Capillary action-supported contactless atmospheric pressure ionization for the combined sampling and mass spectrometric analysis of biomolecules.

It is proposed that a short tapered capillary can be utilized as a nanoliter-volume sampling tool and sample emitter for generation of gas-phase ions in front of the mass spectrometer, without the need for using an additional electric power supply, a gas supply, or a syringe pump. A wide range of molecules can be analyzed in pure solutions and complex matrixes (cell extract, urine, and plant tissue) with no or minimum sample preparation. Singly and multiply charged ions can be detected in either positive or negative-ion mode. Because of the nanoliter-volume sampling and low spectral background, the mass detection limit for bradykinin is in the low attomole range. Other advantages include simplicity, disposability, and low cost. The putative mechanism of the ion formation in this capillary-action supported contactless spray emitter is discussed.