A large-scale free-flow electrophoresis (LS-FFE) is often too large for cell separation of lab scale, whereas micro-FFE (μFFE) has great difficulty in cell isolation due to easy blockage by cell accumulation in μFFE. In this study, a mid-scale FFE (MS-FFE) is developed for cell and protein separations. The volume of the separation chamber (70×40×0.1-0.8 mm) is from 280 μL to 2.24 mL, much lower than that in an LS-FFE but higher than that in a μFFE. Gravity is used for uniform flow of the background buffer only via a single pump with 16 channels and the sample is injected via an adjuster originally used for clinical intravenous injection. The experiments reveal that the hydrodynamic and electrohydrodynamic flows are much stable, and the Joule heat can be effectively dispersed without obvious positive or negative deviation as shown by the omega plots. By the device, Escherichia coli and Staphylococcus aureus, which easily accumulate to block μFFE and are separated with difficulty due to their same negative charges carried, can be well isolated under the conditions of 4.5 mM pH 8.5 Tris-boric buffer (4.5 mM Tris, 4.5 mM boric acid) with 0.10 mM ethylene diamine tetraacetic acid and 5% m/v sucrose, 200 μL/min, 800 V, and sample injection via inlet 4. The mid-scale FFE device could also be used for the separation of three model proteins of horse heart cytochrome c, myoglobin and bovine serum albumin. The device has clear significance for mid-scale separation of cells and proteins.

Here, a simple micro free-flow electrophoresis (μFFE) was developed for fluorescence sensing of monosaccharide via supermolecule interaction of synthesized boronic acid functionalized benzyl viologen (ο-BBV) and fluorescent dye. The μFFE contained two open electrode cavities and an ion-exchange membrane was sandwiched between two polymethylmethacrylate plates. The experiments demonstrated the following merits of developed μFFE: (i) up to 90.5% of voltage efficiency due to high conductivity of ion-exchange membrane; (ii) a strong ability against influence of bubble produced in two electrodes due to open design of electrode cavities; and (iii) reusable and washable separation chamber (45 mm × 17 mm × 100 μm, 77 μL) avoiding the discard of μFFE due to blockage of solute precipitation in chamber. Remarkably, the μFFE was first designed for the sensing of monosaccharide via the supermolecule interaction of synthesized ο-BBV, fluorescent dye, and monosaccharide. Under the optimized conditions, the minimum concentration of monosaccharide that could be detected was 1 × 10(-11) M. Finally, the developed device was used for the detection of 0.3 mM glucose spiked in human urine. All of the results demonstrated the feasibility of monosaccharide detection via the μFFE.

The significance of branched‐chain amino acids in diseases was clearly shown over the years. This review aims to describe the available techniques for their analytical determination. The article provides examples of the use of various analytical methods. The methods are divided into two categories: derivatization and non‐derivatization approaches. Separation is achieved through different chromatography or capillary electrophoresis techniques and can be combined with different detectors such as flame ionization, ultraviolet, fluorescence, and mass spectrometry. It compares the application of various derivatization reagents or detection as such for different detectors.

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