Chromatography Forum

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.

I would try SPME for this analysis.

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

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

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

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

Joaquin,

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

techservice@sial.com

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