Near-infrared spectroscopy for the in-line characterization of powder voiding part I: Development of the methodology

In-line near-infrared spectroscopy (NIR) spectra were acquired and analyzed to assess the relationship between physical and chemical properties of voiding powders and their spectral changes. NIR spectra were obtained for powders voiding from a conical glass funnel while the powder flow was recorded with a digital camera. Two different approaches using in-line NIR spectra were developed to measure the flow interruptions in the powder voiding process. The first approach uses the noise in the spectra and the second is based on the baseline changes. The new method was also used to evaluate the effects of humidity on the flow of microcrystalline cellulose samples and to evaluate the effect of mixing method on the flow properties of the blends obtained. The method described may be applied to other applications that involve powder flow, and the same spectra may be used to determine drug concentration.