Rapid analysis using inactivated fused silica tube (a.k.a. “guard column”) as a sample inlet (2)

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. In MS Tips No. 111, the details of the “blank tube inlet / FI” method was discussed. In this application note, crude oil, diesel fuel, and kerosene were analyzed by blank tube inlet / FI, capillary GC/FI, and FD and the results were compared and discussed.