Microchim Acta 153, 57–64 (2006) DOI 10.1007/s00604-005-0386-8 Original Paper Chelate Adsorption for Trace Voltammetric Determination of Xanthosine 59-Monophosphate and Xanthosine 59-Diphosphate Yassien M. Temerk  , Moustafa M. Kamal, Mohamed S. Ibrahim, and Hossieny S. M. Ibrahim Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt Received March 1, 2005; accepted June 10, 2005; published online November 7, 2005 # Springer-Verlag 2005 Abstract. Square-wave cathodic adsorptive stripping voltammetry based on adsorptive accumulation is a very sensitive technique for the trace determination of xanthosine 5 0 -monophosphate (5 0 -XMP) and xantho- sine 5 0 -diphosphate (5 0 -XDP). The determination is based on the strong interaction of the adsorption of xanthosine phosphate compounds on a mercury elec- trode surface, forming Hg(II)-xanthate. The cathodic reduction of the accumulated Hg(II)-xanthate complex provides the basis for direct stripping measurements of the investigated biological compounds at sub- nanomolar concentration levels. Moreover, controlled adsorptive accumulation of the Cu(II) complex of xanthosine phosphate is also reported to assay trace amounts of xanthosine phosphate. The height of the sharp chelate peak of adsorbed Cu(II)-xanthate, coupled with the flat baseline, facilitates measurements at nanomolar and submicromolar concentration levels. The adsorption and the redox behaviour of the in- vestigated complexes are indicated by cyclic voltam- metry. Experimental and instrumental parameters for the quantitative determination were optimized. Statis- tical analysis of the calibration curve data is also included. Key words: Square-wave cathodic adsorptive stripping volta- mmetry; Xanthosine phosphate determination; Hg(II)-xanthate and Cu(II)-xanthate complexes. In recent years, xanthines have become an object of increasing interest. This is because of their redox properties, the role they play in biological samples used for medical purposes [1], and their adsorption properties [2, 3]. Some of these derivatives were found to be active antiviral agents or agents interfer- ing with the function of other drugs [4]. Xanthines also have cardiovascular effects in humans and play an important role in the management of asthma [5]. The biological properties of xanthines stimulated our interest in their electroanalytical trace deter- mination [6–10]. In this context cathodic stripping has been applied to determine some nucleic acid components [11–15] and their derivatives [16–19]. The reaction mechanism of nucleic acid components on a hanging mercury drop electrode (HMDE) can involve either the formation of sparingly soluble compounds with mercury [15, 20] or adsorption [21–26]. Interactions of certain organic molecule groups with mercury are considered to be important prerequi- sites for the accumulation step. However, recent experiments with metal complexes have indicated that a chemical bond with mercury is not always required for adsorption accumulation [2, 3, 27, 28].  Author for correspondence. E-mail: Temerk44@yahoo.com