Multiphoton ionization/mass spectrometry of polybrominated diphenyl ethers

Gas chromatography combined with multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) using ultraviolet picosecond and femtosecond lasers was employed to quantitatively analyze a series of polybrominated diphenyl ethers (PBDEs). Congeners from monoBDE to tetraBDEs were analyzed using a picosecond laser emitting at 266 nm. In order to enhance the efficiency of ionization for highly brominated DEs via triplet levels, a different laser emitting at 213 nm was used. It was, however, difficult to quantify such congeners, even at this wavelength. This unexpected result can be explained by the photodecomposition of PBDEs from the triplet levels. On the other hand, all congeners from monoBDE to decaBDE were detected when a femtosecond laser emitting at 267 nm was employed. Interestingly, the isomers having a smaller number of Br atoms at the meta-positions were more efficiently ionized, and provided lower values of detection limit.