IR Cell – Nujol mull
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Transcript IR Cell – Nujol mull
IR sample preparation
for solid samples
What is a mull?
a mull a suspension of solid sample in mineral
oil
It is used to make a thin-film cell from a solid
sample
Thin film IR cells
Salt (NaCl) discs are used
To hold the sample
So the holder won’t absorb infrared light
and only sample absorption is detected
Sample preparation
so dry the sample well
because water etches the IR discs
and emulsifies with oil letting less light through
How do I make a mull?
grind
the sample
to a smooth
powder
add mineral oil
and mix it
well
What should the mull be like?
the mull
should look
and spread
like soft butter
use clean gloves
to work with salt discs
put on an extra pair
of gloves
to protect cells
from anything
aqueous on your
regular gloves
applying the mull
use a rubber policeman
to spread
a thin layer
on one disc
lower the 2nd disc
on top of the 1st
and twist the discs
to spread sample evenly
placing discs in cell holder
use your finger
to make a platform
in the cell holder
lower in
the NaCl discs
do not wedge them
gently
place lid
on top
slide into position
in light beam
close
sample
compartment
remove gloves
before using
keyboard
to clean discs
add a few drops
of chloroform
to each disc
rub gently
to clean off
all traces of sample
…
Keep discs dry
replace
in desiccator
after cleaning
…