An improved method for the recovery of petroleum hydrocarbons from fish muscle tissue

Abstract

A method based on fish muscle hydrolysis with NaOH followed by addition of CaCl 2, and steam distillation, with direct analysis of a dichloromethane extract of the distillate by capillary gas chromatography (GC), was evaluated for the recovery of bioaccumulated water-soluble hydrocarbons from high-fat salmon muscle with the objectives of combining simplicity and minimal contamination by other materials. The 17 hydrocarbons tested as model compounds were primarily aromatics in the benzene-methylnaphthalene range, including several substituted benzenes and naphthalenes but as well included some shorter chain aliphatic compounds. The mixture is representative of the major hydrocarbons present in the muscle of salmon which have been exposed to the seawater-soluble fraction of crude oil. Recovery studies were conducted at three concentration levels. The standard solutions were spiked into 20 g of homogenized salmon fillets and the mixture hydrolysed in NaOH solution for 2 h in a stoppered distillation flask. This was followed by the addition of CaCl 2 in solution to reduce foaming and 2 ml of dichloromethane as a co-distillation solvent. The mixture was then steam distilled with the dichloromethane recovered in the distillate as the hydrocarbon carrier. Such distillates contained negligible amounts of non-hydrocarbon material, and were therefore suitable for direct GC analysis without the need of any clean-up step. Recoveries for all hydrocarbons analyzed were high and reproducibility acceptable in the higher spiking levels. The major advantage of the method is a reduced background level of non-hydrocarbon volatiles from control salmon flesh. This increases the sensitivity of determining bioaccumulated tainting hydrocarbons while maintaining the basic simplicity of steam distillation.