Instruments electrophoretic

Once the exclusive purview of biologists, biochemists, serologists, and DNA analysts, electrophoresis is entering the realm of small-molecule separations and consequently now plays a role in forensic chemistry. Ion mobility spectrometry 

Electrophoresis separates ions and molecules on the basis of differences in their si2e-to-chaige ratios, which in turn dictate how fast they move through an electrical field. The velocity of a charged particle or an ion in an electric field is given by 

Capillary Electrophoresis Slab-gel techniques were used in forensic serology until the late 1980s to separate and detect polymorphic serum proteins found in blood and body fluids. Around the time that DNA began to supplant traditional blood group typing in forensic serology, capillary electrophoresis (CE) was introduced to separate small molecules. Ironically, by the turn of the century, CE-based instruments dominated DNA typing. 

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Grummer, G., Knippel, E., Budde, A., Brockman, H., and Treichler, J., An electrophoretic instrumentation for the multi-parameter analysis of cells and particles, Instr. Sci. Technol., 23, 265, 1995. 

CEC is often inappropriately presented as a hybrid method that combines the capillary column format and electroosmotic flow employed in high-performance capillary electrophoresis with the use of a solid stationary phase and a separation mechanism, based on specific interactions of solutes with the stationary phase, characteristic of HPLC. Therefore CEC is most commonly implemented by means typical of both HPLC (packed columns) and CE (use of electrophoretic instrumentation). To date, both columns and instrumentation developed specifically for CEC remain scarce. 

In addition, the surface charge (or zeta potential) of suspended colloids was measured on separate pH-adjusted aliquots using a laser micro-electrophoretic instrument. These measurements were made between the pH range of 2 to 12. 

Stanislawski, B., Kaniansky, D., Masar, M., Johnck, M., Design principles, performance and perspectives of a complete miniaturized electrophoretic instrument. Micro Total Analysis Systems Proceedings jlTAS 2002, symposium, 6th, Nara, Japan, Nov. 3-7, 2002, 2000, 350-352. 

Electrophoretic instruments for analysis of colloidal suspensions can be divided into two basic classes optical instruments for which the operator observes the migration of particles in a field using a microscope and laser-based instruments that measure the Doppler shift in the frequency of the scattered light from particles... 

The initial cost of equipment and the expense of maintenance for electrophoresis is generally significantly lower than for ion chromatography and atomic spectroscopy. Thus, commercial electrophoretic instruments are marketed in the price range of 10,000 to 65,000. ><>... 

Rashkovetsky, L.G. Lyubarskaya, YV Foret, R Hughes, D.E. Karger, B.L. Automated Microanalysis Using Magnetic Beads with Commercial Capillary Electrophoretic Instrumentation, J. Chromatogr., A 781(1 -F 2), 197-204 (1997). 

Our laboratory has recently been selected by the National Aeronautics and Space Administration (NASA) as one of its two national centers of excellence in separation science. This has given us an opportunity to broaden our efforts towards the advancement of all modes of electrophoresis for large scale processing. Thus, our Center has been chosen by European manufacturers as the demonstration site for the United States of two unique electrophoretic instruments. 

At the other size extreme are electrophoretic "instruments" for separating large quantities (grams to Kilograms) of materials for preparative purposes. Here, due to the large size of the equipment, heat dissipation can become a major problem to be dealt with. More information on electrophoresis on a preparative scale can be found in chapter 16. 

Similarly to gel electrophoresis, a number of modes can be employed that separate analyte mixtures according to different properties. Some of these modes are summarised in Table 3.2 together with their commonly used abbreviations. Depending on the principle of separation, different species can be analysed. After an overview of capillary electrophoretic instrumentation, the different modes of capillary electrophoresis are described in more detail including capillary zone electrophoresis (CZE), capillary isoelectric focussing (CIEF), micellar electro-kinetic chromatography (MEKC) and capillary gel electrophoresis (CGE). 

Calculations predicted heating rates of the order of millidegrees per second for the applied current using a field that would affect motion of particles with electrophoretic mobilities around 10 m V s [72]. Theoretical values of temperature-increase (predicted values) were calculated using buffers of known conductivity and compared with exact measurements. In 0.01 moll" phosphate buffer, kE = 3.6Sm (which is considered a high conductivity buffer for use in an electrophoretic instrument) a field of approximately 0.05 Vm" was applied [72]. The Joule-heating calculation with t in seconds is given by... 

The presence of surface conductance behind the slip plane alters the relationships between the various electrokinetic phenomena [83, 84] further complications arise in solvent mixtures [85]. Surface conductance can have a profound effect on the streaming current and electrophoretic mobility of polymer latices [86, 87]. In order to obtain an accurate interpretation of the electrostatic properties of a suspension, one must perform more than one type of electrokinetic experiment. One novel approach is to measure electrophoretic mobility and dielectric spectroscopy in a single instrument [88]. 

The need to develop new materials for electrophoretic analysis and macromolecular separations prompted by the needs of the human genome project and the rapidly advancing fields associated with biotechnology, advances in the development of new analytical instrumentation—especially capillary electrophoresis, and practical limitations of the media currently used for gel electrophoresis [73]... 

Saarinen, TR Woodward, WS, Computer-Controlled Pulsed Magnetic Field Gradient NMR System for Electrophoretic Mobility Measurements, Reviews of Scientific Instruments 59, 761, 1988. 

Electrophoretic methods of separation of LD Tsoenzymes have become routine in clinical laboratories. Efforts are now being made to standardize the methodologies used for LD isoenzymes, particularly by Rosalki (38). The preferred methods are based on electrophoresis on a solid medium, so that the several bands may be scanned instrumentally. Differential isoenzyme inhibition with urea or other inhibitors is based on the fact that the heart LD isoenzyme is more resistant to inhibition than other isoenzymes. However, the analyst then has the problem of allocating the observed degree of inhibition between the different isoenzymes of a given sample, a problem that has not been resolved satisfactorily thus far. Hence, differential inhibition is not as reliable for isoenzyme separation as is electrophoresis. 

Electrophoresis on cellulose acetate strips (Sepraphore III, Gelman Instrument, Ann Arbor, MI) was done in the conventional manner [12] in order to obtain a comparative electrophoretic mobility of non-adsorbed albumin. For this purpose, BSA-BSA (2.5 w/v) was deposited on the cellulose acetate paper twice in volumes of 10 ul each. Electrophoresis was attain performed in the Gelman Chamber with Pt electrodes at 20°C (see Table 3) After completion, the strips were stained with Ponceau S protein stain (Gelman Instruments) and washed with 5 acetic acid. The stained cellulose acid strips were subsequently cut into 3 mm wide pieces which were monitored for protein content y-count-ing. 

In the field of DNA sequencing instruments, Perkin-Elmer [26] switched from the PMT-based model 373 sequencer to the CCD-based model 377, which allowed the simultaneous discrimination of four or more colors in emission, in a single lane of an electrophoretic gel. The CCD made possible the use of a specific fluorescent label for each type of base and throughput was improved more than four times [27], Excitation uses an argon laser. 

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