MolSieve packed column rapid analysis

Hi all,

For our analysis we are using the following MolSieve packed column:
#G3591-80074 MolSieve 5A, 80/100, 3 ft (0.91 M), 1/8 in. OD, 2 mm ID.

We need to replace this column to get twice faster analysis. For example for CH4 which has the time of retention of 4.5min at the moment, we need such column to get it on 2.3min.
In this situation, the only solution is to replace the #G3591-8007 column with one similar by the length, but with different parameters (mesh value, or to use 13X type instead of 5A, which has faster time of analysis).

Please note that changing the method parameters is not accepted, the only solution is packed column replacement with a faster analysis one.

We are thinking to replace with the following column:
#G3591-80028 MolSieve 13X, 45/60, 3 ft (0.91 M), 1/8 in. OD, 2 mm ID.
But we are not sure on it, so please advice.

Thank you in advance.

Best regards,

  • Hello

    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:

    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,

  • 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.



  • 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,

  • 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.



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