Rapid Analysis Using Deactivated Fused Silica Tubing(a.k.a. “Guard Column”) as the 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 of the ions observed in field desorption (FD) and field ionization (FI) mass spectra are molecular ions since they are both soft ionization methods. The average molecular weight of a sample can be calculated directly from the masses (or “m/z”) and intensities of all of the 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 (Rapid analysis Part 1), the details of the “blank tube inlet / FI” method were 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.