Polymer microfluidics coupled with MALDI mass spectrometry

The offline coupling of polymer microfluidic chips to mass spectrometry (MS) through electrospray deposition of analyte onto matrix-assisted laser desorption/ionization (MALDI) targets for MALDI-MS analysis is presented. Using polycarbonate (PC) microfluidic chips with integrated hydrophobic membrane electrospray tips, selected peptides and proteins were eluted onto a stainless steel MALDI target via electrospray deposition, followed by off-line MALDI-MS analysis. A variety of matrix compositions were evaluated, and the resulting film morphology was studied via scanning electron microscopy. Microchip electrospray deposition is found to yield excellent homogeneity of peptide crystals, and exhibits significantly improved reproducibility during MALDI-MS analysis. Using this approach, a detection limit of 3.5 pmol is demonstrated for angiotensin.