Chelate Adsorption for Trace Voltammetric Determination of Xanthosine 59-Monophosphate and Xanthosine 59-Diphosphate

Square-wave cathodic adsorptive stripping voltammetry based on adsorptive accumulation is a very sensitive technique for the trace determination of xanthosine 50-monophosphate (50-XMP) and xanthosine 50-diphosphate (50-XDP). The determination is based on the strong interaction of the adsorption of xanthosine phosphate compounds on a mercury electrode 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 subnanomolar 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 investigated complexes are indicated by cyclic voltammetry. Experimental and instrumental parameters for the quantitative determination were optimized. Statistical analysis of the calibration curve data is also included.