High-resolution separation of graphene oxide by capillary electrophoresis.
ABSTRACT Separation and purification of graphene oxide (GO) prepared from chemical oxidation of flake graphite and ultrasonication by capillary electrophoresis (CE) was demonstrated. CE showed the ability to provide high-resolution separations of GO fractionations with baseline separation. The GO fractionations after CE were collected for Raman spectroscopy, atomic force microscopy, and transmission electron microscopy characterizations. GO nanoparticles (unexfoliated GO) or stacked GO sheets migrated toward the anode, while the thin-layer GO sheets migrated toward the cathode. Therefore, CE has to be performed twice with a reversed electric field to achieve a full separation of GO. This separation method was suggested to be based on the surface charge of the GO sheets, and a separation model was proposed. This study might be valuable for fabrication of GO or graphene micro- or nanodevices with controlled thickness.
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ABSTRACT: Capillary electrophoresis (CE) coupled with amperometric detection (AD) method was developed using ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4) ) as additive for the simultaneous detection of clenbuterol (CLB), terbutaline (TER) and ractopamine (RAC) in feed. The effects of detection potential, concentration of EMImBF(4) , pH and concentration of the running buffer, separation voltage as well as injection time on the separation and detection of these three β-agonists were investigated in detail. Under the optimum conditions: the detection potential at 1.05 V, 50 mmol/L Tris-HAc at pH 8.0 with 0.6% (v/v) EMImBF(4) , electrokinetic injection 6 s at 16 kV and separation voltage at 16 kV, a baseline separation for these three analytes could be achieved within 11 min. Introduction of EMImBF(4) into the running buffer resulted in significant improvement in separation selectivity and enhancement in peak currents for those β-agonists, especially for TER and RAC, which could not be separated in the running buffer without additive. The method exhibited wide linear range with limit of detection (S/N = 3) of 2 nmol/L, 1 nmol/L and 2 nmol/L for CLB, TER and RAC, respectively. The precision was determined in both intra-day (n = 5) and inter-day (n = 3) assays, and the relative standard derivations (RSDs) for both migration time and peak current were less than 6%. The proposed method was also applied to analyze β-agonists in feed sample.Electrophoresis 10/2012; · 3.26 Impact Factor