MANIPULATION OF ELECTROSPRAY GENERATED DROPLETS USING VARIOUS VAPORS

Volatile reagents can be entrained in desolvation gas to manipulate electrospray generated droplets. These reagent vapors are admitted into the atmospheric interface region of a QqTOF tandem mass spectrometer. The electrospray droplets interact with the reagent vapors between the curtain and orifice plate for approximately a millisecond, which is the time required for analyte desolvation. A variety of vapors, particularly polar aprotic vapors, can be used to reduce alkali metal adduction on proteins. This effect is due to the alkali metals interacting with the vapor to form alkali metal adducted reagent vapor cluster ions that are ionized via the ion evaporation model, which reduces the amount of alkali metal in the electrospray droplet available to adduct to proteins that are ionized via the charge residue model. Polar vapors can be used to stabilize noncovalent protein complexes via evaporative cooling of the analyte of interest and lengthening the electrospray ionization desolvation process. These vapors interact with peptide containing ESI droplets to form peptide ions that are adducted to the respective vapor that was doped into the curtain gas. Additionally, these vapors interact with ESI droplets to form unique doubly charged cluster ions of the form [nX+H+Y]2+ where X is a reagent vapor molecule, n = 5-6 and Y is a sodium or potassium ion