Nanoparticle-Based Continuous Full Filling Capillary Electrochromatography/Electrospray Ionization-Mass Spectrometry for Separation of Neutral Compounds

Abstract

Highly efficient reversed-phase capillary electrochromatography (CEC) separations (plate numbers up to 700 000/m), with electrospray ionization mass spectrometry detection were achieved utilizing novel dextran-coated polymer nanoparticles as a pseudostationary phase. A continuous full filling (CFF) technique in which nanoparticles are continuously introduced into the capillary was employed for separation of neutral analytes (dialkyl phthalates), utilizing an orthogonal electrospray interface to prevent nanoparticles from entering the mass spectrometer. CFF-CEC benefits from that an entirely fresh column is employed for every analysis, avoiding carryover effects associated with stationary-phase contamination. The highly efficient separations obtained were accomplished by optimizing the organic modifier concentration in the electrolyte and by using a high nanoparticle concentration (5 mg/mL), to improve interparticle mass transfer and gain sufficient retention. Nanoparticles, with an average diameter of 600 nm, were prepared by polymerization of methacrylic acid and trimethylolpropane trimethacrylate, which in turn were coated with dextran. These nanoparticles formed stable suspensions in electrolytes having broad ranges of polarities, enabling straightforward optimization of the reversed-phase conditions.

Continuous full filling capillary electrochromatography–electrospraying chromatographic nanoparticles

“…For this reason, 25% acetonitrile in both BGE and sheath liquid was found being optimal, presenting a local maximum in the surface plots ( Figure 4). Although the composition of the sheath liquid previously has remained uninvestigated the effects of the organic modifier concentration in the BGE has been investigated in two previous studies [24,25]. These studies showed, as also shown here, that the efficiency increased while the resolution decreased with increasing acetonitrile concentration in the BGE.…”

“…Thus, from these studies it can be concluded that the optimal nanoparticle concentration is 3.8 mg/mL, and that the presence of nanoparticles in the electrospray does not influence the ionization efficiency. In a previous study on CFF-CEC/ESI-MS, Nilsson et al indicated that for dextran coated polymer nanoparticles, the optimal particle concentration was 5 mg/mL [24]. However, the data was not replicated in that study and no thorough analysis of the data was performed.…”

“…In 2002, Viberg et al [23] showed that it was possible to couple nanoparticle PSP-based CEC to ESI-MS with maintained ionization efficiency in absence of disturbing background signals and ion source contamination [24][25][26]. The technique was named continuous full filling (CFF), to distinguish it from PF that had previously been the only general technique available for coupling of PSP-based separations with ESI-MS detection (Figure 1).…”

Electrophoretic Separation of Proteins in Capillaries Filled with Poly(ethylene oxide)-stabilized Silver Nanoparticles

“…7,8 NPs were also used in electrophoresis techniques, either as modifiers to the wall of capillary or microchip, [9][10][11][12] or as pseudostationary phases (PSPs) in which they were added into the running buffers. [13][14][15] NPs used as PSPs can be replaced from run to run, and the stationary carry-over effects are thus avoided, favoring sample analysis in complex matrices. 16 Since the first report by Wallingford and Ewing, 17 various NPs to date have been explored.…”

“…13 The same research group employed NPs as PSPs in separation of neutral compounds, and they reported plate numbers as high as 700000/m. 14 Chang's group employed gold nanoparticles (GNPs) as additives in CE separation of DNA fragments. [23][24][25][26] Due to the interaction of DNA fragments with the GNPs, the apparent mobilities of DNA fragments changed, and the plate numbers doubled.…”