Comprehensive analytical methodology to determine hydrocarbons in marine waters using extraction disks coupled to glass fiber filters and compound-specific isotope analyses

•Analyses of dissolved and particulate hydrocarbons (C18 disks and GFF filters).•Carbon isotope fingerprinting was explored to trace the source of oil pollution.•The method was applied to natural seawater samples.•Linear alkylbenzenes (LAB) were identified in the particulate phase of the seawater.

Solid-phase extraction of both aliphatic (AHs) and aromatic polycyclic hydrocarbons (PAHs) from seawater samples was evaluated using a GFF filter stacked upon an octadecyl bonded silica (C18) disk. Stable-isotope measurements were developed on hydrocarbons extracted from both GFF and C18-disks in order to characterize the source of hydrocarbons. A clear partition of hydrocarbon compounds between the dissolved and the particulate phase was highlighted. PAHs showed a higher affinity with the dissolved phase (recoveries efficiency of 48–71%) whereas AHs presented strong affinity with the particulate phase (up to 76% of extraction efficiency). Medium volumes of seawater samples were tested and no breakthrough was observed for a 5 L sample. Isotopic fractionation was investigated within all analytical steps but none was evidenced. This method has been applied to harbor seawater samples and very low AH and PAH concentrations were achieved. Due to the low concentration levels of hydrocarbons in the samples, the source of hydrocarbons was determined by molecular indices rather than isotopic measurements and a pyrolytic origin was evidenced. The aliphatic profile also revealed the presence of long-chain linear alkylbenzenes (LABs). The methodology presented here would better fit to polluted coastal environments affected by recent oil spills.