Enhancement of the conductivity detection signal in capillary electrophoresis systems using neutral cyclodextrins as sweeping agents

Abstract

Conductivity detection is a universal detection technique often encountered in electrophoretic separation systems, especially in modern chip-electrophoresis based devices. On the other hand, it is sparsely combined with another contemporary trend of enhancing limits of detection by means of various preconcentration strategies. This can be attributed to the fact that a preconcentration experimental setup usually brings about disturbances in a conductivity baseline. Sweeping with a neutral sweeping agent seems a good candidate for overcoming this problem. A neutral sweeping agent does not hinder the conductivity detection while a charged analyte may preconcentrate on its boundary due to a decrease in its effective mobility. This study investigates such sweeping systems theoretically, by means of computer simulations, and experimentally. A formula is provided for the reliable estimation of the preconcentration factor. Additionally, it is demonstrated that the conductivity signal can significantly benefit from slowing down the analyte and thus the overall signal enhancement can easily overweight amplification caused solely by the sweeping process. The overall enhancement factor can be deduced a priori from the linearized theory of electrophoresis implemented in the PeakMaster freeware. Sweeping by neutral cyclodextrin is demonstrated on an amplification of a conductivity signal of flurbiprofen in a real drug sample. Finally, a possible formation of unexpected system peaks in systems with a neutral sweeping agent is revealed by the computer simulation and confirmed experimentally.

Dynamic computer simulations of electrophoresis: 2010–2020

“…Excellent agreement between simulation (lower graphs) and experimental (upper graphs) data was obtained [ 37 ]. SIMUL5complex was also employed to elucidate the impact of the complexation of buffer constituents with neutral agents on common buffer properties [ 189 ] and analyte and system peaks [ 190 , 191 ], to provide insight into the sweeping process of a drug in presence of a neutral CD [ 191 ], to study affinity capillary electrophoresis and vacancy affinity capillary electrophoresis methods that are used for the determination of complexation constants for two cases, a fully charged analyte with a neutral selector and an uncharged analyte with a charged selector [ 192 ], and to validate the applicability of a new theoretical formula derived from partial‐filling affinity capillary electrophoresis for the determination of apparent stability constants of analyte–ligand complexes [ 193 ].…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…To overcome this limitation, sweeping can be performed with a neutral pseudophase. Boublik et al studied such systems theoretically using combination of computer simulations and experimental data and a model provided for a reliable prediction of the enrichment factor. It was revealed that the conductivity signal was remarkably affected by slowing down the analyte, therefore, the cumulative signal enhancement can easily overweight amplification caused solely by the sweeping phenomenon.…”

Contemporary chiral simulators for capillary zone electrophoresis

“…The dynamic simulators GENTRANS and SIMUL5complex were applied to characterize the migration and separation of enantiomers in CZE , CITP , and CEC , to investigate electromigration dispersion effects caused by complexation , and to study the impact of complex mobilities and complexation constants on migration order and separation of drug enantiomers and profens . SIMUL5complex was used to elucidate the impact of the complexation of buffer constituents with neutral agents on common buffer properties and analyte and system peaks in CZE , and to provide insight into the sweeping process of a drug in presence of a neutral CD . Furthermore, the fundamentals of field‐amplified electrokinetic injection of cations for enantioselective CZE with sulfated β‐cyclodextrin (S‐β‐CD) , the characterization of isomer mixtures of S‐β‐CD , the investigation of the enantioselective separation of weak bases in an on‐line CZE microanalysis configuration comprising S‐β‐CD as selector , and the exploration of inverse cationic ITP for separation of methadone enantiomers with S‐β‐CD as chiral selector were also studied with this simulator.…”