Folded emitters for nanoelectrospray ionization mass spectrometry

Electrospray ionization (ESI) has revolutionized mass spectrometry (MS), providing a facile method for the ionization of macromolecules for analysis by mass. The development of nanoESI-MS has further extended the utility of ESI-MS, permitting the analysis of small-volume samples with enhanced sensitivity over conventional ESI-MS. Traditional nanoESI-MS experiments use pulled-glass capillary emitters, which are expensive to purchase and require specialized instruments and training to fabricate in-house. Furthermore, these emitters suffer from problems including clogging, sample contamination, and irreproducible spray stability. Here, we report a new emitter for nanoESI-MS, made by folding small pieces of polyimide tape. In comparison with conventional pulled-glass capillary emitters, the new emitters are inexpensive and simple to make. Their low cost makes them disposable after a single use, such that sample contamination or clogging is never a problem. Emitter performance has been evaluated for diverse analytes encompassing a large mass range, including small molecules, peptides, proteins, and synthetic polymers. In all cases, the performance is similar to that of pulled-glass capillary emitters, with the advantages of low cost, ease of use, and disposability.