Although sodium azide can be added to a solution to prevent microbial growth it is
not effective at removing growth that has already occurred.
In a system that is contaminated with microbial growth it is more effective to flush with
50:50 acetonitrile/water to remove the growth from the system. Note that the column
should be flushed with water to remove any buffer salts (e.g. phosphate) before washing
with high organic.
It may also be necessary to clean or replace guard columns and in-line filters as these
are likely to be blocked.