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The following message was posted to: PharmPK
Dear all,
I had a controversial discussion with my friend and would like to
clarify this:
How many among you have the opinion that Liquid Liquid Extraction is
efficient only when monitoring the analysis at 254nm and above, and
is less efficient at 210nm and below compared to Precipitation and
SPE extraction techniques.
Awaiting your response,
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The following message was posted to: PharmPK
Depends on what you are looking for. 210 will certainly be absorbed by
more molecules than 254 will be. 210 would be a good one to show
contamination. 254 is more selective. Sample would appear cleaner,
but would it be? Most instruments have the capability to run both,
consider that.
Ed O'Connor, PhD
Technical Director, Immunoanalytical
Tandem Laboratories
115 Silvia Street
West Trenton, New Jersey
609-228-0243
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Dear Sankara,
I believe the argument is subjective.
I agree that liquid liquid extraction would bring in more junk that
is like to absorb at 210 nm. But when you have no other option, it
would be better to delay the peak of interest substantially to avoid
any interference. We have done this before and it worked well for us
at least, cheers, Jagannath
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Dear Sankara,
As you said absorbance for the polar interferences at 210 nm would be
more compare to 254 nm. But Liquid-Liquid extraction is more
efficient in getting a cleaner sample then the precipitation method.
This interference is subjective to the solvent employed for
extraction, if the solvent absorbs at lower wavelength interference
will be more even with LLE or precipitation. where as SPE will solve
the problem to a greater extent.
If interference is un avoidable then try to increase the RT of analyte.
Hope this may help you.
Rajareddy
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The lower lambda-max always gives huge interferences than the higher
lambda-max. But while selecting the particular solvent is also a
plays a greater role to avoid the interferences. The solvent should
be a HPLC grade and also need to check the solvent cutoff
wavelength with the particular analyte. Though we evaporating the
organic solvent still some amount would create a problem.
LLE is quite cheaper than SPE, hence most widely used. one more thing
you could do by retain the analyte some more time.
Thanks .I hope this clear your doubts.
A.Karthik
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The following message was posted to: PharmPK
Hi,
LLE is much simpler than SPE, but gives less clean
samples than those using SPE. LLE is more comple than
protein precipitation, but gives cleaner samples. When
we consider if using LLE or protein precipitation,
most of time we consider polarity of the compounds. If
the compound is too polar or not hydrophobic enough,
then LLE does not work. Most of time if using a MS as
a detector and a molecular weight of the analyte is
above 350, protein precipitation works. However, if
using UV as a detector, definitely, it is much less
selective than MS, then it demoands cleaner samples.
In my opinion, we shloud not use wavelength as a
guideline. We have to check our double blank and
single blank to make sure at the wavelength you use
there is no interference peak at the retention time of
the analyte. If there is a interference peak at the
retention of your analyte, then we need to try what we
can to get rid of interference either by column, or by
changing wavelength, or even by changing the detector.
Hope this can help.
Xiaodong
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