Combined liquid-liquid electroextraction and isotachophoresis as a fast on-line focusing step in capillary electrophoresis

Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

“…In the final step (F), the capillary inlet is placed into the leading buffer and CZE is started by application of separation voltage. The method has been applied to preconcentration and determination of compounds of pharmaceutical relevance in standard solutions [19][20][21], applications to real biological samples were, however, not Generalshown in these papers. EE was also presented as a suitable pretreatment and preconcentration technique for HPLC [21].…”

“…LiquidÀliquid EE in combination with capillary ITP was presented as an on-line focusing technique for CZE in [19,20]. LiquidÀliquid EE is used to focus the analyte ions from a large organic sample into a small volume in a terminating buffer zone, just above the liquidÀliquid interface.…”

“…The convective mixing, which often accompanies the LLE, was suppressed since the thermal flows could not cross the phase interfaces. LiquidÀliquid EE has later been used as a sample preparation technique in CE and LC [19][20][21]. In order to allow the electric current to flow through the two immiscible liquid phases, the non-conductive organic phase was saturated with ionic species and EE was applied as a fast on-line sample pretreatment step for the two separation methods.…”

Recent application and developments of capillary isotachophoresis

“…A decrease in the LOD by 2.3 orders of magnitude could be reached, keeping the recoveries at the 98-100% level. An interesting method is the combination of CITP with liquid-liquid electroextraction where the capillary with an initial L/T system is plunged into the vessel with a nonaqueous extract of the analyte(s) [72]. Al1 the analytes are transferred by electromigration into the aqueous phase within the very short time of a few minutes; then normal ITP is continued in order to reach the steady-state ITP configuration; and …”

Electromembrane Extraction from Biological Fluids

“…Van der Greef et al reported early attempts of analytical EE in the period 1994 -1996. [3][4][5] Three research papers demonstrated EE of charged substances from an organic solvent (ethyl acetate) and into aqueous solutions for subsequent analysis by CE or HPLC. Thus, conventional LLE was performed prior to EE when the technique was used for aqueous samples such as biological fluids.…”