Analytische Chemie
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- Laser induziertes Plasma (1) (entfernen)
Only a few years after the invention of the laser, the concept of laser microprobe mass spectrometry (LMMS), a technique which employed intense laser radiation for ion generation, was introduced. In these early studies at excessive irradiation microplasma formation could be observed to be an effective channel for ion formation. However, this plasma generation in vacuum led to undesired distortions of the mass analyzers and, thus, was discarded as an analytical ion source.
Under ambient conditions, the surrounding air effectively cools the plasma cloud, making the plasma more controllable. The resulting laser induced plasma is nowadays commonly used in laser induced breakdown spectroscopy (LIBS) applications as excitation source for optical emission spectroscopy experiments. However, little effort has been made to introduce a LIBS plasma as a promising ion source for ambient mass spectrometry. The main hindrance is the transient character of laser induced plasmas that typically only has a lifetime on the order of several microseconds. This drastically reduces the duty cycle of these plasma sources. After these microseconds, the generated ions recombinate to uncharged
atoms and even newly bound molecules, making them inaccessible to mass-to-charge analyzers. The advent of high repetition lasers together with the ever growing knowledge about manipulation of charged species at atmospheric pressures allow overcoming these obstacles. This presentation will introduce an ionization scheme using a laser induced plasma as the primary ion source. We believe that this novel ionization strategy will pave the way for future applications in ambient mass spectrometry.