Development and validation of sample clean-up using solid phase extraction prior oil spill fingerprinting

Abstract: In a forensic investigation involving oil, a comparative analysis named oil spill fingerprinting between a source and an oil spill is normally performed. It is based on detecting a certain selection of biomarkers with gas chromatography (GC) coupled to mass spectrometry (MS) which are later divided into diagnostic ratios (DRs). An international guideline formed by European Committee for Standardization (CEN) denoted CEN/TR 15522-2:2012 describes the process of conducting oil spill fingerprinting. This method is currently being inspected and adjusted for standardization into EN 15522-2:2022. One section of the upcoming standard describes sample clean-up which is important to inhibit possible matrix effect that could either enhance or reduce peak intensity in the chromatogram. There is yet no conclusive SPE (Solid Phase Extraction) protocol in the current draft version of EN 15522-2:2022. The aim with this study was to develop such a protocol. Development included comparative testing of the recommended stationary phases silica and Florisil®. Additionally, the effect of both elution solvent and elution volume were investigated. The protocol must pass validation criteria to be implemented at National Forensic Centre (NFC) and possibly be used in the final version of EN 15522-2:2022. A successful method for Heavy Fuel Oil (HFO), diesel and lubricating oil was achieved with activated Florisil® as stationary phase, eluted with 6 ml dichloromethane (DCM). If the evidence material is suspected to contain FAMEs (Fatty Acid Methyl Esters), then 2 % acetone should be added to the DCM. The final SPE column was packed with 0.5 glass wool, 4 cm Florisil® and 0.5 cm sodium sulfate. Based on successful validation result, the SPE protocol should be considered for the final version of EN 15522-2:2022 as well as for implementation at NFC.