L1 Column

[jayroseville58]

As per USP procedure, can anyone suggest any column brand that I can use with the following specifications? Thanks.

3.0-mm x 25-cm; 3µm packing L1

[Gerhard Kratz]

L1 stands for any C18 material, no matter if irregular or spherical particles, from 3µm to 13µm particle size. I would recommend to select one of the newer phases from one of the respected manufacturers.
By the way that is the challenge when you want to follow an USP method. First you need to look for 3mmID columns, 25cm should be not the problem. At the end you will find minimum 5 manufacturers who will offer 3µm material C18 in the requested dimensions. I mean Manufacturers. But still you will be not sure which column brand was used in the USP method. Maybe you can ask the manufacturers to look up your application if it was published before going to USP. Good luck.

[jayroseville58]

L1 stands for any C18 material, no matter if irregular or spherical particles, from 3µm to 13µm particle size. I would recommend to select one of the newer phases from one of the respected manufacturers.
By the way that is the challenge when you want to follow an USP method. First you need to look for 3mmID columns, 25cm should be not the problem. At the end you will find minimum 5 manufacturers who will offer 3µm material C18 in the requested dimensions. I mean Manufacturers. But still you will be not sure which column brand was used in the USP method. Maybe you can ask the manufacturers to look up your application if it was published before going to USP. Good luck.

Now I'm clarified about the idea of L1 column, another question is, can I use 15cm x 5µm as alternative to 25cm x 3µm (multiplying the values gave me 75cm.µm)? Are they just equivalent? Thanks.

[tom jupille]

No! Check the USP for their regulations regarding adjustments (which are allowed) versus modifications (which require revalidation). You are allowed to decrease the particle size to 50%, but *not* increase. Column length can be adjusted +/- 50% (I thing -- I'm doing this from memory). Diameter can be adjusted +/- 50% but the flow must be adjusted to maintain the same linear velocity (i.e., adjust flow in proportion to the square of the diameter).

In any case, you must meet system suitability. In the case you propose (shorter column with larger particles), this may be a problem because you will lose plate count as a result.

[jayroseville58]

No! Check the USP for their regulations regarding adjustments (which are allowed) versus modifications (which require revalidation). You are allowed to decrease the particle size to 50%, but *not* increase. Column length can be adjusted +/- 50% (I thing -- I'm doing this from memory). Diameter can be adjusted +/- 50% but the flow must be adjusted to maintain the same linear velocity (i.e., adjust flow in proportion to the square of the diameter).

In any case, you must meet system suitability. In the case you propose (shorter column with larger particles), this may be a problem because you will lose plate count as a result.

"Thanks Tom, your help is highly appreciated"