Electrophoretic behavior of anionic triazine and pamam dendrimers: methods for improving resolution and assessing purity using capillary electrophoresis

The synthesis and characterization of second- and third-generation triazine dendrimers bearing carboxylic acid groups on the periphery are reported. These materials were synthesized by exhaustive succinylation of amine-terminated dendrimers. ¹H and ¹³C NMR spectra are consistent with the desired products, but these techniques are limited by degeneracy in signals. MALDI-TOF mass spectrometry confirms the presence of the desired material. These materials display pH-dependent solubility in water. Capillary electrophoresis proves to be valuable in multiple elements of this work, and general protocols emerge that appear to be useful for the characterization of lower-generation anionic dendrimers. Specifically, capillary electrophoresis provides a convenient method for monitoring the removal of excess succinic anhydride/succinic acid and offers additional clues to the chemical nature of the impurities in these samples. Optimization of the background electrolyte and instrumental parameters allows for the assessment of the purity of these triazine targets as well as comparison with two sets of commercially available anionic poly(amidoamine) (PAMAM) dendrimers. Corroborative information from the different orthogonal analytical techniques employed supports the hypothesis that triazine dendrimers exist as very narrowly disperse mixtures of macromolecules approaching, in some cases, single chemical entities.