We prepared two kinds of fine particles by treating lactose monohydrate (Lac) with the same formulation in a fluidized-bed granulator, which differed in the spraying air pressure. Raman intensities of treated Lac during processing were measured using a handheld-type Raman spectrometer and plotted against particle size. As particle size increased, Raman intensity decreased in both operating conditions. A linear relationship between them was observed, and regression lines were obtained with good correlation coefficients as calibration curves in both operating conditions. We also prepared two other types of fine particles by treating Lac with the same formulation in a fluidized-bed granulator, which differed in the scale or processing mechanism. The particle size could be successfully predicted using the calibration curve obtained taking powder porosity into consideration. Based on this study, we present a new at-line approach in process analytical technology to monitor and predict particle size using a handheld-type Raman spectrometer.
Keywords: at-line approach; monitoring; particle size; powder porosity; process analytical technology; raman spectroscopy.