W. Diewald et al., VOLTAMMETRIC BEHAVIOR OF THALLIUM(III) AT A SOLID HETEROGENEOUS CARBON ELECTRODE USING ION-PAIR FORMATION, Analyst, 119(2), 1994, pp. 299-304
Thallium in its trivalent state forms very stable [TIX(4)]-complexes w
ith halides in corresponding acidic media. Tetrahalogenothallates(III)
are able to produce ion pairs with suitable positively charged counte
r-ions in aqueous solutions. These ion pairs, each possessing distinct
lipophilic character, could be accumulated directly onto the surface
of carbon paste electrodes without applying a potential (open circuit
conditions). The nature of the electrode material and of the counter-i
on respectively, influences the adsorptive behaviour of the ion pair s
ignificantly. Best results were obtained by using anew type of heterog
eneous carbon electrode employing a solid binder (phenanthrene) instea
d of the commonly used pasting liquid. With respect to the counterions
, tetraphenylphosphonium and tetrabutylammonium proved to be the best.
Parameters influencing the optimum conditions for the analytical proc
edure (pH, counter-ion concentration, etc.) were investigated. The rel
ationship between current signal and concentration of thallium, and it
s dependence on the accumulation time were studied. The detection limi
t was found to be less than or equal to 10 mu g kg(-1), signals were r
eproducible within an s(r) of 7.7% for a thallium concentration of 1 m
g kg(-1). The interference of other ionic species was also evaluated.
The method was employed for the determination of thallium in lead- and
cadmium-containing zinc alloys.