ed into the housing, a universal rotary valve,
shorter tubing, which leads to less sample consumption
and some innovations on the spectrometer
itself.
What does it mean exactly?
The previous MPA device still had a laser tube
that usually had to be replaced after two to three
years. The new MPA II now has a laser diode with
a life expectancy of more than 10 years, which is
why BRUKER grants a 10-year guarantee on the
moving parts of the even more modern interferometer
and on the laser diode. But it should also
be mentioned that older MPA devices are still in
operation after almost 20 years. That speaks for
the longevity of our technology.
The more sensitive detector for reflection
measurements also enables solid and semi-solid
products to be analyzed better. It is also important
for day-to-day operations that the data measured
with the MPA II are compatible with the measurement
data of the older MPA or the TANGO spectrometer.
At the end of the day, it's always about
the best possible spectrum recording and smooth
calibration transfer.
Another important technical feature is the
new, more compact homogenizer pump with
preheater for heating the (raw milk) sample to
approx. 40 ° C. The homogenization at 180-200
bar pressure ensures the finest distribution of the
fat phase and thus a homogenized raw milk sample
for maximum accuracy. Only a few companies
have this very specific know-how of the design of
the homogenization.
It should be noted that the homogenizing
valve is actually only essential for raw milk. For
all other liquid products, the peristaltic pump is
sufficient. This protects the homogenizer in the
long term and thus achieves a considerably longer
service life.
What are the real advantages of the
Bruker MPA II Dairy Analyzer compared
to other analysis systems?
A decisive difference compared to the classic
MIR process lies in the layer thickness used. With
classic MIR spectrometers, a thin layer, usually
35 μm, is necessary, which excludes liquid products
with particles or sugar crystals. Bruker uses
a high-precision Hellma flow cell made of quartz
glass with a layer thickness of 1,000 μm. Highly
viscous samples or samples with particles can
also be easily measured there.
In contrast to the CaF2 cells for analysis in
the mid-infrared, which wear out over time,
the layer thickness of quartz glass always
remains the same, regardless of which medium
is conveyed through the cell and how
often. This enables a consistently high precision
of the measurement and therefore
the spectrometer does not require regular
standardization
with sample series from
external laboratories.
Another great advantage is the significantly
more flexible sample intake: in many
laboratories not only sample beakers are used,
but also, for example, already filled cardboard
boxes or milk bottles. To do this, the arm can
be tilted and easily adjusted in height.
For the measurement of solid and semi-solid
samples on the integration sphere in reflection,
such as cheese or milk powder, there is a
variety of sample vessels to choose from.
What are the key advantages in practice
besides the longer warranty period?
Due to the new design of the tubing, the
sample volume used has been reduced and
several repeat measurements can be carried
out with standards. The cleaning solution
canisters are now integrated into the housing
and the fill level is monitored. Handling
has also been significantly improved in terms
of easier cleaning and maintenance. With
the exception of the valve, there are basically
hardly any components that are subject
to wear and tear, because the motor of the
homogenizing pump installed on the back is
Interview 17
oil-mounted and reliably delivers the required
set pressure. You can even change the valve
or the hoses yourself with a little skill. Otherwise,
the BRUKER service will gladly take
care of it. But in principle the demands on
the operating personnel are low, because the
device works fully automatically under software
control as soon as the sample is added.
Which international regulations are
there for the practical application of NIR
technology?
The first ISO standard 21543 | IDF 201 for the
application of NIR in the milk sector appeared
in 2006. However, it only contained examples
for the analysis of butter, cheese and milk powder
and in practice NIR has long been used for
many more types of samples. A working group
was then set up at the International Dairy
Federation
(IDF), of which I became the leader,
to bring this IDF and ISO standard up to date.
For this purpose, it was first looked at which
applications there are in industrial practice.
Since some things were not known or scientifically
published, the peer-reviewed IDF Bulletin
497 "Applications of Infrared Spectrometry
for the Analysis of Milk and Milk Products"
was created, which documents many practical
examples. It was important to show here that
there can be different approaches and results
that do not necessarily have to be very precise,
but should be sufficiently precise and robust
for practice. This paper was then the basis for
the creation of the new ISO21543 | IDF201,
which was published in 2020, which for the
first time includes the analysis of raw milk with
NIR and also defines measurement principles
such as transmission and transflexion.
This covers practically all milk variants and
milk products that can be analyzed with NIR
in the laboratory. In addition, the ISO 23291
/ IDF 248 “Guideline for the Application of
in-line IR and NIR”, which covers process analysis
in the milk sector, was added in 2020.