A Universal Approach to Mass Spectrometry: Analysis of Solids, Liquids and Gases Using a Single Ambient Ion Source

We report the development of a panoptic ion source capable of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) in a single experiment. Together, the two ionization mechanisms allow the detection of polar, nonpolar, small organic, and large biomolecules in a single mass spectrometry experiment, without switching between ion sources. Additionally, the same ion source can analyze solids, liquids, and gases. We will discuss the mechanism enabling this universal approach to mass spectrometry. Briefly, we have developed a novel dynamic power supply, which allowed spray voltage to be applied in linear sweep, thus generating composite mass spectrum over the specified ramp period. At lower voltages, polar analytes are ionized via electrospray. Upon reaching higher voltage (>4 kV) in the ramp process, APCI is activated from the same nESI emitter allowing the ionization of nonpolar analytes, typically undetectable via nESI. The presence of nonthermal discharge allows plasma desorption, which enabled analysis of nonvolatile solids. The advantages of our method include (i) increased matrix tolerance, (ii) auto-correction of spray voltage based on analyte type and emitter tip size/shape, and (iii) simultaneous quantification of different compounds from a single mixture.