Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectometry

Abstract

Abstract An entire series of Starburst polyamidoamine (PAMAM) dendrimers consisting of generations 1 through 10 (G1–10) have been studied by positive‐ion electrospray ionization mass spectrometry (ESI‐MS) using an extended m/z range quadrupole mass spectrometer. Charge‐state distributions were detected as high as m/z 12 000 for the generation 10 dendrimer, having a theoretical molecular weight of 1 megadalton and containing approximately 93 maximum positive charges on the molecule. Accurate molecular weight determinations of the smaller generation dendrimers (G1–3, M r ∼ 1.4kDa to 6.9kDa) were obtained using a commercial triple quadrupole instrument. The unit resolution ESI mass spectra provide information on the number of incomplete reactions which may occur during polymer synthesis. The extent of gas‐phase charging observed by ESI‐MS on the entire series of macromolecules was found to exhibit a linear relationship to M , consistent with theoretical models prediciting a spherical ion structure with maximum charging controlled by Coulombic effects.