Reactive Olfaction Ambient Mass Spectrometry

Chemical
ionization of organic compounds with negligible vapor
pressures (VP) is achieved at atmospheric pressure when the proximal
sample is exposed to corona discharge. The vapor-phase analyte is
produced through a reactive olfaction process, which is determined
to include electrostatic charge induction in the proximal condensed-phase
sample, resulting in the liberation of free particles. With no requirement
for physical contact, a new contained nano-atmospheric pressure chemical
ionization (nAPCI) source was developed that allowed direct mass spectrometry
analysis of complex mixtures at a sample consumption rate less than
nmol/min. The contained nAPCI source was applied to analyze a wide
range of samples including the detection of 1 ng/mL cocaine in serum
and 200 pg/mL caffeine in raw urine, as well as the differentiation
of chemical composition of perfumes and beverages. Polar (e.g., carminic
acid; estimated VP 5.1 × 10–25 kPa) and nonpolar
(e.g., vitamin D2; VP 8.5 × 10–11 kPa) compounds
were successfully ionized by the contained nAPCI ion source under
ambient conditions, with the corresponding ion types of 78 other organic
compounds characterized.