Adsorptive stripping square‐wave voltammetric behavior of the enzyme adenosine deaminase

Abstract

The adsorptive stripping voltammetric behavior of adenosine deaminase has been studied by both square-wave and differential pulse modes, leading to analytical methodologies for its determination in aqueous samples. The application of a square-wave mode for the stripping of adsorbed adenosine deaminase has proved to be much more sensitive, yielding signals 50 times larger than those obtained by applying a differential pulse scan. The precision obtained for both voltammetric methods? at a concentration level as low as 8 ppb of the enzyme, n7as shown to be 2.47% (r.s.d~, n = 7) and 2.28% (r.s.d., n = 7 ) , respectively.KEY WORDS: Adenosine deaminase, adsorptive stripping voltammetry.

Redox kinetics in cathodic stripping square‐wave voltammetry

“…As Q: is not known the parameter log (tcZmax) = (-1.3 & 0.9) is used and the calculated rate constant is log (k,) = (0.6 k0.9) and 0.5 < Ic, < 32 cmjs. These results are in agreement with literature data [2,8,9, 221. Square-wave peak currentfrequency relationships reported for sodium sulfide [8] and sulfur containing organic molecules, such as the enzyme adenosine deaminase [2], organophosphorus pesticide dimethoate [9] and bovine serum albumine [22], are either linear [2,8,22] or slightly parabolic [9].…”

“…These results are in agreement with literature data [2,8,9, 221. Square-wave peak currentfrequency relationships reported for sodium sulfide [8] and sulfur containing organic molecules, such as the enzyme adenosine deaminase [2], organophosphorus pesticide dimethoate [9] and bovine serum albumine [22], are either linear [2,8,22] or slightly parabolic [9]. This indicates that redox reactions are either reversible [2,8,22] or quasireversible [9] in the restricted range of applied frequencies (f < 120 s- [2,9,22] or…”

“…The reduction of electrodeposited copper and mercury selenide belongs to the second group of redox reactions with immobilized reactants. Following the reduction a metallic mercury and copper amalgam are formed, while selenide anions diffuse from the electrode surface, in the same way as mercury sulfide [8] and various sulfur containing organic molecules [2,9,22]. Eventual adsorption of selenide anions at the mercury electrode surface which may occur at potentials more negative than the reduction potential, does not influence the redox reaction of copper and mercury.…”

“…It is based on the preconcentration of analyte at the electrode surface by adsorptive accumulation [2-61, or electrodeposition . Only submonomolecular layers of deposit are analytically useful [2,4,5,8,91, so the sensitivity of the technique primarily depends on the kinetics of the redox reaction in the stripping phase [lo]. In this article, an application of a previously described method for estimation of the standard rate constant of the redox reaction of immobilized reactant [I I, 121 will be presented.…”