www.elsevier.nl/locate/carres Carbohydrate Research 319 (1999) 74 – 79 The use of solid-phase extraction with graphitised carbon for the fractionation and purification of sugars John W. Redmond, Nicolle H. Packer * Macquarie Uniersity Centre for Analytical Biotechnology, Macquarie Uniersity, North Ryde, NSW 2109, Australia Received 25 January 1999; accepted 24 May 1999 Abstract The unique selectivity, high preparative capacity and chemical inertness of graphitised carbon make it an ideal medium for the solid-phase extraction (SPE) of sugars from dilute solution, and for their analytical and preparative separation from salt, alkali or mineral acid. Graded elution with water containing an organic modifier (such as an alcohol or acetonitrile) permits the separation of groups of oligosaccharides. Acidic sugars are retained by graphitised carbon, while comparable neutral and amino sugars are eluted by water containing an organic modifier; the acidic components are then eluted by the same eluant containing trifluoroacetic acid. As such, graphitised carbon presents a much-needed solid-phase packing for the general clean-up and separation of sugars. © 1999 Elsevier Science Ltd. All rights reserved. Keywords: Chromatography; Graphitised carbon; Solid-phase extraction 1. Introduction Activated carbon (charcoal) has long been used for the preparative chromatographic fractionation of mixtures of oligosaccharides obtained by partial acid hydrolysis of polysac- charides [1–4]. In this procedure, an acid hy- drolysate of a polysaccharide is neutralized and applied to a column of activated carbon, typically dispersed in diatomaceous earth to improve its flow characteristics, and the oligosaccharides are recovered, in order of increasing size, by batch elution with water containing increasing proportions of ethanol as organic modifier [1]. With the availability of a graphitised carbon adsorbent, this mode of separation has now been adapted to analyt- ical high-performance liquid chromatography (HPLC) of sugars [5–8], typically using ace- tonitrile as organic modifier. The oligosaccha- rides are eluted in order of increasing size [6], as with the older charcoal adsorbent, and acidic sugars are retained more than neutral compounds [5,9]. We describe here the use of graphitised carbon for preparative procedures, such as the solid-phase extraction (SPE) of oligosaccharides from dilute solutions, the re- moval of salt and the fractionation of mix- tures of sugars on the basis of size or ionic character. The technique provides a solution to many traditional difficulties in the isolation and purification of sugars and can be used in a wide range of applications in the field of carbohydrate chemistry. This paper describes some of these applications using standard sug- ars to demonstrate the potential of this simple procedure. * Corresponding author. Present address: Proteome Sys- tems Ltd, Locked Bag 2073, North Ryde, 1670, Sydney, NSW, Australia. Fax: +61-2-9889-1830. E -mail address: nicolle.packer@proteomesystems.com (N.H. Packer) 0008-6215/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII:S0008-6215(99)00130-5