Capillary electrophoretic separation enhanced by a macrocyclic dioxopolyamine additive

Abstract

Macrocyclic polyamines, or in particular dioxopolyamines, are strong receptors for analytes such as metal ions, catechol and catecholamine derivatives. In this paper, based on their interaction with a dioxopolyamine compound: 1,4,7,10-tetraazacyclotridecane-11,13-dione (or dioxo[13]aneN 4), we report its use as an additive in capillary electrophoresis (CE) to improve the separation resolution and selectivity of various model analytes. Using an imidazole–acetic acid electrolyte with dioxo[13]aneN 4 as the only additive, alkali metal, alkaline earth metal and NH 4 + ions can be effectively separated and detected by using CE with indirect UV detection, as opposed to the use of crown ether in which another additive, such as α-hydroxyisobutyric acid, is needed. The host–guest interaction between dioxo[13]aneN 4 and metal and NH 4 + ions can modify their electrophoretic mobilities, and therefore can be used to differentiate the various cations, especially between K + and NH 4 +, and between Sr 2+ and Ca 2+. We have also found that dioxo[13]aneN 4 is an effective additive in CE to resolve nitrophenols and, in particular, dihydroxybenzenes. Moreover, unlike previous reports, the separation of various biogenic monoamine neurotransmitters can be achieved at neutral or physiological pH. This work demonstrates that one of the macrocyclic dioxopolyamine derivatives: dioxo[13]aneN 4 is a promising additive in CE separations for any chemical species: cationic, anionic and neutral.