Rapid analysis using inactivated fused silica tube (a.k.a. “guard column”) as a sample inlet (1) [GC-TOFMS Application]

Average molecular weight is an important reference for evaluating samples with molecular weight distributions, such as crude oils, which are complex mixtures, or synthetic polymers. Almost all the ions observed in field desorption (FD) and field ionization (FI) mass spectra are molecular ions since these are soft ionization methods. Average molecular weight of the sample can be calculated directly from the masses (or “m/z”) and intensities of all ions observed by FD or FI. By applying group-type analysis, the components can be classified into types based on their functional groups and/or unsaturations. Average molecular weight, polydispersity index, or relative abundance of each type can be obtained. A diesel fuel was analyzed on JMS-T100GC “AccuTOF™ GC” with 3 sample introduction methods and the results were compared:

• Capillary GC / FI
• Rapid FD in which the analysis time was shorten by ramping the emitter current much faster than that on conventional analyses on double-focusing mass spectrometers
• Blank tube inlet / FI in which a fused silica tube was used to connect the GC injector and the ion source