Spray performance of microfluidic glass devices with integrated pulled nanoelectrospray emitters.

The performance of microfluidic glass devices with a monolithically integrated nanospray tip have been evaluated. The nanospray tip is generated directly on the edge of a microfluidic glass chip by a pulling step followed by HF-etching for directed formation of a sharp tip with defined emitter area. For a fair judgment of the MS-detection sensitivity, we compared the detection performance with commercial nanospray needles. For that purpose the effect of the emitter opening on the sensitivity was studied in detail for different microfluidic chips as well as for commercial nanospray needles. A comparison of the chip-nanospray device with commercial nanospray needles revealed that a comparable spray performance is obtained at similar emitter diameters. A stable electrospray could be generated at such tapered tips without any need for hydrodynamic or electroosmotic pumping. The nanospray chips were successfully applied for coupling microchip electrophoresis and mass spectrometry. For improved performance, the separation channel of the microdevice was flushed with hydroxypropylmethylcellulose (HPMC) in order to reduce analyte-wall interactions and electroosmotic flow.