About this document
This technical report has been prepared to review the available information on the presence of polar metabolite compounds in samples collected from weathered petroleum hydrocarbon–impacted soil and groundwater. The aim is to identify an appropriate silica gel clean up (SGC) method for removing these compounds from the analysis of petroleum hydrocarbons, and to provide guidance on interpretation of the data collected, to ensure that risks to human health and the environment are adequately protected.
Analytical methodology for silica gel clean-up of soil and water extracts is proposed in this report. The methodology follows closely with NEPM Schedule B3 (NEPC, 1999 amended 2013c), that is analysis of semi-volatile hydrocarbons (TRH >C10 to C40) using solvent extraction followed by determination by gas chromatography–flame ionisation detector (GC-FID). The NEPM describes an optional SGC procedure but more detail is required. Appendix C details two procedures for SGC which are in common use in environmental testing laboratories – in situ and ex situ. These procedures have been adapted from CCME 2001, Reference Method for the Canada-Wide Standard for Petroleum Hydrocarbons in Soil – Tier 1 Method, and Addendum 1. The in-situ method involves adding silica to the extract to form a ‘slurry’. This silica then interacts and absorbs polar analytes. In the ex-situ method, the extract is applied to a silica gel glass column which removes polars from the extract. The extracts are then analysed by GC-FID. Advantages and disadvantages of both techniques are discussed in this report.