Muramic acid (MA) is a universal chemical marker for
bacterial cell wall polymers (peptidoglycan) present in
complex environmental, industrial, and clinical matrices.
Trace analysis of MA has been limited to a handful of
laboratories because of the lengthy nature of
derivatization
procedures necessary for GC/MS and GC/MS/MS. The
focus of the current report concerns environmental analysis (organic dust) using LC/MS/MS of native MA. Dust
was heated in sulfuric acid to release MA from cell wall
polymers. Acid was removed by extraction with an
organic base. The samples were passed through a hydrophobic C-18 extraction column to remove nonpolar
contaminants. This was followed by binding of MA to a
strong cation-exchange extraction column to eliminate
neutral and anionic components of the sample. MA was
then eluted with hydrochloric acid, which was removed
by evaporation. Analysis was done by microscale LC ES/MS/MS using a custom-made Lichrosphere-diol capillary
column. 13C-Labeled MA was used as an internal
standard. Total sample preparation takes approximately 12
h.
The simplicity of the sample preparation may
eventually
allow MA analysis to be used in a host of applications,
including air monitoring for biocontamination. This is
the
first report, to our knowledge, of microscale LC ES/MS/MS analysis for MA (or, indeed, any other sugar monomer) in a complex matrix.
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