service for assistance in choosing the proper fiber for SPME.

techservice@sial.com

[Joaquin]

Thank you adam and rod, i will consider your suggestions.