title: Raman spectroscopic measurement of tablet-to-tablet coating variability.
abstract: We report new results suggesting the feasibility of Raman spectrometry as a tool by which to examine the variability of tablet coatings. Our experiments feature a probe that can operate with a revolving laser focus to average content and coating non-uniformity. Raman spectral changes are correlated with tablet exposure times in a pan coater by means of partial least squares (PLS) multivariate analysis. Statistical models are found to be improved by pre-processing schemes that emphasize spectral changes while minimizing the effects of background light scattering and fluorescence. These pre-processing techniques include multiplicative scatter correction (MSC) and standard normal variate (SNV) transformation, used in concert with Savitzky-Golay second derivative smoothing (SGSD). The two approaches give comparable results yielding R2 values for PLS calibration and cross-calibrated prediction variance regression of 0.999 and 0.997, respectively. Correlation results and model residual values demonstrate that Raman spectroscopy serves sensitively to reflect the coating thickness of the tablets studied.
authors.affiliation: Department of Chemistry, Purdue University, 425 Central Drive, West Lafayette, IN 47907, USA.
authors.forename: Saly
authors.initials: S
authors.lastname: Romero-Torres
authors.forename: José D
authors.initials: JD
authors.lastname: Pérez-Ramos
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Morris
authors.forename: Edward R
authors.initials: ER
authors.lastname: Grant
mesh_terms: D000465:Algorithms; D015999:Multivariate Analysis; D013059:Spectrum Analysis, Raman / Q000379:methods* / Q000592:standards; D013608:Tablets, Enteric-Coated / Q000032:analysis*; D013678:Technology, Pharmaceutical / Q000295:instrumentation / Q000379:methods; D013997:Time Factors
chemical_list: D013608:Tablets, Enteric-Coated