Real-Time Measurements of Polychlorinated Biphenyls Using Laser Ionization Time-of-Flight Mass Spectrometry

Polychlorinated biphenyls (PCBs) are hazardous compounds for which there are few methods involving real-time measurement. Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS (laser ionization time of flight mass spectrometry) technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the context of developing a highly selective and sensitive technique, the effective laser wavelength and pulse duration for laser ionization of 2 - 4 chlorinated PCBs are considered. Excitation at λ = 266 nm was found to be substantially more effective than at λ = 280, 300 or 320 nm. Also, picosecond excitation for PCBs underwent more efficient ionization (by a factor of over 10) and less fragmentation than nanosecond excitation. The achievable sensitivity for trichlorinated biphenyl in a real-time (1 min) measurement using the LI-TOFMS technique was estimated to be in the sub-ppbV range (< 0.01 mg/Nm3).