Water determination in body butter and creams - Mettler Toledo

Water determination
4
Problems with
sticky samples are a
thing of the past.
METTLER TOLEDO CosmeticsNews 3
Water determination in body butter and creams –
Visco-Spoon improves accuracy
Albert Aichert,
Senior applications chemist
at METTLER TOLEDO
■ Albert, could you please explain the exact
nature of the problem to our readers?
Due to moisture in the air, Karl Fischer titration
has to take place in a hermetically
sealed titration vessel. Liquid samples are
normally added by means of a syringe,
solid samples by a weighing boat. It is
essential to keep the opening time of the
system to an absolute minimum in order
exclude errors due to ambient moisture.
■ What exactly is the problem with sticky
or viscous samples such as cosmetic
creams?
We cannot add them with a syringe as
they don’t flow and we cannot add them
Viscous samples, such as cosmetic creams, are a challenge for water
determination by Karl Fischer titration. Entering the sample into the
hermetically sealed titration vessel requires scraping and fiddling with
a spatula and often results in increased ambient moisture. We asked
Albert Aichert, senior applications chemist at METTLER TOLEDO, to de-
scribe a new accessory that greatly facilitates water determination in
the cosmetics lab.
like a solid as they are too sticky. In the
past this has often led to problems and
erroneous results.
■ You say ‘in the past’. What has changed
now?
We have developed Visco-SpoonTM, which
is essentially a spatula attached to a
ground sleeve stopper. When we want to
measure a sample, we simply load some
of the cream onto the spatula and weigh
it. Visco-Spoon is then transferred to
the titration beaker where it replaces the
standard stopper. The spatula, and more
importantly the sample, is thereby immersed
into the titration solvent which
gradually dissolves the cosmetic cream
METTLER TOLEDO DL38 KF titrator
and allows simple and quick water content
determination.
■ This sounds easy and straight forward.
What is your experience with this method?
Are there any potential challenges? Can
you give us some expert tips?
Since cosmetic creams contain a high
proportion of fats and oils, it is advisable
to use a suitable co-solvent such as 1-decanol
to facilitate sample dissolution. A stir
time of up to five minutes before titration
further helps dissolution and care should
be taken to keep sample size as small as
possible. We have analyzed a number of
cosmetics samples and are very pleased
indeed with the results (see insert). Visco-
Sample weight No. samples result RSD
Hand cream 15 - 20 mg 6 68.2 % 0.6 %
Body butter mango 35 – 45 mg 5 43.7 % 0.8 %

Albert Aichert is senior applications
chemist and a well
known authority on Karl Fischer
titration. He has analyzed
many hundreds of different
samples and written various
publications on the practical
aspects of this analytical
technique. He is responsible
for training METTLER TOLEDO
sales and support staff and
has traveled extensively in
order to share his knowledge
in customer seminars and conferences.
In his limited spare
times he likes to climb the
peaks of the Swiss Alps.
Spoon TM is a very simple accessory but
has a great effect on the everyday life of
chemists. Incidentally, it was developed
in collaboration with a customer from
a large consumer goods company and is
therefore truly from the practitioner for
the practitioner.
■ Albert, many thanks for your information.
www.mt.com/Karl-Fischer
www.mt.com/Titration
When loading the sample, Visco-Spoon TM
works like any other spatula. Weighing
it empty and full allows determining the
sample weight by difference.
The DL38 has been designed for users with
applications ranging from routine Karl-
Fischer titration to more demanding needs,
such as external extraction, high-speed
homogenizing and Bromine index.
Visco-Spoon TM fits into the ground sleeve
joint of the titration beaker. That way the
sample is immersed in the solvent mixture
and moisture ingress is minimized during
sample loading and titration.
METTLER TOLEDO CosmeticsNews 3
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