Columns are manufactured with a patented technology that provides a very reproducible packed column.
View Catalog Description of Milli-phase CEC Columns.

CE & CEC Product Index

• Efficiency
  150,000 to 400,000 plates/meter
• Selectivity
  Isocratic separations of neutral compounds possible
• Reproducible
  <2% RSD

Separation scientists are constantly looking for new technologies to assist them as they are continually challenged with smaller and smaller sample sizes and more and more difficult to separate samples. Capillary Electrophoresis (CE) provides much in the way of reduced sample requirements as injections sizes of 1 nano-liter are considered quite common. The efficiency that is part of (CE) can be as high as 1,000,000 plates per meter.

As scientists are presented with challenges that current technology do not satisfy, new techniques and hybrids are invented. Capillary Electro-chromatography (CEC) is a hybrid technology that combines the best of CE and micro-HPLC.

The high efficiency of CE is due to the “bulk flow” of buffers in a capillary when an electrical potential is applied across the capillary. Electro Osmotic Flow (EOF) is generated and has a unique “plug flow” which is what is responsible for the very high plate counts as compared to a pressure driven (HPLC) technology. See diagrams below.

CE is able to separate charged analytes based on their charge to mass ratios but is not very efficient at separating molecules of the same ratio or those which are uncharged. Micro-HPLC provides a great selectivity for most analytes that are presented to the scientist for separation. When micro-HPLC is used, a pressure driven technology, the parabolic flow of the mobile phase which reduces the efficiency. When working with very small samples, this becomes un-deisrable. Also, even in micro-HPLC, the injection sample requirement can be too high for many applications.

CEC uses the electric field advantages of CE (high efficiency) but utilizes columns that are familiar and similar (wide selectivity) to those used in HPLC and still requires very small sample size for injection. See graph below for comparison of CEC v. micro-HPLC.

CEC can be performed in any CE instrument that can provide pressure for injection once the columns have been properly conditioned and readied for use.

Resolution is increased in CEC over micro-HPLC due to the high efficiency of the technique. Also, due to the flow of CEC and that it is independent of channel spacing between particles in the CEC column, longer columns (up to 1M) containing very small particle sizes can be used without increase in back pressure normally found in HPLC. Theoretical plate counts can be significicantly increased over 400,000 per column in these cases as compared with typical HPLC column that will report approximately 25,000 plates per column.

High Speed is very common in CEC even when the particle size is as small as 1.5um by alleviating the need for longer columns. When using small columns such as 10cm, the separation can be Ultra-Fast with very high efficiency.

Low cost of solvents is also part of the CEC technique. Due the very small inner diameter, solvent flow is commonly 100nL/minute. This is about 10,000 times less solvent than that which is used in HPLC.

Using Electro-spray technology in Mass Spec, CEC columns are easily adapted. This further increases the versatility of CEC.

Milli-phase™ pre-packed CEC columns are manufactured using a patented electro-kinetic packing technique that provides excellent uniforminity from column to column which results in more reproducible results for you. Each and every column is packed with the packing material of your choice and is hand inspected under a microscope for uniformity. Each column is then tested on a CEC instrument and the actual test chromatogram is provided with the shipment. This chromatogram is proof that the column was packed properly and that flow was achieved and that a separation was performed. The column is evaluated for efficiency, selectivity and peak symmetry. If it does not meet our standards, it is rejected.

Both the inlet and the outlet frit are sintered inside the column using the packing materials. An optional detection can be provided by informing us at the time of order what instrument you have and where you would like the window. Detection windows can be created by the end user as well. Many customers do not order a window since they are using the column with a Mass Spec instrument and detection windows are not needed.

The columns are flexible and can be bent since they are coated with polyimide but the detection window is very fragile and must be handled with extreme care. Once you receive the column you must follow our procedure for column conditioning to remove any air bubbles that may have developed. Click here to view procedure on How to Condition a CEC Column.

To condition a CEC column the user must force a solvent through the column to assure that a current can be produced when the voltage is applied. If there are any dry spots or air bubbles, the current will stop and so will the EOF. The user therefore must assure that there are not air bubbles or dry spots. To accomplish this you must apply pressure using a syringe and pushing the solvent through the column to assure that it is saturated. It is inconvenient for a technician to take the time to manually apply the pressure since the CE instruments do not provide sufficient pressure to do this and we thus recommend that the MicroSolv CEC Hand Pump be used. You can apply pressure to the column by turning the head screw of the Hand Pump. You can then leave the column to be saturated and return to it once every fifteen minutes or so.