Regarding Emitter Positioning for Nanoflow Electrospray Ionization with a High-Capacity Inlet Capillary.

Nanoflow electrospray ionization is commonly used for proteomics due to its high sensitivity. Signal intensity, however, is dependent on optimal emitter positioning relative to the mass spectrometer inlet. Here, we characterize the effect of varied emitter positions on peptide signal intensity in all three dimensions using emitters and flows consistent with standard proteomic analyses. We observe improved signal robustness to x/y variations at increasing z distances and demonstrate that positioning within 1 to 2 mm of the optimal location will maintain consistent signal. Signal intensity behavior is consistent across the m/z range, suggesting emitter positions do not need to be fine-tuned for different analytes for proteomics analyses. These results provide insight for proteomics researchers using nanoflow LC-MS/MS.