Determination of Solution Ions by Electrospray Mass Spectrometry

Spectral results are presented illustrating the capability of electrospray mass spectrometry (ES-MS) for the determination of the composition of solution samples. The solution components that can be determined include the elemental and molecular forms of anions and cations. Three modes of positive-ion ES-MS are described: the ion cluster mode, the metal-ion mode, and an intermediate mode. The modes are established by operating the electrospray source at specific voltages and curtain gas flow rate values, and each mode provides a unique mass spectral picture of the solution components with primary focus on cationic species (i.e., metal ions). Results are also presented for operation of the electrospray source in negative-ion mode. In this mode both elemental anions (i.e., halides) and molecular anions (i.e., oxo-anions) can be determined.