A planar microfabricated nanoelectrospray emitter tip based on a capillary slot.
We report on the fabrication and testing of planar nib-like structures for nanoelectrospray ionization-mass spectrometry (nanoESI-MS) applications. The micro-nib structures were fabricated on silicon substrates using the negative photoresist SU-8; they include capillary slots with widths of 8 and 16 microm. A suitable wafer cleaving step made the nib-like structures overhang the edge of a silicon substrate to provide a robust interface for nanoESI-MS applications; this freeing of the nib tip from the wafer surface created a point-like structure that is essential to establish an electrospray. The micro-nib sources were successfully tested on an LCQ Deca XP+ ion trap mass spectrometer using peptide samples at concentrations down to 1 microM. The high voltage was applied using a platinum wire inserted in the sample reservoir upstream to the capillary slot. A Taylor cone was clearly seen at the nib tip. The micro-nibs performed well at voltages as low as 0.8 kV; such performances are state-of-the-art with respect to current micromachined ESI-MS interfaces and are conditions comparable to those used for standard emitter tips. In addition, we clearly observed the influence of the micro-nib slot width on the ionization performances: the narrower the slot, the better the performances.
Le Gac
Séverine
S
Laboratoire de Chimie Organique et Macromoléculaire, Université des Sciences et Technologies de Lille, Villenueve d'Ascq Cedex, France.
Arscott
Steve
S
Rolando
Christian
C
D006096:Gramicidin / Q000302:isolation & purification*; D044085:Microfluidics / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D008904:Miniaturization / Q000379:methods*; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
D006096:Gramicidin