Induced Nanoelectrospray Ionization For Mitigating Clogging Of Capillary

With the development and application of new soft ionization technology,mass spectrometry(MS)technology has become one of the most rapid bioanalysis techniques in recent years.Due to the rise of native MS,however,more attentions have been paid to directly detect biomolecules in their native forms from raw biological samples.Thus,it would further challenge nESI-MS in biological applications.One challenge would be that molecules in bio-samples usually are encompassed by a native environment containing buffers that contain a variety of nonvolatile salts,like sodium chloride,potassium chloride etc.The other challenge would be that the extrem smaller tips should be required to electrospray so as to resolve the spectrum peaks of the analyte ions.However,with the application of smaller emitters,the fetal problem that has limited the wide application for nESI,clogging,became more severe,especially with small tip for spraying biological solution with nonvolatile buffers.Induced nanoelectrospray ionization(Induced nESI)is that a high voltage alternating current applied to the outside of insulating capillary with the infusion of the sample solution,the solution filled in.tip can be electrosprayed under the action of inductive alternating current.It has been demonstrated that used for chemical molecular identifications with capability to deal with raw biological samples,which normally lead to fetal clogging for conventional nESI.In this study,to mitigate the clogging problem,we applied induced alternative voltage on the nanoemitters with inner diameter(i.d.)of less 1μm(submicron-capillary),with the infusion of high concentration salt solution,to induce electrospray.The lifetime of the modified nESI was found to be 1～2 orders of magnitude longer than that of conventional nESI.Mimic intracellular fluid and extracellular fluid were also tested with both induced nESI and conventional nESI,and the mitigating effect of the induced voltage could be also confirmed.Moreover,we also determined the velocity value,and the optimal range of voltage and frequency in induced nESI process.Finally,we explored the possible reasons for avoiding clogging,wethe much longer spray time could be attributed to the re-dissolution effect and reversed electrical stress due to periodic change in the electric field direction.