At-line coupling of surface-enhanced resonance Raman spectroscopy and reversed-phase ion-pair chromatography

Recent developments in quantitative SERS: Moving towards absolute quantification

“…This work is notable as it established for the first time that LC-SERS could be performed online; at the time other workers had only achieved off-line analysis by deposition of the eluent into wells containing SERS substrates (see for e.g. [85,86]). More recently, an improved on-line LC-SERS system using reversed phase LC, where enhanced analyte separation was possible by programming the mobile phase during elution, showed that it was possible to target and quantitate methotrexate and its major metabolite 7-hydroxy methotrexate in urine from human patients suffering from rheumatoid arthritis [87].…”

Achievements in resonance Raman spectroscopy

“…In that approach the LC effluent is deposited on the surface of a moving TLC plate while the eluent is simultaneously evaporated, so that an immobilized LC chromatogram is obtained. Next, small amounts of silver colloid are added to the analyte spots and SERRS spectra are recorded [103].…”

At-line coupling of capillary electrophoresis and surface-enhanced resonance Raman spectroscopy

“…The second alternative involves analyte adsorption on a silver colloid layer, a condition not directly compatible with liquid flow systems. Therefore, in LC especially the at-line mode of operation has attracted much interest [6,7].…”

“…In previous publications we used TLC plates in at-line LC -SERRS to analyse basic and acidic dyes [6,7]. The same acidic dyes are used here in at-line CE -TLC-SERRS.…”

“…These additives also induce aggregation of the silver particles, which causes improved surface enhancement [13 -15]. In LC, the presence of a splitter and a stream of heated nitrogen gas was necessary for an efficient spraying of the effluent on the silica TLC plates and to prevent the spreading of the effluent on such plate [6,7]. With CE the flow from the separation capillary is very low and can therefore be directly deposited on the TLC plate without any splitting or a heated gas flow.…”