RI noise

Record: 753

Category: Column Problem
Product: GPC
Sample:

Question
seeing large noise when using KD-806M while KF-806M is fine.

Answer
As we talked, I have asked our application specialist regarding the DMF noise problem.
There are two things she thought that could be the cause.

1. When you replace eluents (THF – 0.2M LiBr/DMF) do you introduce DMF with LiBr straight after/before THF?
She mentioned that solubility of LiBr in THF is low thus Br- might remain in the system. This residual may react with oxidation products in THF and overtime, cause yellowish product. RI may be detecting this product. In order to prevent this, you should use DMF without salt to clean the system between the solvent replacement.

2. Some older type RI detector requires “Optical Balance” setting depends on the solvent used.
When setting is not done properly, you may see large noise with the RI detector that requires this setting,
If you are using an older type RI detector, please check if “Optical Balance” is centered.
Higher the salt concentration, it will create higher reflective index differences, so that may appear as large noise.

 
 
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