Studies on the influence of uniformity of particle size of powder, tapping and sample replacement for diffusion...

The extent of deviation factors and the influence of pre-processing of spectra for a quantitative application of reflectance NIR measurement against powder sample were examined. Lactose monohydrate (NGLM), a medical additive was used for this study. Ground lactose monohydrate (GLM) and NGLM were measured by NIR reflectance spectroscopy. In the wave number range from 12000 cm(-1) to 4000 cm(-1), the ratios of absorbance values (a.v.) between the wave numbers of GLM and NGLM were almost the same and no influence of intensity of absorbance through the measurement range was observed concerning heterogeneity of particle size. Absorbance values of NGLM were decreased with increasing number of tapping without a bit difference of the change of a.v. The several statistical parameters of a.v. from both samples were estimated. The relative standard deviation (RSD) and 95% confidence intervals (CIs) of a.v. on successive measurements at a fixed position in GLM and NGLM vials were almost the same. However, the RSD and 95% confidence of absorbance value of NGLM were larger than these GLM, i.e., RSD: 0.66% for NGLM, 0.42% for GLM. The 95% of CI of NGLM was ten times larger than that of GLM in five replacement positions. The two kinds of baseline corrections, the SNV and MSC processing were examined to evaluate the extent of influence against a.v. The 95% CI calculated from a.v. by the SNV pre-processing showed a wider range compared with that from no pre-processing and MSC pre-processing. These results suggest that the statistical confidence of a.v. would also change by pre-processing. It is important to consider the statistical confidence of a.v. for precise quantitative application of the reflectance NIR spectroscopy.