Voltammetric Sensing and Selectivity

A variety of porous materials can be used for analytical applications. For instance, layer-by-layer hlms assembled by alternate adsorption of mesoporous silica and poly(diallyldimethylammonium chloride) onto glassy carbon electrode can be used for highly sensitive determination of ultratrace nitroaromatic compounds in aqueous solution (Shi et al., 2007). 

Voltammetric methods are of particular interest with regard to the selective determination of analytes in the presence of interferents. As a widely studied case, one can mention the determination of dopamine and other neurotransmitter catecholamines in the presence of interfering compounds, namely, ascorbic acid and/or uric acid. It is known that dopamine exerts a signilicani physiological role as extracellular chemical messenger whose loss in neurons can be associated to serious diseases such as Parkinsonism. Consequently, its determination in vitro and in vivo is an obvious target in neurochemical studies. 

FIGURE 9.9 CVs at (a) unmodified and (b) TPY fe Y-modificd glassy carbon electrodes in a 0.12 mM solution of dopamine in potassium phosphate buffer, pH 7.4. Potential scan rate 10 inV/sec. (From Domenech et al., 2002b. Anal. Chem. 74, 562-569, with permission.) 

Under optimized conditions, using differential pulse or square-wave voltammetries, linear peak current vs. dopamine concentration plots can be obtained in the 1-200 pM dopamine concentration range in the presence of 0.1 mM ascorbate, with detection limits (S/N= 3) of ca. 0.3 pM. 

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