This document describes an automated clean-up method for mineral oil (or hydrocarbon oil index) analysis using the Agilent 7696A Sample Prep WorkBench system. Using this method, drying and clean-up of samples obtained after liquid-liquid extraction can be automated. High recoveries and excellent reproducibility are obtained for the mineral oil fraction, while the clean-up step is very efficient. The extracts are analysed by GC-FID. In combination with low thermal mass (LTM) – GC, an automated high throughput method is obtained.
The document details an environmental analysis method for determining hydrocarbon oil index (HOI) or total petroleum hydrocarbons in water samples. It focuses on automating the sample preparation steps, specifically drying over sodium sulphate and cleaning up using Florisil adsorbent, which are performed after liquid-liquid extraction.
The Florisil adsorbent is used to remove more polar, co-extracted solutes such as lipids from the sample extract.
The Florisil adsorbent must be heated at 140 °C overnight to remove residual water before use.
An amount of 30 mg (+ 2 mg) of Florisil is considered a safe margin for the clean-up procedure.