Mixed-mode capillary electrokinetic separation of positional explosive isomers using sodium dodecyl sulfate and negative-β-cyclodextrin derivatives

A mixed-mode capillary electrophoretic technique has been developed for the separation of positional nitroaromatic explosive isomers. The procedure utilized two different buffer additives as pseudo-stationary phases with different selectivities towards the analytes. Sodium dodecyl sulfate (SDS) displayed selectivities for the explosives which were similar to C-18 reversed-phase HPLC. The negatively charged sulfobutyl ether-beta-cyclodextrin (SB-beta-CD), sulfated-beta-CD and succinylated-beta-CD separated the explosives on the formation of inclusion complexes with the analytes, and exhibited different selectivities for the explosives compared to SDS. A mixed pseudo-stationary phase was then formulated by combining 10 mM SB-beta-CD, 30 mM SDS and 10% acetonitrile in 20 mM borate at pH 9 to resolve the two most difficultly separated pairs: 1,3-dinitrobenzene/1,4-dinitrobenzene and 3-nitrobenzene/4-nitrobenzene. (C) 1998 Elsevier Science B.V. All rights reserved.