| Two LC/MS interfaces, particle beam (PB) and electrospray ionization (ESI), were used to couple electrochemistry (EC) to mass spectrometry (MS), EC/MS. A homebuilt thin-layer EC flow cell was used in EC/PB/MS. Observation of the generation of tetraphenylbenzidine (TPB) radical monocation in the oxidation of triphenylamine (TPA) was achieved by EC/PB/MS. Significant enhancement of the TPA ion signal was observed in the presence of tetrabutylammonium perchlorate (TBAP) electrolyte. The signal enhancement was attributed to an improved PB mass transport in the presence of the electrolyte and a reduced fragmentation of the TPA ion in the El ion source of the mass spectrometer, due to the formation of TBAP/TPA aggregates. The signal enhancement factor was ∼35-fold. By keeping the TBAP/TPA concentration ratio constant at an optimum value, 10/1, an enhancement in PB/MS detection sensitivity and linearity of TPA calibration curves was achieved at low concentrations.;A new electrochemical flow cell was developed and coupled to an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (EC/ESI-FTICR MS). Identification of TPB dication in the presence of an interfering ion of the same m/z value was achieved based on the detection of isotopic ions. The MS detection sensitivity for TPB radical monocation and dication was greatly enhanced by EC/ESI-FTICR MS compared to ESI-FTICR MS detection. In ESI ionization, the oxidation of TPA was limited to the spray needle tip.;In EC/ESI-FTICR MS, the application of EC cell voltage significantly reduced the signal suppression problem from the TBAP electrolyte. This result showed that common electrolytes might be used in EC/ESI-MS. It was verified that flow rate and electrolyte concentration were the parameters that affect the MS detection sensitivity of transient electrochemical products.;Nucleophilic reactions of cation radicals with pyridine were also investigated by EC/ESI-FTICR MS. The MS detection sensitivity for anthracene-pyridine and perylene-pyridine adducts was significantly enhanced by EC/ESI-FTICR MS. |
