Liquid chromatographic detector for organosulphur compounds based on a ligand-exchange reaction

Determination of cysteine in pharmaceuticals via liquid chromatography with postcolumn derivatization

“…The important role that thiol compounds in general and cysteine in particular play in pharmaceutical formulations places a premium on an analytical methodology that is highly sensitive and selective for this species. While many methods have been reported for the determination of cysteine, including ion exchange chromatography (1)(2)(3)(4); spectophotometry (5)(6)(7)(8)(9)(10)(11); gas (12)(13)(14), thin-layer (15,16), and high-performance liquid chromatographies (17)(18)(19)(20)(21)(22)(23)(24)(25)(26); polarography (11); and fluorometry (27)(28)(29); these methodologies generally suffer from sensitivity, specificity, or productivity limitations. Specificity is particularly critical in most pharmaceutical applications, where the formulations may include a large number (and quantity) of structurally similar species, their degradation products, and matrix components (pH buffers, preservatives).…”

Time optimization in thin-layer chromatography

“…i.e., tL > L (10) Thus, for a given solvent composition, continuous development will always yield a shorter analysis time for a given spot separation than will conventional development.…”

Molecular and nanoparticle postcolumn reagents for assay of low-molecular-mass biothiols using high-performance liquid chromatography

“…Palladium(II)-calcein is another postcolumn reagent reported for the detection of sulfur-containing compounds based on a ligandexchange reaction [48]. The non-fluorescent reagent releases free calcein when reacted with organosulfur compounds, providing an indirect measure of the compounds via fluorescence detection.…”