GCxGC TOFMS Analysis of Base Oils with CI, PI, FI
Introduction
Structural elucidation of hydrocarbon classes in petroleum products are always in high demand. Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) with electron ionization (EI) is a powerful method for characterizing complex mixtures such as base oils. However, EI data can often lack a strong molecular ion signal. Therefore, it is necessary to measure samples with soft-ionization methods such as positive chemical ionization (PCI), field ionization (FI), or photo-ionization (PI) for the detection of molecular ions. Each technique is a little different so it is important to understand the characteristics of each soft ionization method.
In this application note, we compare the mass spectra of a base oil analyzed by GCxGC-TOFMS with EI, PCI, FI, and PI.
Experiment
The details for sample dilution in hexane as well as the instrumental conditions are listed in Table 1.