Handling & Use of PicoFrit Columns

There are some important considerations in the handling and use of PicoFrit® columns that make them very different from other chromatography columns. PicoFrit columns are fabricated from 360 µm OD, polyimide-coated, fused-silica tubing, as shown in below. One end of the column, referred to as the "tip end," has a specially tapered tip with an integral high-porosity frit. Behind the frit is the packed chromatography bed. There is no frit at the back end of the bed, only unpacked fused-silica tubing. Mobile phase flow must always be directed toward the tip. Reversing the flow may result in partial or complete unpacking of the chromatographybed.

PicoFrit column illustrated

The PicoFrit column is packaged as a loop, with the tip and distal ends protected by a sleeve of snug-fitting FEP (Teflon®) clear tubing. This sleeve keeps both ends of the column at the same pressure during shipping and storage. The loop should not be opened until the column is being prepared for installation and conditioning. Note the label attached to the orange PEEK™ sleeve that slides along the length of the column. The arrow on the label points toward the tip end and indicates the direction of flow. Columns are shipped filled with methanol and need to be conditioned with appropriate mobile phase for your gradient. Finally, since there is no distal frit, the distal end of the column bed may loosen with time. The bed will repack when the column is pressurized.

Removing and Opening PicoFrit Columns

As an extra precaution against tip damage, leave the FEPsleeve in place over the tip end during initial column conditioningand handling. Remove it from the tip end immediately before mountingthe column on the mass spectrometer.

The inlet end of the PicoFrit column is unfritted. As a result, some unsettling of the chromatography bed can occur along the length of the column tubing during shipping and handling. Always pressurize and condition your column prior to cleaving the tubing to it's final length to avoid loss of the chromatography bed into the waste tubing. See Technical Note FS-1 on how to cleave fused-silica tubing for LC-MS.

  1. Care must be taken when removing the column from the FEP sleeve to prevent damaging the fragile tip and frit.
  2. Do not bend the FEP sleeve while the tip is inside. The free- sliding PEEK™ sleeve will be used to push the FEP sleeve off the fused-silica tubing without damaging the tip.
  3. Remove the distal end of the column from the FEP sleeve by either pulling it free of the sleeve or, preferably, by cleaving the fused-silica tubing near the terminus.
  4. Slide the PEEK sleeve toward the tip end until it butts up against the FEP sleeve.
  5. Orient the FEP sleeve vertically, with the tip facing the floor. This way, when the FEP sleeve slides free, it will fall to the ground without damaging the tip.
  6. Push the PEEK sleeve against the FEP sleeve until the FEP sleeve falls off. This may take a bit of force; do not be afraid to push hard. You will have to move the PEEK sleeve 3–5 mm. Do not let the PEEK sleeve slide off the tip end. Instead, remove it by sliding it over the distal or back end of the column.

Storing PicoFrit Columns

There are two methods for storing PicoFit columns. For short term storage, the column tip should be protected using a standard PEEK union and submerged in a vial of solvent. This method can be used safely for a few weeks and up to 2 months. However, long-term storage in methanol and other solvents can cause swelling of the polyimide coating of the tubing, which can affect performance-even causing it to slough off. For long-term storage, remove the column from the box and hang the loop vertically, with the FEP sleeve nearest to the floor. Column reconditioining will most likely be required prior to use.

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