Femtosecond\nLaser Assisted Chemical Ionization Mass\nSpectrometry: Toward Sub-ppq Detection Limits for Organic Molecules

Ultrasensitive analysis of organic molecules is crucial\nfor various\nfundamental research and applications. State-of-the-art techniques\nfor this purpose can achieve detection limits of several hundred ppq\n(parts-per-quadrillion), while a higher sensitivity is pursued constantly.\nTo achieve this goal, we develop femtosecond laser assisted chemical\nionization for mass spectrometry. This technique combines the advantages\nof femtosecond laser ionization and chemical ionization, either of\nwhich enables subppt (parts-per-trillion) mass spectrometry analysis\nof organic molecules. The results demonstrate that the developed ionization\ntechnique, when employed in mass spectrometry, can surpass femtosecond\nlaser ionization by more than 3 orders of magnitude in sensitivity,\nwhile still maintaining good versatility and the ability to work under\nambient conditions. This work paves the way for subppq analysis of\norganic molecules in gas phase and even in ambient environments, which\ncan open up new research fields for trace substance analysis in atmospheric\nenvironment, clinical diagnosis, biomedical studies, etc.