Chromatography-mass spectrometry and toxicity evaluation of selected contaminants in seawater

in the present work a combined analytical study involving gas and liquid-chromatography and toxicity studies were developed for the determination of various contaminants typically present in sea water samples. The compounds investigated were Diuron, Chlorothalonil, Dichlofluanid, TCMTB (2-thiocyanomethylthiobenzothiazole), Irgarol 1051, Sea nine 211 and MTBE (methyl-tert-butyl ether). The selected compounds are additives of boat paints and gasoline and they can release into the aquatic environment in considerable amounts in areas with intense shipping traffic. The developed analytical protocol consisted on the use of a solid phase extraction procedure with Oasis(TM) HLB cartridges followed by GC-EI/NCI-MS and LC-ES-MS both in SIM mode. Average recoveries, loading 600 mL of samples with pH = 3, varied from 40 to 95% and the detection limits ranged from 1 - 25 ng L-1. The developed method was applied to real samples from various marinas of Andalusia (Spain). Dophnia magna, Vibrio, fischeri and Selenastrum capricornotum toxicity bioassays on individual and mixtures of selected compounds were applied to evaluate EC50 (effective concentration) and LOEC (lowest observable effect concentration) values. Resulting values were in the range of 0.001 - 720 mg L-1 for EC50 and 0.8.10(-9)-30 mg L-1 for LOEC for all contaminants except for MTBE where no toxic effect were found up to 680 mg L-1 on Dophnia magna. Toxicity effects of binary mixtures of the selected compound showed synergistic effects in the majority of the cases (4769/6) and antagonistic in the lower of the cases (9.5%). Levels of the contaminants found in the seawater samples showed around a 30% of inhibition on tested species, during the summer months considering mixture Irgarol 1051-Diuron. Accelerated toxicity processes were observed in mixtures MTBE-Diuron and MTBE-Dichlofluanid.