Gas Chromatography/Femtosecond Multiphoton Ionization/Time-of-Flight Mass Spectrometry of Dioxins

摘要

Gas chromatography/multiphoton ionization/time-of-flightnmass spectrometry (GC/MPI/TOF-MS) was developed forntrace analysis of polychlorinated dibenzo-p-dioxins andnpolychlorinated dibenzofurans (PCDD/Fs). The use of annultraviolet femtosecond laser (266 nm) allowed the sensitive,nas well as selective, determination of PCDD/Fs withnshort singlet-excited-state lifetimes; the detection limit wasn19 fg for 1,3,6,8-tetraCDF. Performance of the analyticalninstrument was examined and was ascertained to bensatisfactory for all the criteria (K0311) prescribed by thenJapanese Industrial Standards (JIS). The relative ionizationnefficiencies of 12C-native PCDD/Fs against 13ClabelednPCDD/Fs were 1.002 ( 0.012. This suggestsnthat 13C-labeled isotopes can be used as internalnstandards with no intensity calibration and that thenconcentrations of PCDD/Fs can be determined tonwithin an error of ca. 1%. In addition, multiphotonnionization provides negligible levels of backgroundninterference for the real soil samples even with curtailednpretreatment. The toxicity equivalence (TEQ) ofnthe real sample was determined using GC/MPI/TOFMSnfor performance evaluation against high-resolutionngas chromatography/high-resolution mass spectrometryn(HRGC/HRMS). The results suggest equivalent orneven superior performance for GC/MPI/TOF-MS, duento low background interference and to the ability toncheck the reliability of the assignment from the intensityndistribution of the isotope peaks.