Pulsed amperometric detection (PAD) of diuretic drugs in herbal formulations using a gold electrode following ion-pair chromatographic separation

Determination of Phenolic Antioxidants in Amazonian Medicinal Plants by HPLC with Pulsed Amperometric Detection

“…In addition to methanol, the influence of acetonitrile on the mobile phase composition was also investigated. However, as observed in a previous study, [13] acetonitrile contributes to more pronounced adsorption processes on the gold electrode surface and enhances the need for manual polishing. Hence, 30% (v/v) methanol was chosen as the organic solvent in the mobile phase using a 1 mL min À1 flow rate.…”

“…When the analyte is flowing through the electrochemical cell, E 1 , E 2 , and E 3 are constantly applied to the working electrode in cycles of one or two seconds. [13] This technique allows the electrode response to remain stable over a long period of time due to electrochemical cleaning (E 2 and E 3 ), which prevents or reduces the contamination of the electrode surface. In order to investigate the optimal voltammetric potential of the studied phenolic compounds (E 1 ), a potential range from À0.30 V to þ 1.10 V was employed in direct current (DC) mode.…”

“…The application of a variety of potential-time waveforms for polarization of the working electrodes (mostly made of noble metals such as Pt and Au) leads to a decrease in the activation barrier for oxidation of the determined analytes. [12,13] In general, the potential cycling in PAD employs an oxidation potential (E 2 ) that is more positive than the detection potential (E 1 ) used to generate oxides on the gold electrode surface. The process ends at a reducing potential (E 3 ) that is more negative than E 1 and E 2 , at which the adsorbed oxidation products are desorbed from the electrode surface.…”

“…[12] HPLC-PAD approaches using a gold working electrode have been described in literature [9] for separation of phenolic acids in beverages with high sensitivity compared to spectrophotometric detection methods. Moreover, a previous work [13] using gold as a working electrode for PAD of diuretic drugs in herbal formulations showed it to be a useful analytical tool for the selective determination of drugs at low concentrations in samples of highly complex composition, such as herbal-based traditional medicines and dietary supplements. However, there are no reports regarding the use of this electrode in PAD for HPLC determination of selected flavonoids and phenolic acids in medicinal plants.…”

Voltammetric/amperometric screening of compounds of pharmacological interest

“…Determinations of anti-inflammatory drugs involved boron-doped diamond (Gimenes et al , 2013, tubular bismuth film (Rodríguez et al 2007) and glassy carbon (Silva et al 2007, Stefano et al 2012, and the amperometric screening of amiloride, chlorthalidone, furosemide and hydrochlorothiazide diuretics in herbal formulations on gold electrodes was reported recently by De Carvalho et al (2013). Hypocholesterolemic products were determined in pharmaceuticals formulations using unmodified ) and multi-walled carbon nanotubes-modified glassy carbon electrodes (Jalali et al 2010).…”