I am working with a recombinant peptide with a low molecular weight of 5 kDa. I want to use a sepharose FF column to purify this peptide. But the columns I found are used for peptides with large molecular weights.
If you don't limit yourself to Sepharose FF resins, there are other options that can be used to purify small peptides like yours. For example, Sephadex G-50 (fine) has a separation range of 3000-20,000 for globular proteins. Consult the Cytiva web site for information about gel filtration resins.
https://www.cytivalifesciences.com/en/us/shop/chromatography/resins/size-exclusion?sort=NameAsc&chunk=1
Which "contaminants" do you need to get of? As Adam recommended, Sephadex G-50 is a good option to try (look for NAP-10 or PD-10 desalting columns in your lab). Depending on the properties of your protein and it's current purity, other methods like ion exchange might be worth consideration.
As you know the sequence of your peptide, also consider having it synthesized ;)
I strongly recommend using Superdex 30 Increase 10/300 GL
It has a fractionation ability between 1-7 kDa... You should take into account that it has a bit of hydrophobic interaction affinity. Therefore AA sequence of the target peptide is also critical. You may modify the mobile phase by adding a small amount of organic during application...
Good luck