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As an alternative to the use of hydraulic pressure, chromatographic mobile phases can be made to flow through a chromatographic column by the application of an electric field. As in capillary electrophoresis, this must be carried out in narrow bore capillaries. Thus, the instrumental requirements for electrochromatography are similar to those of free solution capillary electrophoresis.
 In CE it is often the case that the differences in electrophoretic mobilities of closely related chemical species are extremely small and as a result sufficient resolution may not be achieved despite the very high plate number. However, the use of packed capillaries introduces an additional separation mechanism, namely chromatographic partition. In electrochromatography the selectivity is therefore the result of a superimposition of electrophoretic and chromatographic migration. Thus, the various possibilities for modification of selectivities available to the HPLC user can be employed in electrochromatography.
With packed columns, unlike open tubes, UV-absorbance detection cannot be carried our through the capillary, at least not without severe difficulty, due to the presence of the packing material. In theory, packed columns could be connected to a short length of an open capillary in which the detection would take place. However, the problems, in terms of dead volumes etc., would arise in the joining of capillaries of only 50mm i.d. prohibit this approach.
Capital Analytical have developed a unique solution to this problem by producing capillaries with a small retaining frit inside the column positioned several centimetres from the capillary outlet. After packing the packed bed extends only as far as the retaining frit which allows detection to be carried out, using conventional capillary electrophoresis equipment, in the empty zone immediately following the frit. Using this method detection can be carried our with the absolute minimum extra-column broadening.
Packed Capillaries for Electrochromatography
The diagram below shows the arrangement of the on-column flow cell for Capital Analytical packed capillary columns.
 In the case of electrochromatography the observed chromatographic efficiency, in terms of the number of theoretical plates obtained, is often considerably greater than the same column driven at the same linear flow velocity using pressure induced flow. This is due to the ideal uniform flow characteristics of electro-osmotic flow.
In electrochromatography there is no direct relationship between the flow velocity and the particle diameter. Thus, the particle diameter can be reduced to well below the particle diameters currently used in HPLC. This leads to chromatographic efficiencies approaching those of free solution capillary electrophoresis. See chromatography below on 1.5µm diameter particles.
Packed Capillaries for Electrochromatography
Packed capillary columns for electrochromatography are available packed with any material from our vast range of HPLC packing material. These include: our own base deactivated OPTIMAL Inertpak and Optimal, Spherisil, Adsorbosphere, Apex, Chromegabond, Exsil, Hypersil, Kromasil Lichrosorb, Nucleosil, Partsil, Rosil (or C-Gel), Spherisorb, Synchropak, Techsphere, YMC and Zorbax.
Please contact us if the material you require is not listed.
The number of combinations of phase, particle size, and type of silica runs into several thousand. Thus, only a small selection of our range is listed below.
When ordering a packed capillary, please give a full specification of your requirements with your order.
Type |
Description |
Cat No. |
Price (£) |
|
Electrosil 1.5µm Particle Columns |
15-75cm x 75µm i.d. C18-Electrosil Packed Capillary 1.m |
EKTNGD5 |
|
Electrosil 1.m Particle Columns |
15-75cm x 5m i.d. C18-Electrosil Packed Capillary 1.5µm |
EKTNGD7 |
|
Spherisorb Columns |
15-75cm x 5m i.d. ODS1- Spherisorb Packed Capillary 3µm |
EKTBGD5 |
|
Spherisorb Columns |
15-75cm x 5m i.d. ODS2- Spherisorb Packed Capillary 3µm |
EKTBFD5 |
|
Spherisorb Columns |
15-75cm x 5m i.d. C8- Spherisorb Packed Capillary 3µm |
EKTBXD5 |
|
Spherisorb Columns |
15-75cm x 5m i.d. C6- Spherisorb Packed Capillary 3µm |
EKTBZD5 |
|
Spherisorb Columns |
15-75cm x 7m i.d. ODS1- Spherisorb Packed Capillary 3µm |
EKTBGD7 |
|
Spherisorb Columns |
15-75cm x 7m i.d. ODS2- Spherisorb Packed Capillary 3µm |
EKTBFD7 |
|
Spherisorb Columns |
15-75cm x 7m i.d. C8- Spherisorb Packed Capillary 3µm |
EKTBXD7 |
|
Spherisorb Columns |
15-75cm x 7m i.d. C6- Spherisorb Packed Capillary 3µm |
EKTBZD7 |
|
Hypersil Columns |
15-75cm x 50mm i.d. ODS- Hypersil Packed Capillary 3mm |
EKTAGD5 |
|
Hypersil Columns |
15-75cm x 50mm i.d. C8- Hypersil Packed Capillary 3mm |
EKTAFD5 |
|
Hypersil Columns |
15-75cm x 50mm i.d. C8 BDS-Hypersil Packed Capillary 3mm |
EKTAXD5 |
|
Hypersil Columns |
15-75cm x 50mm i.d. C18- Hypersil Packed Capillary 3mm |
EKTAZD5 |
|
Hypersil Columns |
15-75cm x 75mm i.d. ODS- Hypersil Packed Capillary 3mm |
EKTAGD7 |
|
Hypersil Columns |
15-75cm x 75mm i.d. C8- Hypersil Packed Capillary 3mm |
EKTAFD7 |
|
Hypersil Columns |
15-75cm x 75mm i.d. C8- BDS-Hypersil Packed Capillary 3mm |
EKTAXD7 |
|
Hypersil Columns |
15-75cm x 75mm i.d. C18- BDS-Hypersil Packed Capillary 3mm |
EKTAZD7 |
|
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