Multipoint-NIR-measurements in pharmaceutical powder applications

Anne Heikkilä

Research output: ThesisMaster's thesis

2 Citations (Scopus)


In this paper, multipoint near-infrared (NIR) spectroscopy is used in studying particulate pharmaceutical ingredients and their mixing and granulation processes. Homogeneous mixing of active pharmaceutical ingredients with excipients is essential in getting the correct dosage in the tableting phase. The basic principles of NIR spectroscopy and the associated molecular vibrations are briefly reviewed in the beginning of the work, followed by a summary of typical applications of NIR spectroscopy. A multipoint NIR measurement system developed at VTT is presented in this work. It consists of a spectral camera with fiber-optic inputs, a fiber-optic light source and twelve fiber-optic probes. The performance of the system in the laboratory is thoroughly reported, including signal-to-noise ratio, stability and probe-to-probe variability. The system was also tested in a fluidized bed granulator at Helsinki University. Eight probes were attached in two rows into the granulator, and several granulations were run. The mixing period in the beginning of the granulation process was clearly visible, as well as the changes in the moisture level during liquid spraying and final drying. The study shows that multipoint NIR spectroscopy is a valuable tool in monitoring the granulation process. In particular, it gives information about the macroscopic homogeneity of the fluidized bed.
Original languageEnglish
QualificationMaster Degree
Awarding Institution
  • University of Oulu
Place of PublicationEspoo
Print ISBNs978-951-38-7334-9
Electronic ISBNs978-951-38-7335-6
Publication statusPublished - 2009
MoE publication typeG2 Master's thesis, polytechnic Master's thesis


  • pharmaceutical powder applications
  • fluid bed granulation
  • on-line monitoring
  • moisture content
  • mixing end-point
  • near infrared spectroscopy
  • NIR
  • multichannel spectroscopy
  • fibre-optic probes
  • fibre-optic light sources
  • multipoint-NIR


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