Pulsed electrochemical detection of nonchromophoric compounds following capillary electrophoresis

Abstract

Pulsed electrochemical detection (PED) following capillary electrophoresis (CE) has been applied to the direct detection of polar aliphatic compounds. These compounds typically have poor optical detection properties and are considered to be electroinactive under constant applied potentials. The voltammetric responses at microelectrodes of model compounds were studied under various buffers and pH conditions. The detection of unsubstituted carbohydrates requires highly alkaline conditions, whereas amine-containing compounds (e.g., glycopeptides, peptides, and amino acids) and thiocompounds can best be detected at mildly alkaline (i.e., pH 9.0) and mildly acidic (i.e., pH 5.5) conditions, respectively. In a comparative study of pulsed amperometric detection (PAD) and integrated pulsed amperometric detection (IPAD), IPAD is determined to be better suited to manage the large oxide-formation backgrounds, which accompany oxide-catalyzed detections of amine- and sulfur-containing compounds. IPAD results in more stable baselines, eliminates oxide-induced artifacts, and often yields lower limits of detection. Mass detection limits under optimal conditions are typically 10 fmole or less. This paper delineates PED waveform parameters for the optimal detection of underivatized nonchromophoric compounds of biological significance in various operating buffers and electrolytes.

Applications of Microelectrodes in Capillary Electrophoresis/Electrochemical Detection

“…LaCourse et al reported the determination of nonchromophorics, thiols, disul®des by PAD and integrated pulsed amperometric detection (IPAD) following CE. IPAD is better suited to manage the large oxide-formation backgrounds accompanied by oxide-catalyzed detection of amine-and sulfur-containing compounds [83,84]. It is the ®rst group to report IPAD coupled with CE.…”

Applications of capillary electrophoresis with electrochemical detection in pharmaceutical and biomedical analyses

“…Advantages of PAD over chemically modified electrodes include the fact that PAD can be operated over a wider pH range and will generally have a longer lifetime. It has been used for the determination of a host of sulfur compounds, including thiols and disulfides [74,75]. Detection limits using optimized PAD were typically 0.5 mM for cysteine, glutathione, and glutathione disulfide.…”

“…Some peptides and proteins were detected. LaCourse and Owens [74] used CE-PAD for the determination of amino acids in mildly alkaline conditions. Fermier and Colon [97] determined the amino acids by CE-AD at a nickel microelectrode under alkaline conditions.…”

Detecção eletroquímica em eletroforese capilar

“…PAD com eletrodos de cobre ou ouro tem sido largamente aplicada na análise de carboidratos [220][221][222][223][224][225][226][227] . Além disso, PAD pode ser utilizada com sucesso na análise de íons metálicos 228,229 , aminoglicosídeos 230 , aminoácidos 226 e compostos com grupos contendo enxofre 226,231 .…”

“…Além disso, PAD pode ser utilizada com sucesso na análise de íons metálicos 228,229 , aminoglicosídeos 230 , aminoácidos 226 e compostos com grupos contendo enxofre 226,231 .…”