Micelle to solvent stacking of two alkaloids in nonaqueous capillary electrophoresis

The advances of electromigration techniques applied for alkaloid analysis

“…The method originally presented by Quirino () was modified by resorting to the idea of shortening the organic solvent‐rich solution to a short plug injection after the introduction of the sample. In effect, sensitivity improved up to three orders of magnitude (Zhu et al ., ), which is better than for injection of the whole capillary sample under the same technique (Zhu et al ., ).…”

“…Thus, the achieved signal enhancement is usually lower than that obtained with electrokinetic injection. Nevertheless, many techniques based on pressurized sample dosing have been employed to enhance the signal, namely, field-amplified sample stacking (FASS; Kreft et al, 2000;Zhang et al, 2007;Sanchez-Hernandez et al, 2010, 2011Mercolini et al, 2010), moving reaction boundary stacking (MRBS; Wang et al, 2007c) and micelle to solvent stacking (MSS; Zhu et al, 2011bZhu et al, , 2011c; Table 1). Application of the latter has demonstrated especially good results with the detection limits of a few nanograms per milliliter reached in the analysis of human urine samples.…”

On-line sample concentration and determination of cationic alkaloids in human plasma by micelle to solvent stacking in capillary zone electrophoresis

“…To overcome this problem, some on-line preconcentration strategies have been developed to increase the sensitivity of CE, such as field amplification [20], dynamic pH junction [21], transient isotachophoresis (tITP) [22], isotachophoresis by acetonitrile stacking [23,24] and sweeping [25] or sweeping in couple with other techniques [26][27][28][29]. The more recent CE on-line preconcentration techniques include electrokinetic supercharging [30], analyte focusing by micelle collapse (AFMC) [31][32][33] and micelle to solvent stacking (MSS) [34][35][36][37][38][39][40][41][42]. The main advantage of the on-line preconcentration strategies is the ease of experimental manipulations without the need of modifications of the commercial CE instrumentation.…”

“…As a result, the analytes then experienced an electrophoretic inversion or reversal, resulting in an analyte accumulation at the MSSB. MSS has been applied to the analysis of cationic [34][35][36][37] and anionic [38][39][40] analytes in CZE, and cationic analytes in both MEKC [41] and nonaqueous capillary electrophoresis (NACE) [42]. Among them, Zhu et al developed an MSS-CZE method for the determination of two different cationic alkaloids (ephedrine and berberine) in human urine samples [36] and an MSS method in nonaqueous capillary electrophoresis (NACE) for the determination of berberine and jatrorrhizine in urine samples [42].…”

Application of Capillary Electrophoretic On-Line Sequential Concentration Based on Micelle to Solvent Stacking

“…MSS is a kind of technique based on this principle, in which the sample is prepared in a micellar solu-tion without an organic solvent or its aqueous solution. Because the organic solvent in the background electrolyte (BGE) affects the micellar interaction with the analytes, the effective electrophoretic directions of the analytes will reverse at the micellar to solvent stacking boundary (MSSB), therefore causing the analytes focusing [5] [6]. It was first introduced by Quirino and co-workers for the stacking of small organic cations [7] and has already been widely used to analyze organic cations and anions in waste water [8], traditional Chinese medicine [9] and biological fluids [10] [11] [12] analysis.…”