A new chemical criteria for white wine: The glutathione equivalent capacity

Determination of Thiols and Free Thiol Content in a Protein with Liquid Chromatography Coupled to Amperometric Detection at a Silver Based Carbon Paste Electrode

“…The derivative started to form within 5 min and the reaction was completed after 20 min. Amperometric experiments were performed at +0.080 V vs. Ag/AgCl based on the CV profile (Figure ) and in agreement with previous LC‐AD results at a bare silver electrode . The flow rate was varied between 0.5 and 1.0 mL/min and best results were achieved at a flow rate of 0.7 mL/min.…”

“…C and D, respectively). DTT provided a peak twice as high as Cys and GSH likely because of its two functional groups reacting with Ag and silver ions at the electrode solution interface (Figure E) . The chromatogram of a reaction mixture between Cys and 2‐DPDS gave the product 2‐TP (t R 4.51 min) and the peak of Cys had completely disappeared indicating completion of the derivatization reaction (Figure F).…”

“…Several electrochemical methods have also been reported for the determination of free sulfhydryl groups [23] with good selectivity and sensitivity achieved when combined to liquid chromatography.T he LC detector may operate by amperometry or pulsed amperometry using gold, gold amalgamatedw ith mercury,s ilver or boron doped diamond as workinge lectrode [24][25][26][27][28][29].T o the best of our knowledge,a mperometric detection coupled to LC for the assay of biomoleculesb earing thiol groups following previous derivatizationh as not been reported.S ilverw as shown to be ag ood electrode substrate for the selective determination, at low appliedp otential, of thio-compounds in the submicromolar concentration range [22][23][24][25][26][27][28][29].I ta ppeared, however, to be not sensitive to large molecules such as proteins bearing free thiol groups such ash uman serum albumin (HSA). It was thus of interest to exploitt he DPDS derivatizationr eaction for subsequent LC-amperometric detection of the liberated thiol product namely 2-TP.T he detector used in the presentw ork consistedo fasilver modified solid carbon paste electrodea si to ffered the selective reactivityo f silver towards thiols,alow baseline currenta nd it was readily prepareda nd renewed.…”

Electrochemical and Hyphenated Electrochemical Detectors in Liquid Chromatography and Flow Injection Systems for Drug Compound Analysis

“…Both the USP and European Pharmacopeia apply LC with (PAD) at a gold working electrode for the test of composition and related substances for antimicrobial compounds such as gentamicin, framycetin, amikacin, kanamycin, and tobramycin. A silver-based amperometric working electrode is the material of choice for halides, cyanide, thiocyanate, sulfide [40][41][42], and thiol-based compounds such as captopril, acetylcysteine, or aminothiols such as cysteine, glutathione, homocysteine, etc., with quantification limits in the submicromolar concentration range [6,43,44]. LC with carbon-based detectors such as those based on BDD, thanks to the high positive potentials applied, have been successful for the quantification of both oxidized and reduced forms of aminothiols [45].…”

“…LC with carbon-based detectors such as those based on BDD, thanks to the high positive potentials applied, have been successful for the quantification of both oxidized and reduced forms of aminothiols [45]. Yet a silver-based amperometric detector with an applied potential as low as 0.08 V vs Ag/AgCl reacts selectively toward aminothiols and offers less complex chromatograms as those obtained with carbon-based detectors [44,45]. The amperometric signal at the silver-based electrode corresponds to the reactivity of the analyte (halide, thiol .…”