Optimization of electrospray ionization conditions to enhance formation of doubly protonated peptide ions with and without addition of chromium(III).

Optimization of instrument and sample preparation factors for enhanced protonation with and without Cr(III) is necessary to allow maximum formation of [M + 2H] . Proteomics researchers should find these procedures to be of use for increasing multiply protonated signal intensity even in the absence of Cr(III). Copyright © 2017 John Wiley & Sons, Ltd.