Italian to English Medical Medical: Pharmaceuticals manufacturing

In particular, I'm not sure what 'colonna' is referring to in this particular context. It's part of a document about risk and impact assessments in the pharmaceutical industry and this is given as one situation, under the heading 'methods and specifications', in which a risk or impact assessment need not be done within the manufacturing site:

Modifiche alla concentrazione e volume di iniezione della soluzione mantenendo inalterato ***il carico del campione in colonna***

Other items listed under the same heading are as diverse as - changes to the documents which don't change the contents, safety information for the staff, and changes to the final volume which does not include a change in the concentration

Any help or ideas gratefully received