Journal of Chromatography A, 984 (2003) 121–134 www.elsevier.com / locate / chroma Exploration of the electrophoretic behaviour of borane cluster anions and of the capability of capillary electrophoresis to separate them chirally a,c b c, * ´˘ ´ ¨ Viktor Slavıcek , Bohumır Gruner , Radim Vespalec a Chemical Faculty, Technical University of Brno, Czech Republic, now Institute of Analytical Chemistry, Czech Academy of Sciences, ˘´ Veverı 97, 611 42 Brno, Czech Republic b ˘ ˘ Institute of Inorganic Chemistry, Czech Academy of Sciences, Rez, Prague, Czech Republic c ˘´ Institute of Analytical Chemistry, Czech Academy of Sciences, Veverı 97, 611 42 Brno, Czech Republic Received 17 June 2002; received in revised form 1 October 2002; accepted 31 October 2002 Abstract Mobilities of investigated boron cluster compounds in 3-(N-morpholino)propanesulfonic and phosphate buffers adjusted to pH 7 either with sodium hydroxide or with tris(hydroxymethyl)aminomethane depend on both buffer ions. The zone width and zone asymmetry, which are usually markedly higher than those of organic or common inorganic ions of comparable size, depend on the type of the borane cluster anion. Unusual shapes of zones of two investigated compounds have been found in tris phosphate buffer. Acetonitrile was superior to methanol as an organic additive to separation systems from the viewpoint of the zone symmetry and separation speed. Narrow trigonal zones, typical of organic ions non-interacting with the capillary wall, have been observed for some bridged sandwich cobalt complexes in run buffers with the addition of acetonitrile. The interaction of borane cluster anions with b-cyclodextrin cavity is excessively strong in purely aqueous solutions. Methanol and acetonitrile, which generally weaken the interaction, sometimes affect the separation enantioselectivity of various compounds in different ways in addition to the weakening effect. Chiral discrimination was reached for all ten investigated anions, which belong to four different structural types of cluster boranes. Stability constants estimated for some analyte–b-cyclodextrin complexes range between 100 and 1800 l / mol in acceptable separations. The relative difference of the constants was from 3 to 20%.  2002 Elsevier Science B.V. All rights reserved. Keywords: Enantiomer separations; Buffer composition; Cyclodextrins; Boranes; Cluster boranes 1. Introduction synthetic compounds of molecular architecture dif- ferent from that of naturally occurring compounds Cluster boranes (Fig. 1) and their derivatives are [1]. They exhibit exceptional properties that are frequently of practical interest. Cluster boranes and their derivatives to date have found use, for example, *Corresponding author. Tel.: 1420-5-3229-0121; fax: 1420-5- as extracting agents in the treatment of high-level 4121-2113. E-mail address: vespalec@iach.cz (R. Vespalec). radioactive waste [2], in neutron capture therapy of 0021-9673 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0021-9673(02)01816-2