Electrophoretic applications

Yanes, E.G. et al.. Capillary electrophoretic application of l-alkyl-3-methyl-imidazolium-based ionic liquids. Anal. Chem., 73, 3838, 2001. 

The most widely used separation medium in CE is water, that is, an aqueous medium. If an organic solvent has been used instead, the term nonaqueous CE (NACE) is used in order to make the difference. Nonaqueous solvents were first applied to conventional electrophoresis in the early 1950s [12,13]. The first NACE experiments were carried out in 1984 by Walbroehl and Jorgenson [14] and since then they have served as alternative media to the water environment in many electrophoretic applications [15-17]. 

Smart hydrogels have found use in bioseparation. Materials responsive to temperature were used in liquid chromatography and electrophoretic applications, to separate proteins, steroids and DNA fragments. Antibody-containing materials for the concentration of antigens were also described. 

Development of electrophoretic protein separation techniques have been paralleled by improvements in protein detection methods. Protein detection in early electrophoretic applications, utilizing electrophoretic separations of solutions or colloidal suspensions from about 1816 to 1937, was limited to direct visualization of proteins coated onto microspheres, or studies of naturally colored proteins such as hemoglobin, myoglobin, or ferritin <1-4). An increase in sensitivity and the ability to detect non-colored proteins was achieved by the use of the specific absorption, by proteins, of ultraviolet light. This detection technique permitted Tiselius,in 1937, to demonstrate the quantitative electrophoretic separation of ovalbumin, serum globulin fractions and Bence Jones proteins (S). Tiselius also employed the shadows, or schlieren, created by the boundaries, due to the different concentrations of proteins in the electrophoretic system to detect protein position and concentration ( ). These detection methods served as the main methods for protein detection in the liquid electrophoresis systems. However,... 

The problem of protein-wall interactions still limits many capillary electrophoretic applications in routine biochemical analysis. Unstable migration times, poor column-to-column reproducibility, instability of siloxane-bonded layers at high pH and electric field strengths, and limited column lifetimes remain persistent problems, partially ameliorated by recent advances in coating technology, but not completely solved. 

After the application of the aluminum coating to the steel substrate, a heat treatment is often applied. Coatings resulting from vacuum deposition, electroplating, electrophoretic application, cladding, or powder coating techniques are annealed to provide adhesion by diffusion alloying [125],... 

Figure 5 Separation of poly(phenols) using (A) 1-ethyl-3-methyl-imidazolium tetrafluoroborate, (B) 1-butyl-3-methylimidazolium tetrafluoroborate, and (C) 1-ethyl-3-methylimidazolium hexafluoro-phosphate. The electrolyte solution was a 150mmoll concentration of the ionic liquid in water. The fused-silica capillary column was 50cm x 50 m ID, operating voltage 16kV, and absorbance detection at the anode end at 240nm. (Reprinted with permission from Yanes EG, Gratz SR, Baldwin MJ, Robison SE, and Stalcup AM (2001) Capillary electrophoretic application of 1-alkyl-3-methyl-imidazolium-based ionic liquids. Analytical Chemistry 73 3838-3844 American Chemical Society.)...

There are a number of materials used for the fabrication of pTAS devices. Perhaps the most common is glass due to its low cost, ease of machining, and suitability for electrophoresis and electroosmotic flow (EOF) applications without requiring surface modifications. It is also chemically inert to most reagents (apart from hydrofluoric acid and concentrated alkali). Silicon is also a valuable material that has similar chemical inermess and can easily be machined by chemical etching. While it is more expensive, it can be easily chemically etched to yield far higher aspect ratios than are possible with glass. Silicon is not suitable for electrophoresis or EOF applications without surface pretreatment. Devices fabricated from polymers such as polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS) are also frequently used due to the low cost of the material (especially important for disposable devices) and the ease of fabrication. Perhaps one drawback with polymers is their incompatibility with solvents. They are suited to electrophoretic applications but frequently require surface modification to support EOF. Occasionally, metals are used however, these are far more frequently encountered in chemical microreactors. 

Yanes EG, Gratz SR, Baldwin MG, Robison SE, Stalcup AM (2001) Capillary electrophoretic application of l-aIkyl-3-methylimidazolium-based ionic liquid. Anal Chem 73 3838-3844. doi 10.1021/ac010263r... 

To optimize such separation systems, on the one hand the nature and concentration of the chiral selector can be varied, while on the other hand the pH and organic additives (e.g., lower alcohols) make it possible to modify retention times and resolution. For electrophoretic applications, the electric field strength and the composition of the buffer ( background electrolyte , BGE) can also support enantiomer separations. 

Electrophoretic applications of this method depend on the known inverse relationship between the first-order correlation function and the power spectrum. (They are a Fourier transform pair.) With random motion the frequencies of the scattered light spread about the incident lighL producing a Lorentzian distribution (the center being at the frequency of the incident light the spectrum is known as a Rayleigh line to distinguish it from other spectral... 

---