Application of Pearson Correlation Coefficient to Two-Dimensional Gas Chromatography High-Resolution Time-of-Flight Mass Spectrometry as a Comparison and Discovery-Based Technique

Vacuum gas oils (VGOs) have long been heralded as an effective plasticizer due to their high boiling-points and lubricating properties. One of these VGOs, HyVac® Oil 93050, is a paraffinic plasticizer that is currently utilized in many plastic-bonded explosive formulations, and while this oil is ideal in terms of increasing the elasticity and decreasing the sensitivity for current formulations, a list of potential VGOs with a similar density, viscosity, molecular composition, and impurities would be invaluable for future formulations. In this study, 18 VGOs, including HyVac® Oil 93050, were initially evaluated for density and viscosity. The oils were then ranked based on physical characteristics and analyzed for molecular composition using high-temperature comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry (HT-GC×GC-HRMS). Furthermore, because the datasets for the chromatograms being analyzed were large and complex, a simple metric was preferred when determining the similarities and differences between samples. This single metric concept led to the application of Pearson correlation coefficient. While Pearson correlation coefficient is well-known as a comparison technique, this study also utilizes it as a discovery-based method to determine significant chemical differences. Measurements of the covariances across the chromatograms utilizing the Pearson correlation coefficient equation were calculated, and visual representations of these differences were developed.