SPME/GC-MS analysis of lipid oxidation volatiles

[bucki]

I wanted to analyze headspace volatiles of fatty acid oxidation.
I prepared 400 ppm standard solution of pentanal in hexane; i am not sure what conc of std and solvent to use.
aAfter SPME/GC-MS run, I can't see pentanal peak; i am assuming hexanal is coeluting with hexane.
Can some one help me in choosing right conc and solvent for std preparation? GC/MS conditions are below.

75 µm CAR/PDMS
Column - CP-Sil8 CB low bleed/MS fused-silica capillary column (5% phenyl/95% PDMS; 60 m x 0.25 mm ID, 0.25 µm; varian chrom pack)
Start – Injection port – Splitless
Split flow – after 0.5 min
Injector Temp – 250C
40 C – hold 2 min; 40 to 120 C @ 4C/min; 120 to 250 C @ 20C/min; 250 C – hold 10 min
FID – 280C
Helium – 16 psig
Scan range m/z 29 to 400 @ 1.9 scan/sec
Ion source temp – 170 C
Emission current – 50 µA
Electron energy - 70 eV

Appreciate any help! Thanks before hand.

[Peter Apps]

From a purely chromatographic viewpoint the solvent has to be something that you cannot see with the detector (which pretty much limits it to water) or that elutes far enough away that the peak does not interfere with the analytes (even when present in huge excess).

From a broader perspective, since SPME is a selective partition method you have to prepare your standards in the same matrix as your samples.

Peter

[bucki]

Thanks very much. I prepared the standards in the same matrix as my samples. Now it works. Appreciate your suggestion.

Ramesh.

[Peter Apps]

Thanks for the feedback.

Peter