CP PoraBond Q - Poor Tailing Factor

[Phil Leigh]

Dear colleagues,

I have run ethanol determinations from an aqueous solution containing polysorbate 80 for several years without problems. During the past year, the Tailing Factors for ethanol and propan-1-ol (internal standard) are highly variable throughout the run and often >>1.5 (in-house limit), sometimes >2.0 Also, peak areas can be highly erratic.

Conditions:

Column 25m x 0.32mm x 5um
Col T = 150C
Inj T = 150C
Det T = 240C
Carrier gas Helium
Flow 1ml/min
Split 1:50
Injection volume 1uL or 0.5uL (depending on application)

I have recently adopted a policy of regular cleaning of the split liner and am using a liner with a 'cup' near the base without silanised glass wool.

I have also cut about 20cm from the inlet end of the column.

The chromatography has improved slightly but is still not as good as it used to be.

Any suggestions for further improvement?

Regards,

[chromatographer1]

The pores of the polymer may be contaminated (filled) with debris, especially at the head of the column.

Cut 1 to 5 meters off the front of the column and see if that helps. A replaceable pre-column helps with non-volatile components in your testing solution.

best wishes,

Rodney George

[Phil Leigh]

Thanks Rodney,

I'll be less conservative and cut off a longer length of tubing from the inlet. Other sources have advised an increase in injector temperature to ~250C (presently 150C). However, Im limited by regulatory requirement to +/-10% changes in temperature.

Regards,

[Phil Leigh]

Thanks Rodney,

I'll be less conservative and cut off a longer length of tubing from the inlet. Other sources have advised an increase in injector temperature to ~250C (presently 150C). However, Im limited by regulatory requirement to +/-10% changes in temperature.

Regards,