On-column liquid–liquid–liquid microextraction coupled with base stacking as a dual preconcentration method for capillary zone electrophoresis

Low-density solvent-based solvent demulsification dispersive liquid–liquid microextraction for the fast determination of trace levels of sixteen priority polycyclic aromatic hydrocarbons in environmental water samples

“…However, traditional sample extraction procedures, based on conventional liquid-liquid extraction (LLE) are often considered to be time-consuming, labor-intensive, and environmentally unfriendly due to usage of significant amount of potentially toxic organic solvents. In the past few years, many research efforts have been oriented towards the development of efficient, miniaturized and environmentally benign sample extraction methods, such as solid-phase microextraction (SPME) [1][2][3][4][5][6] and liquid-phase microextraction (LPME) [7][8][9][10][11]. SPME, which combines extraction and pre-concentration in a single step, is an efficient and solvent-free technique.…”

Selective extraction of alkaloids in human urine by on-line single drop microextraction coupled with sweeping micellar electrokinetic chromatography

“…On-column sample preconcentration methods were performed by changing the physico-chemical property of the sample solution relative to the background electrolyte (BGE) in order to preconcentrate the analytes, such as field amplification of enhancement (field-amplified sample stacking (FASS) [10,11] and large-volume sample stacking (LVSS) [12,13]), transient isotachophoresis (t-ITP) [14][15][16], dynamic pH junction [17,18], transient moving reaction boundary (tMCRBM) [19], micelle to solvent stacking (MSS) [20,21], pH mediated stacking [22,23], acetonitrile stacking [24], analyte focusing by micelle collapse (AFMC) [25] and sweeping [26][27][28][29][30][31], etc. Since being introduced in 1998 [27], sweeping MEKC has been accepted as an attractive and powerful on-column preconcentration method because of greatly improved concentration sensitivity both for neutral and charged molecules.…”

“…Enrichment factors of 3 orders of increase were obtained within 30 min. In addition, dual sample preconcentration methods of on-line three-phase SDME coupled with stacking technique were also developed [23,41]. The combinations can not only handle complex matrices directly but also further increase the sensitivity.…”

“…The combinations can not only handle complex matrices directly but also further increase the sensitivity. For example, He et al [23] utilized pH mediated stacking (base stacking) to concentrate anionic analytes in a low conductive and field-amplified zone which resulted from the injection of hydroxyl ions into an enriched acceptor phase. Chen et al [41] relied on large-volume sample stacking combined sweeping (LVSSsweeping) without polarity switching to further concentrate the target analyte after SDME.…”

Reversed Electrode Polarity Stacking Sample Preconcentration Combined with Micellar Electrokinetic Chromatography for the Analysis of Carbamate Insecticide Residues in Fruit Juices

“…CE has advantages of simplicity, high separation efficiency, short analysis time, and low consumption of samples and reagents. Both capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) are widely used as the separation modes for the simultaneous determination of pesticides (Xie et al 2009;Rodríguez-Gonzalo et al 2008;Ravelo-Pérez et al 2007a, b, c, 2008aMolina-Mayo et al 2007;Turiel et al 2000). However, CE has a drawback of low sensitivity when compared to HPLC.…”