Relationship of moleculated radical anion abundance and calculated lowest unoccupied molecular orbital energies for polychlorinated dibenzofurans and dibenzodioxins in electron capture negative ion mass spectrometry: Evidence for negative metastable ions

Relationships were found between experimentally measured molecular radical anion abundances and calculated lowest unoccupied molecular orbital energies (ε LUMO ) for polychlorodibenzofurans and polychlorodibenzo‐ p ‐dioxins. Anion abundances were measured using standard using standard mass spectrometric techniques, while ε LUMO were calculated by the ‘Complete Neglect of Differential Overlap’ method. Polychlorodibenzofurans with calculated ε LUMO ≥ 1.6 eV show 0% molecular radical anion and those with ε LUMO ≤ 1.4 eV show ≥ 80% molecular radical anion abundance. Similarly, the molecular radical anion is absent for polychlorodibenzo‐ p ‐dioxins with calculated ε LUMO ≥ 2.0 eV. A trend towards greater molecular radical ion relative abundance appears for 2.0 eV ε LUMO ≥ 1.0 eV and a maximum is reached around 1 eV, whereupon the molecular ion abundance diminishes with lower ε LUMO . B/E linked scan analysis indicates that chlorodioxins with ε LUMO < 1 eV give increasing amounts of metastable anions.