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Help a biochemist!

JDirks jdirks at direct.ca
Tue Aug 31 18:31:07 EST 1999


Help!  I need some info regarding properties of quaternary ammonium chloride
compounds.  I am specifically dealing with benzalkonium chloride
(BAK)(alkylbenzyl dimethyl ammonium chloride).
I have some questions regarding extraction of BAK from aqueous to organic
phases.  BAK is soluble in water and polar solvents, so I presume it will be
soluble in chloroform.
In the problem that I'm working on, a blood sample suspected to contain BAK
was extracted (1:5) with chloroform/isopropanol.  The organic phase was
retained, the chloroform was evaporated, the residue was treated with BSTFA
in TCMS and pyridine, and GC-MS was performed.  BAK was not detected.
Questions:
Am I crazy? Since BAK is completely water soluble, chloroform/isopropanol
would not extract it.  True?
Much of the literature I have read regarding purification of BAK or other
quaternary ammonium chlorides from biological matrixes states that they can
be extracted by ion-pair extraction techniques.  The literature states that
the best ions for the protocol are Cl<Br<I.  I am unfamiliar with this
technique, but I can envision a mechanism where the aliphatic portion of the
molecule forms a micelle with the inorganic ion in the middle.  True?
Since Cl was the counter-ion used in the purification, and taking the water
solubility into account, the purification protocol used was not adequate and
it is not surprising that the GC-MS was negative.  True?

Thanks in advance for your help!
Julie Dirks
jdirks at direct.ca or geoffnjulie at wwdb.org






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