Determination of organochlorine compounds in neuston from the Mediterranean

A reliable analytical procedure was developed to determine trace levels of organochlorine compounds in neuston samples. Freeze-dried samples were extracted by sonication (3 x 15 ml cyclohexane, 15 min) followed by gel permeation chromatography (GPC) and gas chromatography electron capture detection (GC-ECD) determination. Neuston samples may present great differences in their lipid content, which may become a drawback for the analytical determination of hydrophobic pollutants. In this way, GPC fractionation combined with Florisil cleanup was successfully used to avoid potential lipidic interferences in the GC-ECD determination. Organochlorine compounds were determined by GC-ECD and a standard addition method was performed to evaluate the recoveries of 41 PCB individual congeners (80 +/- 20%). The congeners with lower K(ow) (octanal water partition coeeficient) values showed lower recoveries (54 +/- 7%) than the more lipophylic ones (80 +/- 7%). The limits of detection ranged from 0.001 to 0.211 ng g(-1) of wet samples. The reproducibility of the developed analytical methodology for independent replicates (n = 3) at low pg g(-1) levels was quite satisfactory (RSD 18 +/- 10%).