Dear GroupBack to the Top
I want to know that
1) howcan we extract the acididc drug bye liquid-liquid extraction,
but the drug is soluble only in ethyl acetate.
But if we do the plasma study by LC so much interfences are coming so
how can we avoid it
Please suggest me
Dear Prashant,Back to the Top
Recollect the first principles of liquid-liquid extraction:
Liquid-liquid extraction is basically a process of selective extraction
of an analyte from a liquid matrix using an immiscible solvent. Here
selectivity can be achieved by choosing a suitable solvent (polarity)
into which analyte of interest is selectively extracted (solubility).
Classically this is done by using an immiscible solvent (usually non polar) to
extract analyte of interest from your matrix (usually aqueous). Therefore, when
you want to extract your analyte into a relatively non-polar solvent (such
as ethyl acetate, dichloromethane, diethyl ether etc) you need to have your
drug to be in un-ionised state for it to easily partition into organic
So, since your analyte of interest is an acid, you need to acidify your
matrix (plasma in your case) in-order to keep acidic analyte in
un-ionised state (if analyte is a base, it is vice-versa) before the extraction
step. Then try and extract with different non-polar solvents which can give a
more selective extraction with no interference peaks at retention time of
your analyte or internal standard.
Parameters you can manipulate to achieve selectivity and avoid
interference peaks are:
1. Polarity of extraction solvent - you can use mixture of solvents to
finely adjust the polarity for eg. ethyl acetate:dichloromethane in
1:1, 2:1 or 1:2 etc.
2. Time of extraction - If you use a selective solvent you can reduce
extraction time by which you can avoid extracting interfering components
3. Reconstitution solvent composition
If extraction recovery of analyte is close to 100% but have interference
peaks, then you can try and avoid detecting interference peaks at the
detector level by selecting a suitable wavelength on UV detector
(doesn't have to be lambda max of your analyte) provided you are ready to
sacrifice sensitivity for selectivity.
Hope this helps.
Hello,Back to the Top
In addition to message of Kasiram Katneni,
besides trying a selective extraction using mixtures
of organic solvents or improving selectivity using a
more selective lambda (for UV or fluorescence) ,
another possibility to resolve your drug (if you have
extracted from matrix but you still have a lot of
endogenous compounds) is to use a 3.5 um column, which
usually is 2 times more efficient in comparison with a
5 um column, for the same analysis time. You cal also
try to resolve your peak by changing the stationary
phase, the pH, buffer.....
Dept. of Pharmaceutical Technology and Biopharmaceutics
Faculty of Pharmacy
University of Medicine and Pharmacy "Iuliu Hatieganu"
13, Emil Isac
Cluj-Napoca, Cluj 3400, Romania
Hi Prashant,Back to the Top
What Vlase said was perfectly true. One can always try and change
mobile and stationery phases to avoid interferences and achieve specificity.
And in each case (mobile and stationery phases) you have plethora of
parameters to manipulate. Among all pH of mobile phase is one useful parameter that can be easily manipulated and works well in changing retention properties of analyte or interfering components. This way you can try and resolute
your analyte of interest from interfering components if at all they exhibit
differential pH dependent solubilities.
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