Electrophoresis commercial instruments

Since all electrophoretic mobility values are proportional to the reciprocal viscosity of the buffer, as derived in Chapter 1, the experimental mobility values n must be normalized to the same buffer viscosity to eliminate all other influences on the experimental data besides the association equilibrium. Some commercial capillary zone electrophoresis (CZE) instruments allow the application of a constant pressure to the capillary. With such an instrument the viscosity of the buffer can be determined by injecting a neutral marker into the buffer and then calculating the viscosity from the time that the marker needs to travel through the capillary at a set pressure. During this experiment the high voltage is switched off. 

It has been over a decade since the first commercial capillary electrophoresis (CE) instrument was introduced and its strengths and weaknesses identified. Its outstanding resolving ability and high efficiencies were praised. However, the instrument s robustness was less than desirable. Since then, manufacturers have addressed these concerns and have made refinements to the commercial system such that ruggedness and reproducibility have improved significantly. 

Several instruments have been developed in various laboratories since the late 1970s. Currently, several companies have introduced the capillary electrophoresis commercially (for example Microphoretic Systems, Sunnyvale, California Bio-Rad, Richmond, California Applied Biosystems, Inc., Foster City, California and Beckman Instruments, Inc., Palo Alto, California). Although the instruments have many practical features for the separation and analysis of analytes, several new features need to be incorporated (for routine use) by protein chemists. 

Many commercial instruments are available for scanning stained electrophoresis strips. One of these (V2) operates at high speed and includes automatic zero adjustment, digital readout of the protein fractions and displays the electrophoretic pattern as a tracing on the fluorescent screen of a cathode ray tube. 

The increase in temperature during a separation is observed to be due to Joule heating Ideally, the retention factor, k, should be independent of the applied voltage or current, but, actually, k does depend on the applied voltage. Although the temperature of the separation capillary is controlled with a Uquid coolant or a drculating airstream in most commercially available capillary electrophoresis (CE) instruments, the retention factor usually deaeases, almost linearly, with an increase in the velocity of the EOF or an increase in the current. However, the dependence is much less than that observed in a CE system without forced-cooling apparatus. 

Altria, K. D. High-speed determination of drug related impurities by capillary electrophoresis employing commercial instrumentation.. Chromatogr. 636 125-132, 1993. 

In contrast to the cumbersome and time-consuming tasks of conventional electrophoresis, CE is well suited to automation. Samples are easily applied to the capillary, a variety of detector types can be used, and the resulting electrophore-tograms can be analyzed and manipulated in much the same manner as chromatograms. Commercial instruments resemble many HPLC instruments in terms of automated sample loading and data analysis. Traditional serum protein electrophoresis, for example, can be fully automated with CE. 

We developed an ICP time-of-flight mass spectrometer, which is now a commercial instrument. We also have a new device, a double-focusing mass spectrometer with a detector array, to look at many different elements at the same time. The third new type of mass spectrometer geometry is a time-of-flight instrument that uses two ion sources at the same time. One third of proteins contain metal atoms, and we hope to separate the proteins by capillary electrophoresis, then use this spectrometer to characterize the proteins and measure their metal atoms at the same time. 

Nowadays, the use of commercial instruments prevails, and studies using home-made machines are rare. The tables in Chapter 3 (with the literature search having been completed in 2007) report results obtained by the following commercial instruments based on electrophoresis, in which the mobility is calculated from the velocity of colloidal particles ... 

Home-made electrophoresis machines have been designed for special applications that are beyond the operational range of commercial instruments. A high-temperature electrophoresis apparatuses is described in [259-262]. Illustrations of home-made apparatuses for measurements of the electrophoretic mobility of gas bubbles can be found in [263,264]. 

On the contrary to rod shaped gels, slab gels can be dried on a paper sheet after staining and destaining and stored in this rather conventional form. Commercial instruments for slab gel electrophoresis and the destaining accessories can be obtained from e.g., Pharmacia Fine Chemicals, Uppsala, Sweden Desaga, Heidelberg, FRG or Bio-Rad Laboratories, Richmond, CA, USA. 

Examining the theory for electrophoresis reveals that high voltages and small separation lengths are two strategies primarily involved in ultrafast separations, for both capillary and microfluidic formats. However, most commercial instruments are incompatible with short separation distances and are not equipped with the fast injection devices and sensitive detectors needed for rapid separations. Therefore, methods development for both ultrafast capillary and microfluidic separations has gone hand-in-hand with instrument development. Instrument development has focused on methods to maximize voltages, minimize injection volumes, detect small amounts of analyte, and automate data analysis. 

In CZE, serum proteins have been separated using different buffers (e.g., Tris and Tricine), but mostly borate, with pH of 8-11 [22,25-29]. Serum protein separation can be completed by CE in about 2-10 min in contrast to 1-2 h for agarose electrophoresis (AG) (Figure 26.1). The correlation coefficient between CE and AG for the separated bands is good [30-32]. Some commercial instruments use multicapillaries of narrow diameter (25 p.m) to increase the throughput of the analysis. The narrow capillaries produce better resolution than the wider capillaries with a much shorter migration time [28]. This is true for all CE separations. 

Wang GR, Sas I, Jiang H, Janzen WP, Hodge CN (2008) Photobleaching-based flow measurement in a commercial capillary electrophoresis chip instrument. Electrophoresis 29(6) 1253-1263... 

Particle electrophoresis, also sometimes known as microscope electrophoresis or microelectrophoresis, is one of the easiest and most useful techniques for investigating the electrical properties of colloidal particles. If the system of interest is in the form of a reasonably stable dispersion of particle size observable by light microscopy (say, larger than 200 nm for practical application), the electrokinetic behavior of the system can be observed and measured directly. Several commercial instruments are available for the purpose. For smaller particles, laser scattering instruments are now readily available. 

Capillary electrophoresis is a relatively new technique. It was suggested in 1976, and first published in 1979. Commercial instruments became available in 1988, and the... 

As useful as conventional slab electrophoresis is, this type of electrophoretic separation is typically slow, labor intensive, and difficult to automate. Slab electrophoresis does not yield very precise quantitative information. During the mid-to-late 1980s, there was explosive growth in research and application of electrophoresis performed in capillary tubes, and several commercial instruments appeared. Capillary electrophoresis (CE) yields high-speed, high-resolution separations on exceptionally small sample volumes (0.1 to 10 nL in contrast to slab electrophoresis, which requires samples in the pL range). Additionally, the separated... 

---