Analytical Instrument Documents

Comprehensive 2-dimensional GC (GC x GC) provides higher-separation capabilities for complex mixtures than the typical 1-dimensional GC measurements. However, this technique requires high speed data acquisition, e. g. > 20 Hz, for the GC detectors due to the shorter 2nd GC column (comparable to those used for the ultra-fast GC measurements) which elutes samples within just a few seconds. Recently, JEOL has developed a new generation GC-HRTOFMS system called the “AccuTOF GCv 4G”. The AccuTOF GCv 4G has high sensitivity, high resolution, high mass accuracy and high speed data acquisition, all simultaneously. Also JEOL has developed a unique EI/FI combination ion source for this system which provides the capabilities of GC/EI and GC/FI measurements without having to break vacuum in order to switch between each ionization mode. Additionally, this combination is particularly powerful in that it provides library searchable fragmentation information by using EI and high mass accuracy molecular ion information by using FI.

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.

Comprehensive two-dimensional gas chromatography (GC x GC) in combination with high-resolution mass spectrometry is a powerful tool for the analysis of complex mixtures. In this work, we analyzed a diesel fuel sample by using GC x GC in combination with a new high-resolution time-of-flight mass spectrometer (HR-TOFMS) . Field ionization (FI) produced molecular ions for all components and exact mass measurements were used to obtain elemental compositions. A traditional Kendrick Mass Defect (KMD) plot was used to identify hydrocarbon groups in the diesel fuel sample.

Electron ionization (EI) is a common ionization technique for gas chromatography/mass spectrometry (GC/MS). However, EI often does not produce strong molecular ions (M+・) because the excess energy generates fragment ions during the ionization process. The detection of the molecular ion is very important for confirming the molecular weight of the target compounds. Therefore, a soft ionization technique is often necessary to determine the molecular weight information. Field ionization (FI) is well known as one of the softest ionization techniques commercially available. Similarly, photoionization (PI) can produce molecular ions. In this application note, the characteristics of PI and FI were investigated by using various compounds. Furthermore, the performance between EI, FI and PI for these compounds in diesel fuel were investigated.

Comprehensive two-dimensional gas chromatography (GC×GC) is a kind of continuous heart-cut GC system. Two different types of columns are connected via a modulator in the same GC oven. By using the two columns together, this technique provides very high separation capabilities when compared to one- dimensional GC analysis. This report shows the difference of separation result for diesel oil when 2 different sets of combined columns are used with GC×GC-HRTOFMS (FI).