Femtosecond Laser Assisted Chemical Ionization Mass Spectrometry: Toward Sub-ppq Detection Limits for Organic Molecules.

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