Electroregenerable anion-exchange resin with triiodide carbon paste electrode for the voltammetric determination of adrenaline

Abstract

An electroregenerable carbon paste electrode modified with triiodide ions immobilized in an anion-exchange resin (Lewatit M500) is proposed for the determination of adrenaline in pharmaceutical products by differential-pulse voltammetry (DPV). Adrenaline was chemically converted into adrenochrome by the I₃⁻ ions at the electrode surface. The electrochemical reduction back to adrenaline was obtained at a potential of −0.16 V vs. Ag/AgCl (3 mol l⁻¹ KCl). A 20% decrease of the initial analytical signal was observed after 350–400 determinations; the carbon paste electrode was 100% electroregenerated at a fixed potential of +0.65 V vs. Ag/AgCl (3 mol l⁻¹ KCl) in 0.1 mol l⁻¹ KI solution for 20 min. The differential-pulse voltammograms were obtained by applying a sweep potential between 0.0 and −0.34 V, following the adrenochrome reduction at −0.16 V. Under the optimum conditions established, such as pH 6.0; scan rate 20 mV s⁻¹ and pulse amplitude 50 mV, the calibration curve was linear from 2.0 × 10⁻⁵ to 3.1 × 10⁻⁴ mol l⁻¹ adrenaline with a detection limit of 3.9 × 10⁻⁶ mol l⁻¹. The recovery of adrenaline ranged from 99.8 to 103.1% and the RSD was 2.6% for the solution containing 1.0 × 10⁻⁴ mol l⁻¹ adrenaline (n = 10). The results obtained for adrenaline in pharmaceutical samples using the proposed carbon paste electrode are in agreement with those obtained using a pharmacopoeial procedure at the 95% confidence level.