MolSieve packed column rapid analysis

Hello alprovornii

To be more secure about what column is the best, I would advise you to download and use our GC Method translator. You can access for free at the link below:

https://www.agilent.com/en/support/gas-chromatography/gccalculators

Using this tool you can add your current method and simulate how the method would be with a new column in terms of how fast or how more efficient it would became based on the dimensions. You can't change the method a lot but at the software you can simulate any changes, as temperature ramp, carrier gas and etc if needed.

If you change column chemistry, it's harder to predicted because elution order or time retention can change in a not proportional way in relation to the current column

Thank you,

Hi Mariana,

Thank you for your reply and recommendations.

I've checked the GC Method translator, and it is a really useful tool, but for capillary columns only. As I am using the packed columns, there is no way to define this column in Method Translator, so to simulate the optimum parameters.

The only solution is to find someone you have experience using different type of MolSieve packed columns with different parameters and could help me to replace my column with a suitable one to have twice faster analysis.

Best regards,
Alexandr 

Hi Mariana,

Thank you for your reply and recommendations.

I've checked the GC Method translator, and it is a really useful tool, but for capillary columns only. As I am using the packed columns, there is no way to define this column in Method Translator, so to simulate the optimum parameters.

The only solution is to find someone you have experience using different type of MolSieve packed columns with different parameters and could help me to replace my column with a suitable one to have twice faster analysis.

Best regards,
Alexandr 

Hi alprovornii,

please post a chromatogram of you analysis with the method parameters for us to see what separation you need to have. Please also indicate what parameters can be changed and which cannot.

Regards,

Norbert

Hi Nobert,
Thank you for reply.

At the moment we use the following column: #G3591-80074 MolSieve 5A, 80/100, 3 ft (0.91 M), 1/8 in. OD, 2 mm ID.
Method parameters: column flow - 20ml/min (Ar carrier gas), oven temp - 40 C for 5min, after that with 10 C/min to 175 C.

CH4 has the time of retention of 4.5min at the moment, we need such column to get it on 2.3min.
Please see the picture of chromatogram we've got at the moment:


We nee to have the elution of CH4 twice faster, because between CH4 and C2H2 we also have CO2 when we activate the nickel catalyst. But because the interval between CH4 and C2H2 is too short we can't get CO2.
If we change any method parameters it don't solve the problem too much, so the only solution is to replace the MolSieve column with a faster one (13X instead of 5A, or other mesh size), to get twice faster elution time of CH4 (approx 2.3min) for the same parameters of method.

Thank you in advance.

Best regards,
Alexandr

Hi Alexandr,

it is a very tricky one. You will loose 50% plates when using half of the length M5A, but also M13X has a lower efficiency (especially in the front part). You can test it by doubling your column flow/head pressure and see what's happening. We can make any length of packed column custom made, so if you need 1.5 ft. x 2 mm x 1/8 in. it can be done. Please visit the Custom Column Shop for more details.

Regards,

Norbert

Dear Norbert,
Thank you for your reply and clarification.

Could you precise how much faster are eluting the components on 13X packing column is comparison with 5A, considering that both columns have same parameters (length, mesh, ID etc)?

Thank you in advance.

Best regards,
Alexandr

Dear Alexandr,

unfortunately this is impossible to do as the selectivities of the phases (M 5A vs.M 8A pore sizes) is different, you will have less separation power for all small molecules. There is no more air separation on M13X. That leaves only the trial-and-error approach. I still would go with the higher flow option if possible.

Regards,

Norbert

Hi Norbert,
Ok, thank you for your explanation.

Best regards,
Alexandr