Frequently Asked Questions: Packed & Micropacked Columns
- How do I order a packed GC column?
- Can you recommend an equivalent capillary column for a particular packed column?
- I would like a 4 mm ID glass packed column, but you do not offer glass packed columns. What do you recommend?
- How do I install a packed column into a capillary GC injection port?
- How do I convert my instrument’s packed-column injector to accept fused silica capillary columns?
- How do I install a micropacked column?
- How do I condition a new packed or micropacked column?
If your question doesn’t appear on the list, please contact Restek’s expert chemists. (Remember to include your company name and complete mailing address.)
How do I order a packed GC column?
Browse our selection of stock packed columns. If you don't see what you need, complete our Custom Packed Column Form. After receiving this detailed configuration information, we will quickly reply with price and delivery information.
Can you recommend an equivalent capillary column for a particular packed column?
Availability of a capillary equivalent to a given packed column depends on a number of variables. Some packed columns are similar to existing capillaries, but others have no direct equivalent. The USP Cross Reference Chart in the Packed Columns section of our general catalog is a good resource for these conversions.
I would like a 4 mm ID glass packed column, but you do not offer glass packed columns. What do you recommend?
Depending on what method or protocol you are following, you likely can use our passivated stainless steel columns, made with SilcoSmooth tubing. These columns combine the flexibility and durability of stainless steel with the inertness of fused silica. A 3.1 mm ID (3/16" OD) SilcoSmooth column will offer very comparable performance to a 4 mm ID glass column, without the hazard of breakage. So, if your method does not specify glass, SilcoSmooth tubing is an excellent alternative.
How do I install a packed column into a capillary GC injection port?
The easiest way to install a packed column into a capillary column injection port is to use a “pigtail” set-up. All that is needed is a short piece of deactivated 0.53 mm ID MXT guard column tubing (which can be cut from cat.# 70045), appropriate compression unions (reducing or straight-through) and appropriate ferrules. For example, for 1/8" packed columns, reducing union 23168 along with ferrules 20202 (for the 0.53 mm ID MXT column segment) is all that is needed. The same setup can usually be used for the detector side as well.
How do I convert my instrument’s packed column injector to accept fused silica capillary columns?
Two types of inlet conversion kits adapt a 1/4" packed column injection port to accept fused silica capillary columns: the Vu-Tight liner and the Uniliner liner with sleeve adaptor. The Vu-Tight liner fits into the injection port and allows visual confirmation of the connection between the column and the liner. The Uniliner liner and sleeve adaptor allow either direct or on-column injection when using fused silica capillary columns. Both systems incorporate a Press-Tight connection between the liner and the column inlet, minimize dead volume, and reduce solvent peak tailing. Complete product descriptions and instrument compatibility information are given in our catalog.
How do I install a micropacked column?
To install into a capillary column injection port:
If the column tubing is too large to install through the current capillary column nut, you can use a “pig-tail” setup with a 1/16” compression union like cat.# 23165. Simply connect a short piece of MXT tubing (cut from cat.# 70045) into one end of the union with ferrule 20202, and use ferrule 21058 to install a 0.95 mm OD micropacked column into the other end of the union. Or for 1/16” OD columns, use the stainless-steel compression ferrules (which come with the compression union) to install into the opposite end of the union. The MXT tubing should fit through most capillary column nuts. We may have an appropriate kit for Agilent GCs to make installation easier.
To install into a packed-column injection port:
Check your instrument manual for instructions. For Agilent instruments, you may be able to use an injection port adaptor fitting like cat.# 21303 with an appropriate liner like cat.# 20967. For 0.95 mm OD columns, you will need ferrules 21058; for 1/16” OD columns, you can either use the stainless steel compression ferrule that is included with adaptor cat.# 21303 or 1/16" graphite compression ferrules like cat.# 20207 or cat.# 21060.
How do I condition a new packed or micropacked column?
The following steps will ensure that your packed or micropacked column is ready to use just a few hours after installation. Be sure to use only dry (no moisture) high-purity carrier gas to condition your column. In addition, quality gas traps are strongly recommended.
Cool all heated zones in your GC, and then turn off all GC gases. If a column is installed, allow both the column and the instrument to depressurize before proceeding.
Caution: Removing a packed or micropacked column from the GC (or more specifically, the inlet) before it depressurizes can cause a pressure surge capable of expelling packing from the column. Depressurizing before all heated zones in your GC are cool can also damage your column.
Install your new packed or micropacked column into the injection port. Do not connect the column to the detector at this time; instead, cap the detector. Do not turn on any heated zones.
Slowly increase the head-pressure just until carrier gas flow starts exiting from the column.
Attach an electronic flow meter (or soap-bubble flow meter) to the outlet of the column and once again begin to slowly increase the head-pressure. When the desired column flow rate has been obtained (see Table I for common column conditioning flow rates) continue to monitor the exiting carrier gas flow rate for five minutes to make sure it is stable.
Warning: If you are using hydrogen as your carrier gas, you must either safely vent the open end of your column out of the oven to prevent hydrogen buildup, or safely vent the hydrogen gas from a non-destructive detector (like a TCD) in order to minimize the potential of an explosion. If using a destructive detector like a FID, make sure the flame is lit. Note: never connect a flowmeter to a lit FID or a heated detector.
Disconnect the flowmeter, and purge the column for an additional ten minutes to remove all traces of air. Set the GC oven temperature to 100 °C. Heat the GC injection port (if applicable) to the desired temperature, but do not expose the column to higher temperatures than the maximum temperature of the column. Program the oven to ramp at 5 °C/min to 20 °C below the column’s maximum temperature, and begin heating GC oven. When the appropriate temperature is reached (20 °C below the column’s maximum temperature), hold at this temperature for one hour (except for the packings listed below).
For solid supports with liquid phase loadings >10%: Hold for two hours.
For molecular sieves: Hold for three hours. (Conditioning with high-purity dry nitrogen is also recommended.)
Cool the GC oven, but do not turn off the carrier gas. Install the column into the detector. Heat the detector to the desired temperature, but do not expose the column to higher temperatures than the maximum temperature of the column.
Your column is conditioned and ready to use.
Never perform GC maintenance (even just replacing a septum or liner) and never remove a packed or micropacked column from the GC without A) cooling all heated zones in your GC, B) turning all GC gases off, and C) allowing both the column and the instrument to depressurize. If you fail to do these things, the column’s bed may collapse, particles may be expelled from the column, or the column may be otherwise damaged.
If the column will not be used for more than one week, the column should be cooled and the carrier gas turned off. If the carrier gas is left on, make sure the oven remains set to 100 °C to keep moisture (water) from condensing inside the column.
A micropacked column (0.53 mm ID through 1 mm ID) should work well with high-sensitivity detectors like HID, DID, FID, etc. However, when using a low-sensitivity detector like a TCD, consider using a 2 mm ID (1/8” OD) packed column for higher capacity.
Table I: Common conditioning carrier gas flow rates for packed and micropacked columns.
|Column Dimensions||Flow Rate|
|0.53 mm ID (0.74 mm OD)||5 mL/min|
|0.75 mm ID (0.95 mm OD)||7.5 mL/min|
|1 mm ID (1/16” OD)||10 mL/min|
|2 mm ID (1/8” OD)||20 mL/min|
|3.1 mm ID (3/16” OD)||30 mL/min|