IMM Instrument Guides
IMM Instrument Guides
General recommendations for sample preparation for GC and GC-MS analyses.
All samples must be reasonable volatile. Otherwise they will just pollute the system and give no outcome.
In all cases, use solvents compatible with the GC column used in the system.[1] Choose solvents which has low vapor volume and low heat of evaporation. Otherwise, you can obtain split peaks, or unusual peak shape. Stay away of acids and bases (even as a co-solvents). They damage the column through desilylation quite fast. If you use protic solvents, analytes can get bound through hydrogen bonds impairing the analysis.
Hexane, heptane, pentane - good evaporation, low vapor volume.
Dichloromethane - only for CG-MS, good evaporation, reasonable vapor volume.
Diethyl ether - good evaporation, low vapor volume.
Dichloromethane:Methanol mixture - only for GC-MS, good evaporation when low amounts of methanol are used.
Dichloromethane:Isopropyl alcohol mixture - Only for GC-MS, good evaporation when low amounts of isopropanol are used.
Isopropyl alcohol - high heat of evaporation, viscous - unreliable splitting.
Methanol - high heat of evaporation, high vapor volume.
Acids - bleeds the column, even as a co-solvents
Bases - bleeds the column, even as a co-solvents
Water - very high heat of evaporation, very high vapor volume
halogenated compounds - applies only for GC-FID - they damage the FID detector.
Generally, it is good to start with 1 mg/ml of sample 1 μl injection and split 50. Peak shape determines how you should optimize the splitting ratio. Column capacity is roughly 5-700 ng/injection/component.