I need to compare two products of same brand by GC / GCMS, i have tried to extract the volatile part of the aqueous beverage by using CH2Cl2, pentane:diethyl ether; but the volatile are very less.
please suggest me any good method of sample preparation.
Many Thanks
Selvan
Hi Selvan,
you can try purge and trap GC for determination of volatiles from liquides. It works very well and all you need is a coolable injektor at you GC/MS system.
thank lot for all, i have solved the problem with GCMS-SPME
Selvan
Head-space analysis is the way forward. You can gently warm the sample in a glass vial, with a septum, and inject the headspace above to a conventional GC.
We are moving away from Purge and Trap towards SPME. We use headspace vials with the Gerstel MPS II autosamplers on orange juice. SPME does have issues however. There can be issues with very abundant compounds crowding out trace analytes due to the fibers's limited capacity, There are two complicated equilibria (liquid to heaspace and head space to SPME) that are affected by any matrix changes. For instance addition of any organic solvent (other than single carbon like methanol or ClxCx will depress analyzes by crowding them out on the fiber.
Overall I'd say it is the wave of the future though twister is also up and coming thoug currently only PDMS is available. I use carbonx and DVB PDMS for SPME.
Use SPME-GC/GC-MS. PDMS-SPME fibres from SUPELCO. For better result In GC or GC-MS you must go with Splitless mode. This will give you best results. I have done this in case of tea flavour.
If you are doing liquid-liquid extraction, splitless mode will give you best results. Because in case of Split mode you will not get minor volatile flavour components and will miss you exact aroma profile.
:)
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