Real-time measurement of polychlorinated biphenyls using laser ionization time of flight mass spectroscopy

Polychlorinated biphenyls (PCBs) are environmental chemicals and there are few methods for real-time PCB measurement. This study demonstrates the applicability of the real-time measurement of PCBs using LI-TOFMS (Laser Ionization Time of Flight Mass Spectroscopy). In order to develop a highly selective and sensitive method, the effective laser wavelength and pulse width for laser ionization of PCBs are discussed. Excitation at λ = 266 nm is found to be substantially more effective than at λ = 280, 300 or 320 nm. Also picosecond excitation for PCBs undergoes more efficient ionization (by a factor of over 10) and less fragmentation than nanosecond excitation. The achievable trichlorinated biphenyl sensitivity for real-time (1 min) measurement using the LI-TOFMS technique is determined to be in the sub-ppbV range (< 0.01 mg/Nm³).