GC COLUMN-METHOD QUESTION PLEASE

[mebecker1]

I have another Validation question revolves around this material 2-Ethoxyethyl Methacrylate (EOEMA). The method is Purity By GC.
INJECTION is NEAT...

1. Column used is 10% OV-225 6 ft x 1/8 in x 2.1 mm
2. Only column available for second methodology is 10% OV-101 6 ft x 1/8 in x 2.1mm

I do not think this is going to work using that second column. I have been doing a lot of work on this and the EOEMA is polar and the OV-225 is polar. and the method is a gradient temp beginning at 80 C with a initial time 2.00 min and rate of 10 C/min with final T = 200C.

I do not think I can use this 10% OV-101. It is a non-polar column and the only mechanism for separation of this EOEMA is by boiling point. I do not think this will give me a clear picture of all the impurities in the sample and I need those to do % Purity determination.

Think I am going to have to request a column that is polar..Something like a Carbowax with PEG...Maybe even a standard polar packed column. I think anything else is going to require the method be changed. Have to avoid that at all cost. I see a lot of options..could even use the DB-WAX capillary column I just ordered but would have to change the method ESPECIALLY flow rate. Cannot use 30 cc/min Helium with a capillary column.

This is a s SPECIAL CASE for validation and I have to compare 2 methodologies. All operating parameters are kept constant have to implement a different column with different retention characteristics but keep all other parameters in the method constant.

Please definitely let me know your thoughts. I have spoken with Agilent and Supelco...So I really do not think this OV-101 will fly....

[chromatographer1]

The non-polar column will separate the saturated propionate from the acrylate and it does a better job on branched chains and different length esters than the polar column.

The issue is of course, peak shape and the polar column will give a better peak shape, but with the exception of the saturated/unsaturated separation, it will perform less well than the non-polar column.

I would suggest a 1301/624 phase or a 1701 phase or a 20% Phenyl methyl silicone, especially the 1301/624 phase. A 5% phenyl is also an option.

I assume you are using glass columns and white Chromosorb support.

You can use a capillary column at 30cc/min but you need a 5m 0.25mm ID back restrictor FSOT tubing attached to a 15 to 30m 0.53mm ID analytical column. This would be more inert but you might be required to use a Restek injection liner where you attach the column directly to the analytical column (direct injection, no split). I would use an injection of less than 100 nanoliters if possible.

This might be too difficult to implement for an ordinary lab situation.

best wishes,

Rod

[mebecker1]

The non-polar column will separate the saturated propionate from the acrylate and it does a better job on branched chains and different length esters than the polar column.

The issue is of course, peak shape and the polar column will give a better peak shape, but with the exception of the saturated/unsaturated separation, it will perform less well than the non-polar column.

I would suggest a 1301/624 phase or a 1701 phase or a 20% Phenyl methyl silicone, especially the 1301/624 phase. A 5% phenyl is also an option.

I assume you are using glass columns and white Chromosorb support.

You can use a capillary column at 30cc/min but you need a 5m 0.25mm ID back restrictor FSOT tubing attached to a 15 to 30m 0.53mm ID analytical column. This would be more inert but you might be required to use a Restek injection liner where you attach the column directly to the analytical column (direct injection, no split). I would use an injection of less than 100 nanoliters if possible.

This might be too difficult to implement for an ordinary lab situation.

best wishes,

Rod

The columns we have are SS not glass. 20% OV-101 on Chromosorb WHP packing, mesh size 100/120, pre-conditioned. I am going to run a sample myself today. I do not think I will see those impurities and I have to see them. I need good peak shape to do a %Purity for the EOEMA. IMHO, best way to go would be to change out all columns to capillary but that would require a full re-write of the method. That will not fly either as the objective of the project is to validate the method as is. I could used the DB-WAX capillary I just ordered for a different % Purity validation..and would have great chromatography. But, then would have to choose another capillary column and that is not going to go over well.

I will look into the columns you suggested. Thanks .

UPDATE: I am going to try and run the EOEMA on the OV-101 and see what I get. Really, is the only way I can tell if it is a viable column. Have to use a packed column for the validation so as to preserve the method as is. No one has tries this column yet. I just think would be far easier to get a polar packed colum...mid-polar...WE SHALL SEE WHAT HAPPENS!!! TYVM

[chromatographer1]

Be aware that a 20% loading of phase on a W support is an overload and this may affect peak shape and the efficiency of the column.

Lowering of oven temperature for additional separation and to increase the k' of the peaks involved is a better idea than increasing the phase loading over 12%.

best wishes,

Rod