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It is very common to use sodium vapour lamp in BA/ PK study to
avoid photodegradation. Is there any technical rationale/
information available for this (preferably published original
I have recently come across one laboratory which used array of
zero voltage light bulb, which I felt is an irrational thing to
do, by common sense. Anyone knows about frequency of the light
emitted by these bulbs.
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Dear Dr Prashant,
in my opinion, there is simply no rationale (or at least just a 'rumour').
I guess, there was a 'knowledge' transfer from (instable) stock
solutions to plasma
samples, which does not hold any verification.
The best way to avoid sodium vapor lamps, is to validate the
degradation: to get
preliminary information analyse a set of spiked plasma samples
exposed for e.g. one
hour (or whatever your sample preparation time is) to differing
fluorescent lights, halogen bulbs, direct sunlight, daylight through
a window... I
expect in many cases you will end up with no differences (besides analytical
variability) at all.
If you find some degradation, validate the method for conditions with the least
annoyances (e.g. 'without exposure to direct sunlight').
If you have a method already validated with a Na-lamp, cross-validate
it for more
human conditions: run a set of 'illuminated' QC samples (LLOQ, low,
high) in triplicates for three days with the 'dark' method for a
formal proof of
In my expirience 'dark room conditions' are just bad for analytical
precision: it is
very difficult to handle (mostly yellow) plasma samples in
monchromatic yellow light.
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