Abstract.An electrochemical anodic stripping proce-dure for ultra-trace assay of xanthine in Cu
2þ
solution
at a glassy carbon electrode (GCE) is described. Cyclic
voltammetry was used to characterize the nature of the
process taking place at the GCE. The anodic stripping
response in the presence of Cu
2þ
, at 150 mV (peak I)
and 600 mV (peak II), is evaluated with respect to
various experimental and instrumental conditions.
Voltammetric studies show that the mechanism of
the overall reaction is similar to that of the oxidation
of purine derivatives at a pyrolytic graphite electrode.
It is found that the copper metal deposited onto the
GCE was oxidized to Cu
þ
at around 180 mVvs.
Ag=AgCl and the generated Cu
þ
reacted with xanthine
to accumulate on the GCE as an insoluble compound.
The Cu
þ
-xanthine compound accumulated on the GCE
was redissolved by the oxidation of Cu
þ
to Cu
2þ
at ca.
150 mV, and the concentration of xanthine in the vicin-ity of the GCE increased. The results enabled us to use
the measurement of the oxidation peak current as the
basis of a simple, accurate and rapid method of deter-mining xanthine within a concentration range of 19.9
to 166 nM for peak (I) and 0.24 to 17.2mM for peak
(II). Promising results were obtained for xanthine
determination by using an external mixing step prior
to stripping measurements, which yielded a detection
limit of 0.138mgL
1
(9.110
10
M) xanthine. The
effect of some interferences (e.g. purine compounds,
amino acids and some metal ions) was considered