Powder blending

1
Powder blending
The photograph shows the empty blender with the
Zeiss Corona Spectrometer used for the NIR
measurements of powder mixing.
2
Instrumentation
Zeiss Corona 45 NIR Spectrometer Non- invasive
reflectance spectrometer 128 element InGaAs array
detector 15 mm sample spot Operated in absorbance
mode Spectra acquired every 0.5 s average of 10
scans with 31 ms integration Reflective white
paper inside vessel
3
NIR Spectrum Aspirin
4
NIR Mixing Profiles 8956 cm-1
The slide shows the change in the signal at 8956
cm-1 when aspirin is mixed into Avicel. As the
amount of aspirin is increased, the time required
to achieve a stable signal increases. A plot of
the average signal for the last 100 s against the
concentration of aspirin is given in the next
slide.
5
NIR Calibration Aspirin in Avicel
The slide shows that in addition to being able to
monitor the state of mixing, the amount of
aspirin in the mixture can be quantified,
although the calibration response curve is not
linear.
6
Monitoring of Multi-Component Systems

• 20 g Citric Acid mixed into 75 g Avicel at 50 rpm
  after 300 s mixer stopped at 900 s
• Mixing continued for 300 s at 50 rpm, then 10 g
  aspirin added and mixed for 900 s
• NIR spectra acquired at 0.5 s intervals 10
  co-added 32 ms scans
• Acoustic spectra acquired at 1 s intervals 2 MHz
  Sample rate, 4.1 k points

NIR measurements were made when citric acid was
added to Avicel, mixed, and then aspirin added.
7
NIR Mixing Profiles at Low Wavenumber Region
6086 cm-1 Aspirin Peak
6841 cm-1 Citric Acid Peak
The slide shows the change in the signal obtained
at an aspirin peak and a citric acid peak when
citric acid and then aspirin are added to Avicel.
The results show the non-selective response of
NIR spectrometry (particularly for measurements
at the aspirin peak in this example).
8
NIR Mixing Profiles at High Wavenumber Region
8669 cm-1 Citric Acid Peak
8956 cm-1 Aspirin Peak
Similar information to the previous slide but at
a higher wavenumber region.