Sampling and GC-FID, GC/MS analysis of petroleum hydrocarbons in the ocean surface microlayer off Richards Bay, South Africa

Abstract In view of the demonstrated concentration of hydrophobic pollutants at the air/water interface and their expected deleterious effects on the associated neuston, surface microlayer sampling with a Teflon disc was introduced as part of a coastal oil pollution survey. Differentiation of the petroleum assemblages comprising the samples is demonstrated, using gas chromatography with flame-ionization detection and GC/MS with computer-reconstructed mass fragmentograms. The former technique provides parameters such as the carbon-number preference index, which distinguishes biogenic from petrogenic n-alkanes, whilst the relative abundances of ions characteristic of steranes and triterpanes indicate similarities among samples, and give further evidence of the petrogenic origin of the hydrocarbon assemblages found. Levels of petroleum hydrocarbons found are uniformly higher (expressed as μg/m 2 ) than those reported previously, where sampling techniques differed from the present one in taking a finite volume of surface water for analysis.