Analysis of volatile compounds by open-air ionization mass spectrometry

- A simple open-air ionization mass spectrometry (MS) for direct detection of volatiles from intact solid samples is developed.
- Additional ionization methods and solvents are not required.
- Volatile compounds derived from spice samples can be readily analyzed by MS by placing spice samples close to the inlet of a mass spectrometer.
- Depending on chemical structures of volatiles, protonated/cation radical molecular ions derived from volatiles dominate the mass spectra.
- Proton source is derived from trace water vapor in the air.

This study demonstrates a simple method for rapid and in situ identification of volatile and endogenous compounds in culinary spice samples through mass spectrometry (MS). This method only requires a holder for solid spice sample (2-3 mm) that is placed close to a mass spectrometer inlet, which is applied with a high voltage. Volatile species responsible for the aroma of the spice samples can be readily detected by the mass spectrometer. Sample pretreatment is not required prior to MS analysis, and no solvent was used during MS analysis. The high voltage applied to the inlet of the mass spectrometer induces the ionization of volatile compounds released from the solid spice samples. Furthermore, moisture in the air also contributes to the ionization of volatile compounds. Dried spices including cinnamon and cloves are used as the model sample to demonstrate this straightforward MS analysis, which can be completed within few seconds. Furthermore, we also demonstrate the suitability of the current method for rapid screening of cinnamon quality through detection of the presence of a hepatotoxic agent, i.e. coumarin.

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