Handling, cutting and cleaning bare fused silica tubing for CE
Simplus™ brand capillaries are clad in polyimide coating. This allows the user to handle them in a manner that is very similar to that of optical fibers.
Great Care must be exercised when using internal pressure and Simplus™ brand capillary or column. Although they are very robust, a small particle or a minute chemical etching can create the sight for an internal stress crack. The combination of pressure and heat may even create more concern. Environmental or chemical exposure in the capillary or column can cause failure.
Bare Fused Silica Bending Stress
10 + 25m are supplied
on a convenient spool
Strength of the capillary tubing or the column tubing can be affected by chemical modification in the capillary or by being exposed to the elements. Care should be exercised in bending the capillaries and columns. The following table shows bending radius for typical MicroSolvCE Capillaries and CEC Columns.
Bending Stress for Simplus™ Brand Capillaries and Columns
OD 365um Tubing
Bend Radius (mm)
|Applied Bending Stress (kpsi)
Flow Rates in Capillaries
Keeping in mind the Bernoulli Principle, it is important to remember that when a viscous liquid flows through a pipe, the speed of the liquid at the center of the pipe is greater than near the walls due to friction and other factors. This resistance to flow can be written as:
As the resistance to flow is inversely proportional to the square of the radius (ID), a change from 100mm to 50mm means a four-fold resistance to flow and a subsequent difference in flow rate.
Trace Elements in Simplus™ Brand Bare Fused Silica Capillaries
|0 to 0.01
|0 to 0.05
|0 to 0.1 (0.0005)
|0 to 0.01
|0.01 to 0.1
|0 to 0.001 (0.01)
|0 to 0.1 (0.05)
|0 to o.001
Connectors & Coupling Simplus™ Brand Silica Capillaries
Couplers and connectors are available for all sizes of capillaries. It is recommended that if you are coupling two capillaries or two columns that you use a fused silica connector since the thermal expansions will match. If metal connectors are used, contamination of the solutes and buffers may ensue as well as leaks.
Fluorescence in Simplus™ Brand Silica Capillaries
Fused Silica can exhibit fluorescence when illuminated at 254nm. Not all fused silica capillaries will exhibit this. MicroSolvCE capillaries are very low in fluorescence. MicroSolvCE bare fused silica capillaries are free from visible fluorescence at wavelengths greater than 290nm.
Removing Polyimide from Simplus™ Brand Capillaries and Columns
Open Flame: Open flames in laboratories are usually not considered good laboratory practice unless it is performed in an explosion proof fume hood. Open flames can make the glass brittle and is not the best technique. It will remove the polyimide. This method is not recommended for any CE or CEC column.
Gas Torch: For the same reasons that any open flame (see above) is not recommended, using a Gas Torch may be considered dangerous and you should check with your institution’s policies before using this technique. If you use oxygen/hydrogen flame, it will perform satisfactorily and not leave the glass weak. This method is not recommended for any CE or CEC column.
Oven: This method is only recommended for removing large sections of polyimide from bare fused silica and not with any coated column. Temperatures greater than 600ºC will flake off the polyimide and not affect the glass. This will take up to one hour to accomplish.
Electric Coil Heater: This is a very convenient and fast way to remove small amounts of polyimide for creating detection windows in bare fused silica and some coated CE and CEC columns. It is important not to touch the surface of the heating coils during heating or the glass can become weakened and brittle.
Electric Arc: This technique works very well on bare fused silica and is not recommended for use on coated columns. This technique works very well and the glass remains very strong.
CO2 Lasers: This is the best method for making windows that leave the glass strong and untouched. One must have a CO2 laser to accomplish this. This can be used on bare fused silica and some coated columns.
Sulfuric Acid: This technique works very well on all MicroSolvCE bare fused silica capillaries and coated columns. The glass is not affected and the polyimide is removed very quickly. The sulfuric acid must be heated to over 100ºC. This can be very dangerous and you should check with your institution’s laboratory safety procedures before using this.
Strong Bases: This will remove the polyimide but it will also damage the glass. This is NOT recommended.
Wire Strippers: This method is not recommended since it will damage the glass.