|From clear liquids to clear solutions!
|Ion Mobility - Mass Spectrometry (BMSS)
|Mr Alex Ttofi
|Dr Wicking Chrissie
Dr Whitmarsh Sam
Mr Sam Ellick
Mr Vincent Basham
Abstract Information :
The major component of a formulated lubricant is a carefully selected mixture of base oils. These raw materials are classified into 5 groups, primarily based upon the amount of refining required to produce them. New types of base oil have recently emerged within the industry such as gas-to-liquids (GTL) that perform differently to traditional base oil types but can be hard to distinguish from other highly refined mineral oils.
Initially a project was set up to automatically distinguish GTL from group III base oils in fully formulated oils. This was further expanded to include other base oil groups with a brief to simplify and automate the process of base oil identification. Many neat base oils of all groups were run by Field Desorption to provide base oil group trends against which unknown samples could be compared. The technique allowed for identification of the different base oil types and was chosen from others available, but using current technologies, was labour intensive and difficult to automate.
Field ionisation mass spectrometry (FIMS) was then selected as an alternative. The soft ionisation technique enables analysis of hydrocarbons with little to no fragmentation allowing the molecular formula of intact hydrocarbons to be determined. This coupled with a high resolution time of flight (TOF) mass spectrometer allows more specific classification and identification than ever before. A library of pure base oils was developed to establish reference patterns. This allowed unknown formulated products to be characterised using the carbon number & double bond equivalents even if they were found to be mixtures of different groups.
This analysis could be automated and samples run in just a few minutes with a data processing time of 10 minutes. There is also no need to perform time consuming sample preparation steps to filter out the polar additive molecules saving time and resources. Base oil analysis using FIMS is not a new development. Applications in the literature Include crude oils, distillate molecular weight predictions and base oils. Our novel challenge has been to apply such named chromatographic techniques to measure and identify GTL & base oil groupings in fully formulated products & develop reference libraries & data processing strategies that allow for automated processing of the data for unknown samples.
Looking to the future there are many application areas where the rapid identification of hydrocarbon mixtures may assist in process optimisation and complex material characterisation.