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NaOH unchallenged
for cleaning and
sanitizing
odium hydroxide (NaOH) remains
unchallenged as the leading agent to
clean and sanitize chromatography
media and systems and is likely to remain
so. This is the conclusion reached by a
new Application Note that reviews a wide
range of results and experiences.
New Application
Note concludes:
Sanitizing with
NaOH is efficient,
versatile and
inexpensive
The publication initially focuses on
proteins and notes the well-known fact
that NaOH is widely used to remove
proteins from ion exchange, hydrophobic
interaction and gel filtration media. It
then presents data that also shows how
effective the agent is for cleaning a
Protein A affinity column used to purify
monoclonal antibodies.
Even nucleic acids, which can bind
tenaciously to separation media, especially
anion exchangers, can be removed. The
most effective treatment appears to be a
combination of NaOH and NaCl. In
some cases, DNase may also be needed to
completely remove DNA.
Proven inactivation agent
Using NaOH to inactivate viruses,
bacteria, yeasts and endotoxins was also
reviewed. Data presented show that
treatment with NaOH inactivated eight
different strains of virus, including even
highly resistant, non-enveloped species,
such as canine parvovirus and SV-40, as
well as the bovine spongiform
encephalopathy (BSE) agent.
Bacteria and yeast in large amounts can
clog chromatography columns, destroy
the function of separation media and
produce harmful substances such as
endotoxins. However, the Application
Note shows that they too are readily
inactivated by NaOH.
Practical aspects
Practical aspects of sanitizing equipment
and media with NaOH are considered.
Using NaOH is generally straightforward.
Contact times of 30 minutes to 1 hour are
typical and removal from the system is
monitored by simple in-line pH and
conductivity measurements. Afterwards,
NaOH can be disposed without special
measures. NaOH is also inexpensive. And
since it is a bacteriostat, it is
recommended as an effective storage
agent for packed chromatography
columns.
Compatibility with media
Finally, the Application Note discusses the
compatibility of NaOH with different
separation media. The concentration of
NaOH used to clean and/or sanitize
media will often depend on the level of
contamination. The ability of media to
withstand stringent sanitizing conditions
depends on the functional groups,
attachment chemistries, and the stability
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of base matrices to alkaline conditions.
Studies show that the functional stability
of Butyl Sepharose 4 Fast Flow, a
hydrophobic interaction chromatography
medium, is not affected by 4 weeks
exposure to 1.0 M NaOH. More fragile
affinity ligands may not tolerate such
harsh conditions and the concentration of
NaOH will have to be reduced. For
example, Heparin Sepharose 6 Fast Flow
withstands exposure to 0.1 M NaOH for
long periods with no loss of binding
capacity for antithrombin III. When
contamination is severe, 0.5 M NaOH
can be used effectively over shorter
periods. In this case, however,
chromatographic function will decrease
over time.
For more information, request the
Application Note 18-1124-57, ‘‘Use of
sodium hydroxide for cleaning and
sanitizing chromatography media and
systems’’.