Online electrochemistry/electrospray mass spectrometry with a coaxial probe for investigation of electrochemical derivatization of anthracene with dodecylamine

Abstract

In the present study, a coaxial probe was used for online electrochemistry/electrospray mass spectrometry (EC/ES-MS). The probe can be constructed quickly using readily available materials at low cost. A wireless potentiostat floating at the electrospray high voltage was used to control the probe in a two-electrode configuration. Using an acetonitrile solution containing diphenylanthracene or triethylamine, we examined the performances of the probe, including the accuracy of potential control, the conversion efficiency, the response time, and the tolerance to fouling. A silver(I) salt solution (10 mmol · L -1) in acetonitrile was used as the electrolyte and depolarizer. This decreased the solution resistance of the probe to approximately 250 Ω and enabled precise potential control during online operations. Good correspondence was observed between the hydrodynamic and cyclic voltammograms of diphenylanthracene. At 3.6 μL · min -1, the response time of the probe was as low as 5 s and the conversion efficiency for triethylamine was 77%. Using the coaxial probe, we investigated the electrochemical derivatization of anthracene with dodecylamine. As a non-polar compound, anthracene usually cannot be detected by ES-MS. However, with the EC/ES-MS, the anthracene was first oxidized electrochemically, and then derivatized online by reactions with dodecylamine. The derivatization produced polar compounds that appeared in the ES-MS in high abundance. The products were identified and the reaction mechanism was elucidated. The results provide insight into the complex electrochemical behavior of anthracene. © Editorial office of Acta Physico-Chimica Sinica.