Journal of Chromatography A, 1282 (2013) 172–177 Contents lists available at SciVerse ScienceDirect Journal of Chromatography A j our na l ho me p ag e: www.elsevier.com/locate/chroma Short communication Evaluation and comparison of various separation techniques for the analysis of closely-related compounds of pharmaceutical interest Charlotte Gourmel a , Alexandre Grand-Guillaume Perrenoud a , Laura Waller a , Emilie Reginato a , Joelle Verne b , Bertrand Dulery b , Jean-Luc Veuthey a , Serge Rudaz a , Julie Schappler a , Davy Guillarme a,∗ a School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Boulevard d’Yvoy 20, 1211 Geneva 4, Switzerland b Sanofi Aventis Research & Development, 16 rue d‘Ankara, 67000 Strasbourg, France a r t i c l e i n f o Article history: Received 13 November 2012 Received in revised form 21 January 2013 Accepted 23 January 2013 Available online 1 February 2013 Keywords: Diastereoisomers Z/E isomers UHPLC Convergence chromatography NACE SFC a b s t r a c t The aim of the present work was to compare various separation techniques for the fast analysis of closely- related compounds, including structurally-related compounds, positional isomers, diastereoisomers, Z/E isomers. Three analytical techniques were evaluated, namely ultra high performance liquid chromatogra- phy (UHPLC), ultra high performance supercritical fluid chromatography (UHPSFC), both with sub-2 m particles, and capillary electrophoresis (CE) using non-aqueous solvents. To fairly compare the three analytical techniques, only two starting conditions for further method development were considered. All the selected mobile phases or background electrolyte were MS-compatible. As expected, CE often provided excellent results for the analysis of basic compounds but it was difficult to find out conditions that could be widely applied. On the other hand, UHPLC and UHPSFC were more generic and the per- formance was better than CE for the analysis of neutral and acidic compounds. In all cases, the analysis time was systematically lower than 3 min. In conclusion, UHPLC was the most versatile strategy for the analysis of closely-related compounds and should be tested in a first instance. UHPSFC and CE approaches offered some drastic changes in selectivity and should be considered a second choice to reach alternative selectivity as they also allow high throughput separations. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Baseline resolution of closely-related compounds (e.g. posi- tional isomers, diastereoisomers, Z/E isomers) is hardly achieved using a single separation technique because their physico-chemical properties are similar. To enhance performance in liquid chro- matography (LC), supercritical fluid chromatography (SFC), and capillary electrophoresis (CE)-based techniques, there have been some significant advances allowing for improvement in efficiency, selectivity, and/or decreasing analysis time [1,2]. In LC, some considerable progresses have been made on column technologies and instrumentations with the introduction of short, narrow bore columns packed with fully porous sub-2 m parti- cles [3–5] or sub-3 m core–shell particles [6–8]. The use of such column technologies allows a reduction of analysis time by a fac- tor 3–10 compared to conventional LC, while maintaining similar kinetic performance [9]. SFC is a powerful technique, due to the low viscosity of the supercritical fluid, resulting in fast diffusion of the compounds in the mobile phase and low pressure drop in the ∗ Corresponding author. Tel.: +41 22 379 34 63; fax: +41 22 379 68 08. E-mail address: davy.guillarme@unige.ch (D. Guillarme). column [10]. Similarly to LC, sub-3 m core-shell technology [11] and sub-2 m fully porous particles [12] were recently launched for SFC, to further improve kinetic performance and reduce anal- ysis times. CE remains scarcely employed in the industry despite numerous intrinsic advantages, such as very limited consumption of sample and solvent consumption, absence of expensive station- ary phases, and high kinetic performance [9]. Various modes of CE were proposed to address numerous difficult analytical issues, and non-aqueous capillary electrophoresis (NACE) appears as a promis- ing approach, particularly because of its full compatibility with MS [13]. The goal of the present study was to explore the possibilities and limitations of three separation modes, for the fast analysis of various families of closely-related compounds of pharmaceutical interest, possessing diverse physico-chemical properties. 2. Experimental 2.1. Chemical and reagents Methanol was of HPLC grade (Hipersolv Chromanorm) and obtained from VWR international (Dublin, Ireland). Formic acid was provided by Merck (Darmstadt, Germany). Acetonitrile, 0021-9673/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.chroma.2013.01.095