Robert B. (Chip) Cody is Principal Scientist at JEOL USA, Inc. He developed the trapped-ion tandem-in-time MS/MS and MSn techniques, laser-desorption in a trapped ion mass spectrometer, Electron Impact Excitation of Ions from Organics (EIEIO) and is coinventor of the DART ion source. Dr. Cody consulted with NASA on the Mars 2020 Rover project, served as Vice-President for Arrangements for the American Society of Mass Spectrometry and was awarded the 2011 Anachem Award and a 2012 Purdue University Distinguished Alumni Award. He is also responsible for the Mass Mountaineer software suite for mass spectral data analysis and reporting.
Gas chromatography combined with mass spectrometry is widely used for petrochemical analysis. In our laboratory, we use comprehensive two-dimensional gas chromatography (GCxGC), high-resolution mass spectrometry, and soft ionization methods (e.g. field ionization) for petrochemical analysis.
However, no single chemical analysis method is universal. Complementary techniques can reveal information that may be missed by traditional methods. While Direct Analysis in Real Time (DART) mass spectrometry does not offer the separation capabilities of GC-MS, the method is extremely fast, does not require sample preparation, and DART can often detect compounds that are not amenable to GC-MS analysis. Positive and negative-ion DART provide complementary information. Positive-ion DART mass spectra are generally dominated by additives, while negative-ion DART can provide a fingerprint of the base oil composition, including large saturated hydrocarbons detected as oxygen anion adducts.
A recent example involved aged, oxidized diesel fuel. A 1-year-old diesel sample stored at room temperature exhibited clear visual differences (discoloration and cloudiness) from a fresh sample from the same source. GCxGC-MS did not reveal any differences between the samples, but negative-ion DART showed distinctly different mass spectra. Additional examples to be presented include a DART MS study of motor oil degradation over time and observation of distinctive differences in DART mass spectra for biomarkers in crude oils from different geographic origins.