Characterization of a Porous Nano-electrospray Capillary Emitter at Ultra-low Flow Rates

Biopharmaceuticals, especially therapeutic monoclonal antibodies, have emerged as a very promising new generation of protein-based drugs. However, their comprehensive analysis continues to pose new challenges for the bioanalytical field. Hyphenation of capillary electrophoresis with electrospray ionization (CE-MS) is a promising technique to address these challenges. One of the main advantages of CE-MS is the ability to produce stable electrospray at ultra-low flow rates (5-20 nl/min range). In this short communication we report on the characterization of a porous nano-electrospray capillary emitter focusing on the effects of ultra-low flow rate on ionization efficiency, ion suppression and detection sensitivity. Ion suppression effect of a poorly-ionizable sugar in the presence of an easily-ionized peptide was reduced by almost 2-fold. Intact therapeutic antibody infusion analysis demonstrated that MS detection sensitivity increased by an order of magnitude with the decrease of flow rate from 250 nL/min to 20 nL/min using the nano-electrospray capillary emitter.