| Abstract
| - Nanoelectrospray ionization mass spectrometry is an idealtechnique for analysis of biomolecules when samplequantities are limited. With the use of this technique, 1−2μL of sample can be electrosprayed for long time periods(hours) because of the low flow rate (nanoliters perminute) attainable. However, the long-term durability ofsuch emitters has been an impediment to the routine useof nanoelectrospray. The development of longer-lastingnanoelectrospray emitters has often resulted in increasingly complex and tedious fabrication processes. Furthermore, an easily produced, reproducible, and durablenanoelectrospray emitter is the ultimately desired goal.Here, the reproducibility of the inner diameters andgeometry for nanoelectrospray emitter glass substrates isassessed using scanning electron microscopy (SEM). Theresults indicate that provided that glass pulling parameters remain constant, reproducible inner diameters canbe produced from glass capillary tubing within the samebatch; however, there are interbatch differences. In addition, SEM revealed reproducible taper geometry couldalso be obtained. Borosilicate and fused-silica nanoelectrospray emitters produced by these protocols were thencoated with polyaniline, and their analytical figures ofmerit were determined using a triple quadrupole massanalyzer. Over a 1-h run, polyaniline-coated emittersshowed fairly stable signal with coefficients of variationranging from 8.92 to 27.6%. Single-scan detection limitsbelow 1 amol were achieved for polyaniline-coated fused-silica emitters for flow rates averaging <10 nL/min.Linear mass spectrometric response with solution concentration was observed for the polyaniline-coated emitters over the range 10 nM−10 μM, with coefficients ofvariation ranging from 1.44 to 7.26%. This indicates thatwhen nanelectrospray emitter inner diameters are madereproducibly, it is possible to achieve linear quantitativeresponse for nanoelectrospray.
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