Evaluation of Raman shifter in resonance-enhanced multiphoton ionization time-of-flight mass spectrometer.

摘要

Resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI TOFMS) is advantageous for isomer-selective identification due to its high selectivity, high sensitivity and rapidity. This work aimed to develop an infrared-selective 1+1+1 REMPI TOFMS to distinguish the isomers of polychlorinated aromatics. In the initial phase, it was the first time that a Raman shifter was employed to generate UV beam for the light source of REMPI. The instrumental parameters such as carrier gas pressure, the pulsed valve current and delay time between valve opening and laser firing were investigated to maximize the peak intensity of m/z 92 of toluene. Time-of-flight mass analyzer was studied in terms of the peak intensity and mass resolution of m/z 92. The active gas in the Raman shifter was selected based on toluene ion signals. 1+1 REMPI of toluene was demonstrated. Further work would be focused on generating an infrared photon suitable for rovibrational pumping.