Quantitative on-line vs. off-line NIR analysis of fluidized bed drying with consideration of the spectral background.
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®--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.
Research Center Pharmaceutical Engineering, Graz, Austria.
Nicolas
N
Heigl
Daniel M
DM
Koller
Benjamin J
BJ
Glasser
Fernando J
FJ
Muzzio
Johannes G
JG
Khinast
D000388:Air; D002021:Buffers; D002130:Calcium Phosphates / Q000737:chemistry*; D002138:Calibration; D002626:Chemistry, Pharmaceutical / Q000379:methods; D005079:Excipients / Q000737:chemistry; D016018:Least-Squares Analysis; D015999:Multivariate Analysis; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012016:Reference Values; D015203:Reproducibility of Results; D012984:Software; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013678:Technology, Pharmaceutical / Q000295:instrumentation* / Q000379:methods; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D002021:Buffers; D002130:Calcium Phosphates; D005079:Excipients; D014867:Water; D019904:Polymethyl Methacrylate; C020243:calcium phosphate
Dibasic calcium phosphate anhydrous; Fluidized bed; Near-infrared spectroscopy; Off-line; On-line; Partial least squares regression; Spectral background