Anal Bioanal Chem (2006) 385: 821–833 DOI 10.1007/s00216-006-0456-8 ORIGINAL PAPER Helle Rüsz Hansen . Spiros A. Pergantis Mass spectrometric identification and characterization of antimony complexes with ribose-containing biomolecules and an RNA oligomer Received: 3 February 2006 / Revised: 27 March 2006 / Accepted: 28 March 2006 / Published online: 13 June 2006 # Springer-Verlag 2006 Abstract Mass spectrometric techniques have been used to study the interaction of inorganic Sb(V) with biomole- cules containing a ribose or deoxyribose moiety. Electro- spray (ES) mass spectra of reaction mixtures containing inorganic Sb(V) and one of several biomolecules (adeno- sine, cytidine, guanosine, uridine, adenosine-5′-monophos- phate, adenosine-3′,5′-cyclic monophosphate, ribose, or 2′-deoxyadenosine) afforded high-mass antimony-contain- ing ions corresponding to Sb(V)–biomolecule complexes of stoichiometry 1:1, 1:2, or 1:3. The complexes were characterized by collision-induced dissociation (CID) tandem mass spectrometry (MS) using ion-trap multistage MS. The CID results revealed that Sb(V) binds to the ribose or deoxyribose moiety. Structures are proposed for the Sb– biomolecule complexes. Analysis of the reaction mixtures by reversed-phase chromatography coupled on-line to either inductively coupled plasma (ICP) MS or ES–MS showed that in solution Sb(V) forms complexes with all the analyzed biomolecules with vicinal cis hydroxyl groups. Evidence (from size-exclusion chromatography ICP–MS and direct infusion ES–MS) of complexation of Sb(V) with an RNA oligomer, but not with a DNA oligomer, supports the suggestion that the presence of vicinal cis hydroxyl groups is critical for complexation to occur. This is the first direct evidence of complexation of Sb(V) with RNA. Results obtained by studying the effect of changing reaction conditions, i.e. pH, reaction time, and Sb/ biomolecule molar ratio, on the extent of Sb–biomolecule formation suggest the reaction may be of physiological importance. Selected reaction monitoring (SRM) and precursor-ion-scanning tandem MS were investigated to determine their potential to detect trace levels of the Sb– biomolecule complexes in biological samples. Application of SRM MS–MS in combination with high-performance liquid chromatography enabled successful detection of an Sb–adenosine complex that had been spiked into a complex biological matrix (liver homogenate). Keywords Antimony . RNA . Ribonucleoside . Chromatography . Electrospray . ICP–MS Introduction Some antimony compounds are used for treatment of leishmaniasis [1]. At elevated levels, however, antimony is acutely toxic [2]; some of its species are reported to cause DNA damage [3] and Sb 2 O 3 has been assigned by the International Agency for Research on Cancer to the group of substances which are suspected human carcinogens [4]. Despite the high toxicity and therapeutic use of antimony, little is known about its biochemical mode of action, even though several studies have attempted to investigate this. More specifically, antimony has been shown to form, in vitro, complexes with several organic ligands and biomo- lecules, e.g. citric acid [5], phthalic acid [6], trypanothione [7], glutathionine [8], and N-methyl-D-glucamine [9]. It is also interesting to note that only a few organoantimony compounds have been identified in environmental and in biological samples [10–13]. This may be partially attributed to the element’ s low natural abundance and the lack of sufficiently sensitive and selective detection techniques suitable for antimony speciation analysis. Another difficulty with this type of analysis is the requirement for analytical conditions which preserve possible antimony–biomolecule complexes during extrac- tion and analysis. Complexation between chemicals used for antimony speciation must be avoided; e.g. complexa- tion with acetic acid, a commonly used chromatographic reagent, has been reported [14]. Insufficient effort has yet Electronic Supplementary Material Supplementary material is available for this article at http://dx.doi.org/10.1007/s00216-006- 0456-8 and is accessible for authorized users. H. R. Hansen . S. A. Pergantis (*) Department of Chemistry, Environmental Chemical Processes Laboratory, University of Crete, P.O. Box 2208, Voutes, 71003 Heraklion, Greece e-mail: spergantis@chemistry.uoc.gr Tel.: +30-2810-545084 Fax: +30-2810-545001