Preventing Electrolysis of Analytes in Electrospray Ionization Mass Spectrometry using a Redox Polymer Coated Emitter

摘要

Use of surface tethered redox buffers (poly(pyrrole) (PPy), poly(3,4-ethylenedioxypyrrole) (PEDOP)) successfully prevented the undesired inherent oxidation of analytes during ESI-MS experiments. (1) Using a bare gold emitter extensive oxidation of the compounds tested (reserpine, amodiaquine, hydroquinone) can be observed. (2) The oxidation of reserpine having higher oxidation potential than that of the polymers has been completely prevented using either polymer. (3) In case of amodiaquine with oxidation potential being close to that of PPy, the oxidation was inhibited for a shorter period of time using PPy. (4) Reduction/recharging of PPy has been implemented between analyte injections by switching to negative ion mode. The reduction of the polymer layer was necessary to reinstate its redox buffer performance and capacity. (5) The redox buffering capacity of the surface tethered system can be increased and the duration of efficient redox buffering can be extended by increasing the charge capacity of the polymer layer. This was accomplished by increasing the thickness of the polymer film. (6) Using a PEDOP coated emitter electrode having lower redox potential than that of PPy, the oxidation of the amodiaquine can be successfully avoided.