Ambient mass spectrometry for extractionless analyses of plants: Holy Grail, useful tool or hoax?

Ambient mass spectrometry allows sampling on your benchtop at atmospheric pressure and often without any sample preparation. A short overview of ambient MS is given including ionisation mechanisms and new exciting developments such as leaf spray. Direct Analysis in Real Time (DART) and Desorption Electrospray Ionisation (DESI) applications from the author's group in the field of natural products chemistry are presented. In particular DART-MS is a versatile, easy to handle and fast technique allowing even quantitative measurements of secondary plant metabolites such as alkaloids, terpenes (Ginkgo, star anise) and flavonoids. Fig. A shows the DART-MS of toxic Japanese star anise with a clear peak for the neurotoxin anisatin at m/z 327.107. Chinese star anise lacks this peak (Fig. B). This result was obtained in seconds without any sample preparation. In combination with high-resolution MS it can be used for quality control, adulteration detection, metabolomics and screening of herbal products. It can also be hyphenated to HPLC or TLC. A comparison of DART and DESI-MS in terms of scope, figures of merit and limitations is made.

DART-MS spectra of Japanese (A) and Chinese star anise (B)