US EPA

2678382 

Journal Article 

Quantitative on-line vs. off-line NIR analysis of fluidized bed drying with consideration of the spectral background 

Heigl, N; Koller, DM; Glasser, BJ; Muzzio, FJ; Khinast, JG 

2013 

1 

European Journal of Pharmaceutics and Biopharmaceutics
ISSN: 0939-6411
EISSN: 1873-3441 

85 

3 

1064-1074 

24056058 

10.1016/j.ejpb.2013.09.012 

WOS:000330200800027 

Quantitative dehydration studies of dibasic calcium phosphate anhydrous (DCPA) in a small-scale cold-model fluidized bed dryer with process air control were conducted. Near-infrared spectroscopy (NIRS) with partial least squares regression (PLSR) was used to predict DCPAs' residual moisture content. Loss-on-drying (LOD) was employed as a reference method and confirmed the actual moisture content of DCPA. First, dynamic PLSR modeling was carried out, i.e., the NIR spectra were on-line recorded and predicted throughout the drying process. Secondly, PLSR off-line modeling was performed, i.e., samples were consecutively thief-probed from the processor, put into glass vials and analyzed off-line. Furthermore, two background spectra were collected prior to the in- and off-line measurements in an attempt to increase the method's sensitivity, i.e., (i) dry DCPA that was fluidized at respective process air velocity (on-line) or inside a glass vial (off-line) and (ii) Spectralon (R) - a highly reflecting standard reference material made of fluoropolymer. Benefits and drawbacks of the in- and off-line approaches with different spectral backgrounds are discussed in detail. The results indicated that (i) the thief-probed sample amount from the processor and thus the sample weight and (ii) the downtime between thief-probing a sample and its actual analysis via NIRS and LOD can bias the moisture content predictions. (C) 2013 Elsevier B.V. All rights reserved. 

Near-infrared spectroscopy; Fluidized bed; Dibasic calcium phosphate anhydrous; Partial least squares regression; On-line; Off-line; Spectral background