Pulsed electrochemical detection of sulfur-containing compounds was successfully investigated by applying a four-step potential waveform at a gold working electrode. This potential waveform called APAD, which stands for activated pulsed amperometric detection, is composed of an activation potential step added to a conventional three-step potential waveform. A key advantage of the APAD at the Au electrode is the ability to enhance sensitivity through the use of a short potential pulse (Eact = +750mV versus Ag|AgCl and tact ≈90 ms) during which the formation of redox active species (presumably OH•) are able to efficiently oxidize organosulfur compounds. The APAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of lipoic acid, biotin, iminobiotin, methionine, cystine, cysteine, homocysteine, homocystine, N-acetylcysteine and glutathione, following their separations by high-performance anion-exchange chromatography (HPAEC) using alkaline mobile phases. The detection limits (S/N = 3, 10 L injected) ranged from 0.3 for cysteine (400 pg) to 0.02 mol/L for biotin (50 pg) and methionine (30 pg). The response of sulfur-, amine- and alcohol based compounds was compared by using four selected pulsed potential waveforms. It was found that the APAD exhibits excellent sensitivity for thiocompounds outperforming all other pulsed potential waveforms. Ratios of the peak areas for APAD and the six-step potential integrated waveform increased from 3.2±0.4 to 13.5±0.6 for lipoic acid and biotin, respectively.
A pulsed potential-waveform displaying enhanced detection capabilities towards sulfur-containing compounds at a gold working electrode
NARDIELLO, DONATELLA
2005-01-01
Abstract
Pulsed electrochemical detection of sulfur-containing compounds was successfully investigated by applying a four-step potential waveform at a gold working electrode. This potential waveform called APAD, which stands for activated pulsed amperometric detection, is composed of an activation potential step added to a conventional three-step potential waveform. A key advantage of the APAD at the Au electrode is the ability to enhance sensitivity through the use of a short potential pulse (Eact = +750mV versus Ag|AgCl and tact ≈90 ms) during which the formation of redox active species (presumably OH•) are able to efficiently oxidize organosulfur compounds. The APAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of lipoic acid, biotin, iminobiotin, methionine, cystine, cysteine, homocysteine, homocystine, N-acetylcysteine and glutathione, following their separations by high-performance anion-exchange chromatography (HPAEC) using alkaline mobile phases. The detection limits (S/N = 3, 10 L injected) ranged from 0.3 for cysteine (400 pg) to 0.02 mol/L for biotin (50 pg) and methionine (30 pg). The response of sulfur-, amine- and alcohol based compounds was compared by using four selected pulsed potential waveforms. It was found that the APAD exhibits excellent sensitivity for thiocompounds outperforming all other pulsed potential waveforms. Ratios of the peak areas for APAD and the six-step potential integrated waveform increased from 3.2±0.4 to 13.5±0.6 for lipoic acid and biotin, respectively.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
