Glass Packed Columns

[Jumpshooter]

Like most of the chrom forum writers I am from exclusively a "capillary" column world. We are investigating a referred method for phenolics that calls for a 1/4 diameter, 6 ft long Glass Column Packed. Anyone here know anything about the comparative flow rates of carrier gas, or oven parameters for such columns? Our commonly used flow rates for capillary work are 8 psig, and 100C_ramp 10C/min_to maximum of 285C_hold 1 min. Are Glass packed cols similar or dissimilar?
Upper management wants to try this glass col method so the impetus for doing this rather than capillaries is implied

[chromatographer1]

Using helium carrier the average optimum flow rate for 0.25mm ID columns is around 21cm per sec for an unretained peak.

For packed columns the optimum flow rate is about 20 cc/min flow rate for 2mm ID column and 60-80 cc/min for 4mm ID columns. (Flow rate will vary with a set pressure depending upon the kind of packing support, the liquid phase with which it is coated, and the 'tightness' of the packing within the column.

Temperature limits are generally lower for packed columns as the phases are not chemically bonded to the support for most phases.

Capillary columns are generally more inert and can see analytes that might be absorbed on a packed column, but conversely, a packed column can take more sample and thus may be able to see smaller amounts of an analyte within a sample. It all depends upon the samples and the analytes involved. There is no simple straightforward answer.

Also be remember that phases for capillaries are limited in their availability. For example, polyester phases are generally not available.

I suggest you contact the major capillary column manufacturers and see if they have an alternative method using capillaries for the packed column procedure you wish to follow.

Use their technical service phone numbers or use the internet to contact them. Or if you wish since I live in Kansas City give me an email and I will meet you for coffee and discuss.

best wishes,

Rodney George
consultant USA

[Jumpshooter]

Thanks for your kind and timely response Chrom #1; I shall re-read this good info and possibly arrange to meet with you soon. Glad you're local!

[GaryR]

Also be aware that there may be some hardware issues.
For capillary columns you usually have split/splitless inlets (I am mainly familiar with the Agilent 6890s). These inlets will not take a glass packed column. for this you would need a purge/packed inlet. This is a major hardware change.
And, if using FID you may need to change jets, which is quite easy.

[Jumpshooter]

I have installed the glass packed column onto inlet A (non split/splitless side).
I am not clear of why there would be a need to install a different type of JET onto our FID as a result of swithing from the capillary col.?

DOes the Detector have a problem lighting up when using the glass col?
Why does gently blowing breath on it caue the glowplug to ignite the DET? When it did not light under its own normal operation mode?

[Consumer Products Guy]

Upper management wants to try this glass col method so the impetus for doing this rather than capillaries is implied :wink:

Does upper management want your results reported on clay tablets as well ?

Packed columns do not require FID make-up gas or inlet splitting. Usually the FID is changed to a packed-column type. I do have one 1/8 inch packed column in a split/splitless inlet on a 5890 GC, I use a stainless steel liner and have the vent and septum purge lines capped off. It does work. I hacksawed off an Agilent nut that normally would hold the gold seal under the inlet, and use a vespel ferrule there to hold the column securely so I don't rely solely on the upper O-ring (around the 1/4 inch SS liner) to hold the column in. I attach the column to that linder before installing, but you may not be able to do that with a 1/4 inch glass column. You also need to be careful with torque so as not to break that glass column when tightening, depends on ferrule type you use. There used to be special torque wrenches available for these, but packed columns are in very limited use these days.

[Jumpshooter]

I appreciate all of the kind sharing of ''tribal knowledge", I will install and get this column up and running.
It was manufactured as a "front to front" orientation with the injector side about 5 inches longer than the detector side of the glass col. it was delivered with two nuts and 4 ferrules.
I fear that I'd best be careful about tightening it --else I fracture the glass

[chromatographer1]

If you got graphite ferrules (I hope so) tighten only until the first gentle resistance is encountered.

IF you got the harder impregnated ferrules then great care must be taken not to break the column. 1/8 turn past snug is quite enough. Perhaps you might practice on a spare piece of glass tubing before you attempt installing the column. It will be worth your while.

best wishes,

Rodney George
consultant USA

[AICMM]

Jumpshooter,

You can always use a piece of megabore to connect from inlet to column or outlet to column. You will lose a little bit of resolution, but hey, you are using 1/4" packed. By the way, I do not believe you will have great phenol stability over the long haul (based on my experience with phenols by packed many years ago...) The other important thing about glass tubing is to make sure you do not run it all the into the receiving fitting. Meaning, push it in and then pull back just a bit so that when you tighten the ferrule down it does not push the glass into the fitting too much and stress fracture the glass. I use glass tubing connections (1/4") all the time and I rarely break the tubing with this technique.

The jet switch is due to flow differences between the two columns and the blow on the FID is to mix the gases by the glow plug. I have not done the latter but there are number of posts about this process.

Best regards.