Determination of Thiols by Capillary Electrophoresis with Amperometric Detection at a Coenzyme Pyrroloquinoline Quinone Modified Electrode

Abstract

A chemically modified electrode has been developed as a detector for the sensitive and selective determination of thiol-containing compounds following capillary electrophoresis separation. Electrodes were constructed by entrapment of the coenzyme pyrroloquinoline quinone (PQQ) into a polypyrrole (PPy) matrix on a 245-microm graphite electrode during electropolymerization of pyrrole in the presence of PQQ. PQQ serves as an efficient biocatalyst to mediate the oxidation of thiols at a substantially reduced overpotential relative to an unmodified electrode. Furthermore, this design takes advantage of the pH-dependent reversible electrochemical properties of PQQ, which facilitates optimization of separation and detection conditions. The PQQ/PPy-modified electrode was incorporated as an end-column detector, and a separation of homocysteine, cysteine, N-acetylcysteine, and glutathione was developed. Detection limits for these four thiols were determined to be 11, 23, 104, and 134 nM, respectively, with mass detection limits ranging from 0.29 to 3.48 fmol. The PQQ/PPy electrode was also found to be very reproducible in run-to-run, day-to-day, and electrode-to-electrode comparisons. The utility of this electrode was demonstrated for the detection of cysteine in dietary supplements and human urine, resulting in excellent agreement with reported values.

Optimized Method for Determining FreeL-Cysteine in Rat Plasma by High-Performance Liquid Chromatography with the 4-Aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole Conversion Reagent

“…7) Among these, methods using HPLC with fluorescence detection are the most popular because of their high sensitivity and reasonable simplicity. The thiols in a sample are detected by converting with such fluorescence reagents as ortho-phthalaldehyde (OPA), 8) monobromobimane (mBBr), 9) N-(1-pyrenyl)-maleimide (NPM), 10) and benzofurazan reagents including 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F) 11) and 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (ABD-F).…”

Bioanalytical profile of the l-arginine/nitric oxide pathway and its evaluation by capillary electrophoresis

“…Microchipintegrated CEECD has been developed and tested with biomedical samples, showing excellent analytical performance and good technological potential for microfabrication [335]. The effort to develop CEECD applications focuses on the analysis of neurochemically and metabolically important small biogenic and essential molecules, including amino acids [336][337][338][339][340][341][342], monoamines [343][344][345][346][347][348][349][350][351][352], excitatory and inhibitory neurotransmitters with low electrochemical activity [342,353], and some vitamins and cofactors such as ascorbic acid and glutathione [354][355][356][357][358][359][360][361][362][363][364].…”

l -Cysteine determination in embryo cell culture media using Co (II)-phthalocyanine modified disposable screen-printed electrodes

“…In consideration of the aforementioned reasons the development of a facile, rapid and cost effective method for the L-CySH determination within embryo cell culture media and other biological samples for clinical applications is significant [2]. A vast number of analytical methods have been employed with this purpose, including both high performance liquid chromatography and capillary electrophoresis coupled to fluorescence [13,14], UV-Vis spectroscopy [15,16], mass spectrometry [17,18] and electrochemical detectors [19,20], as well as methodologies based on fluorescence microscopy [21] and chemiluminescence [7,22]. Nonetheless, although those analytical methods are sensitive, selective and accurate, they are time-consuming, require sample preparation and handling, and are unfeasible for routine analysis [5,6,23].…”