Freund-Vector Leads Way in PAT Processing and Pellet Manufacturing

Detection of Moisture Using a NIR Filter Photometer on Dynamically Moving Particles in a Rotor Processor


On November 4-5, 2019, Mitch Crawford, Associate Process Scientist, Freund-Vector presented a poster at the American Association of Pharmaceutical Scientists (AAPS) show in San Antonio, TX on “Detection of Moisture Using a NIR Filter Photometer on Dynamically Moving Particles in a Rotor Processor”.

The purpose of this paper was after following the FDA’s PAT (Process-Analytical-Technology) initiative in the early 2000s, numerous studies have been conducted utilizing full spectrum near infrared (NIR) sensing technology to monitor moisture in granulation and drying processes. In order to achieve good “mapping” of the process, the sample being presented to the sensor needed to be “at rest” and in contact with the sensor/optics in order to achieve usable spectra. This study investigated the feasibility of using a NIR filter photometer on a dynamically moving product bed not in contact with the sensor.

The poster focused on correlating NIR absorbances to moistures on materials being processed in a VFC-Lab 3 GXR-35 conical rotor with an Innovative Technologies RS 1000 On-line moisture gauge.  Each trial was a spherical granulation, with varying material compositions.  From the start of the trial, moisture is increased significantly (material dependent) throughout the granulation process then the material is dried back to or below starting moisture.  NIR absorbance is being recorded every second during the entire trial and several samples are taken to measure moisture using an LOD machine.  The data showed a strong correlation between NIR absorbance and moisture levels. From this conclusion, a model can be created that allows you to predict the moisture level of the product during the process using an NIR photometer probe without disrupting the process.

Spherical granulation requires very low airflows compared to top spray granulation. Final particle size is determined by spray rate, atomization pressure, and temperature; sphericity is determined by rotor speed. Granules processed in the GRANUREX® (GXR) rotor exhibit several favorable characteristics including superior flowability and compressibility from its spherical shape. Fine control of the conical rotor process results in very narrow particle size distributions. Minimal excipients are used, so each granule contains up to 97% active content. Granule-to-granule content uniformity is superior to other granulation methods.

The ability of the GRANUREX® (GXR) to control and distribute very low process airflow volumes allows for greater processability of micronized powders, which are essential for creating small, uniform multiparticulate dosage forms. The conical shape of the rotor orders the flow of the product past the spray gun, allows for larger batch sizes than conventional flat rotors, and creates superior mixing than what is possible with the flat rotors. Ball mounted spray and powder guns which are in the product bed provide efficient spray transfer onto the product with minimal spray drying effects. These improvements have made conical rotor technology a superior option for the creation of multi-particulate dosage forms.

As a result, Moisture content of dynamically moving materials in a spherical granulation process can be successfully monitored using a single wavelength filter photometer.


To read the full details of this paper, please click here.

To learn more about Freund-Vector’s GRANUREX® technologies, please visit or send an email to

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