Packed versus capillary column

[atiqah_ms]

Dear All,

I have some doubt regarding the performance of both type of column

If I have a method indicate that the column use is a glass packed column with stationary phase 5% polymethylphenylsiloxane, (1.8m x 3mm internal diameter)

Can I use a capillary column with the same stationary phase? different length and internal diameter.

Does it effect the chromatogram peak? (Afraid no peak appear)

and similar to the detector.. If the method mention to use MS..Is it ok if I use GC-FID (Got FID only in my lab )

Hope to hear some feedback


Thanks
Sofia

[CE Instruments]

Yes, yes, yes. However this may not answer your question. Without the details of your application how can anyone be certain ?

Perhaps you would have been better to ask if the kit you have is suitable for the application ? Are you subject to any external regulation (FDA, IP, ??) that might further restrict the method you can use ?

[chromatographer1]

It is quite unlikely that you would have a packed column Mass Spec method, unless it is decades old. Capillary columns were used extensively during the 1970s-1980s and replaced most packed columns after those years.

You have a fairly low retentive 5% Phenyl silicone packed column. Generally a 0.32 to 0.53mm ID capillary with a 0.5 micron phase thickness is comparable.

The amount of sample that can be injected is much less with the capillary column. But if you can use a MS then the low levels that can be detected compensates for this fact.

If the method you seek to replace uses a MS and all you have is a FID, then it is likely that you will NOT be able to perform the method with a FID.

If you could share a few more details (is this a secret project?) perhaps the Forum members could offer you more applicable advice.

best wishes,

Rod

[atiqah_ms]

Hi everybody,

Actually I am interested to separate chlorocresol from FP (suspension)
Below is the method for as according to BP 2012

Test solution: 1gm chloro in 100ml acetone,
Ref. sol: 1ml test solution in 100ml acetone, dilute 5 ml in 100ml acetone

column: glass packed column (1.8m x 3-4mm internal diameter)
stationary phase: silanised diatomaceous earth for GC impregnated with 3-5% m/m polymethylphenylsiloxane R
Flow rate: 30ml/min
detector : FID
carrier gas: N2
Detector:230, injector: 210, column:125

My doubt is..

May chloro peak appear if I change the column to capillary column with 5% polymethylphenylsiloxane?

(The cost for packed column is expensive rather than cap column...)

[Peter Apps]

There is no particular reason why you will not see a peak for chlorocresol on a capillary column -in fact you may see a peak for each isomer. Expect some tailing due to adsorption. To locate which peak is the chlorocresol you will need a standard of the pure substance(s) so you can easily verify whether a peak is detectable by running a standard before you try running samples.

If you can, use a solvent other than acetone, whcih is reputed to be bad for siloxane phases.

Peter

[chromatographer1]

OK,

suspension. Now the truth comes to the top. You can mess up (contaminate beyond usefulness) a capillary column with only a few injections of *junk*. Packed columns tolerate much more abuse and are much cheaper to replace when contaminated. The expense you mention is due to the non-standand column size you referenced. 4mm ID is a more appropriate ID for the glass column. A 2mm is another choice to keep costs down. Avoid 3mm ID columns. I would expect a packed column to cost less than $150. You could use a short megabore column to approximate the performance of the packed column (Buy a 30 meter and cut it into 2 or 3 columns).

You are probably aware that HPLC might be a better solution, especially if you have a lot of samples.

Be mindful that a dirty injection liner can absorb a lot of cresols. They might never get to the column. For clean samples the capillary will give you a lower LOD and better peak shapes.

Good luck,

Rod