 Column Care |
| Proper column care and use will enhance application success of GC column and prolong column lifetime. Column care includes how to install it, how to maintain it for storage, and how to regenerate its performance. |
| Column installation |
 Pre-installation |
1.Know your GC
，GC condition: brand new or well used
，Recent change of GC location
，GC idling duration
，Recent maintenance of GC system and gas line change
，Abnormal GC column degradation
，Previous GC column performance record/logbook
，Carrier gas quality
All these offer clues about instrument system performance for new use. Particularly, if previous GC column behaved abnormally, such as shortened lifetime, high bleed, ghost peak, peaking tailing, no signal or too high baseline signal, most likely, it pinpoints leaking problem, dirty inlet, gas flow or blockage of detector jet.
2.Have a good GC ready
If your GC exhibits some of above symptoms, fix instrument problems by following GC manufacturer¨s recommendations. Some of the recommendations are: |
Use high purity gases including column carrier gas and makeup gas
Setup proper gas flows for both inlet and detector
Change seals, septum and liner
Change column ferrules
Change jet
Condition GC inlet and detector at high temperature for hours |
|
After checking out these practices, you will have a good GC ready for new instrumentation with your new GC column.
3.Know your GC column |
Brand new column or used column
Column shelf time in lab
Any column breakage
Copy of test chromatogram from column manufacturer
Previous analysis chromatogram of the column to be used |
|
| It is obvious that you won¨t waste your time to install a bad column. |
| |
Installation
1.Carefully uncoil column one half coils on both ends
2.Loosely hang the column inside GC oven
3.Use known good and correct ferrules and column nuts
4.Install the column nuts and ferrules to column each end
5.Cut column each end neatly for 3！5cm with a good column cutter. Do not hand break column end tip without a cutter
6.Thoroughly examine the cut. Re-cut column if the cut is not neat
7.Attach column end to inlet. Follow instrument manufacturer¨s specification on column end tip length into
instrument, such as 2-3cm for split/split inlet, 1-2mm gap length from the very end of the FID jet, etc. Make sure the
column end not touch metal wall more than 3 times, as multiple touching may damage the column tips that affect
sample introduction into column
8.Finger-tighten the column nut with another hand holding column end position for proper insert length, then use
proper size wrench to completely tighten the nuts. Do not over tighten the nut, as it may smash the column. Make
sure column tip insert length is in the range of GC manufacturer¨s recommendation or specification
9.Stepwise setup the column pressure to establish column flow or set up proper column flow
10.Repeat connection to detector
11.Securely hang the column inside GC oven. Do not over uncoil GC column at each end as it may become broken
after thermal cycling. Coil extra loosed column into the column cage for securing
12.Adjust column flow to manufacturer¨s specification. A general flow setting would be: |
Column id (mm)
|
Column flow range (ml/min) |
0.53
|
5！8 |
0.32
|
1.0！2.5 |
0.25
|
0.8！1.5 |
| 0.2 |
0.4！1.0 |
|
13.Check for any leak sign with Snoop technique or other proper leak detection technique
14.Set properly inlet and detector temperatures
15.Set oven temperature around 50！100≧
16.Turn on detector after both the temperature and the flows have been established
17.Check for stabilized signal level. If signal is too low or too high, it may indicate leaking column connection or
broken column at connection ends. Redo the column installation as needed
18.Condition columns at its upper limit temperature - (10！20≧) for minimum 30min. Over night conditioning is
preferred
19.Check for detector signal. If it is too high, there may be a leaking problem, dirty inlet/detector, or bad column. Find
leaking place and redo column installation, or clean inlet/detector, or change another column
20.Adjust column flow to analysis condition if necessary
Good column installation will help obtaining good and successful analysis results. |
| |
| Column Storage |
Idling inside GC oven
Maintain proper oven temperature, e.g., 100！150≧ under proper column carrier flow.
Out side GC oven
Septum-seal both ends of the column, store column in its original box. Avoid moisture or chemical vapor.
Causes of performance degradation
Many root causes can result in column performance degradation. Most root causes are oxygen present in carrier gas stream (oxidation), thermal damage, and sample contamination. Check for instrumentation obvious before time-consuming troubleshooting. The following table gives out a general troubleshooting process and some remedies. It is important to follow proper column installation step and maintain a good instrument to prevent from column performance degradation during run time. |
 |
| |
|
| Column regeneration |
| Conditioning |
| Condition or bake column at isothermal temperature close to the column upper temperature limit with 2x column working carrier flow for 2！24hours. Avoid use programmable temperature profile to condition column. This regeneration can be effective for sample contamination. But sometimes conditioning can result in accelerated degradation if oxygen is presented in carrier stream. Column surface may become active for many polar compounds after conditioning. |
| |
| Multiple solvent injections |
| Injecting solvent multiple times into columns at 50！100≧ oven temperature may regenerate column performance. Avoid using oven temperature below solvent boiling point as solvent condensation will wash out too much stationary phase at the inlet end. The column surface may become less inert or more active after multiple time injections. |
Trim both ends of column
Trim both ends of column by 0.1！1m could be an easy and effective way to regenerate column performance. Trim longer length at detector end than at inlet end. Adjust instrument condition (e.g., column flow) accordingly to maintain retention time locking. After trimming, condition column for 30min to 2hrs.
Trim column leads to shorter column length, and eventually, make it unusable.
Solvent rinse
Offline solvent rinse is an old fashion to regenerate column performance. As column becomes commodity product now days, we do not recommend this technique. Instead, we recommend solvent injection as an alternate.
In extreme case of offline solvent rinse needed, use high grade (HPLC or GC grade) solvent compatible to stationary phase, such as non-aqueous solvent for wax column, hexane/toluene for polysiloxane column. Column should only be rinsed with 2！3 column volume solvent at low pressure. Avoid rapidly pressure change that often causes column breakage. Gas purge dry column for 30min to one hour, and properly condition the column at its upper temperature limit for 2！10hours. |
|
|
