1. ISOF, Consiglio Nazionale delle Ricerche Via P. Gobetti 101, 40129 Bologna, Italy, Department of Chemistry and Biochemistry, Ludwig-Maximilians University Munich, 81377 Munich, Germany, MS and Dioxin Analysis Laboratory, IRRP, National Centre for Scientific Research ‘Demokritos', Athens 153 10, Greece, and Department of Chemistry, University of Athens, Panepistimiopolis, 15771 Athens, Greece