Enhancement of infrared spectral images for maximizing chemical information by minimizing baseline interferences.

The popularity of spectral images in many areas of analysis has greatly increased during the last decade due to the development of charge-coupled device (CCD) and infrared sensitive cameras. Large amounts of spatial information can be obtained in short periods of time. The general goal in analytical chemistry is to convert spectral images into chemical images, which show the spatial locations of various chemical components. Self-modeling multivariate curve resolution methods can be used to extract pure component spectra from the mixture spectra in images and produce chemical images. However, there is a difficulty in processing infrared spectral images due to large pixel-to-pixel baseline variations. Herein, a method for minimizing baseline interferences using fast Fourier transform (FFT) filtering in both the spectral and spatial domains is discussed. The methodology is demonstrated on a microscopic sample of butter contaminated with non-pathogenic E. coli and on a cross-sectional sample of rabbit aorta containing plaque. The processing to reduce baseline effects improved the spatial resolution without compromising the spectral resolution.

Comparison of near infrared and microwave resonance sensors for at-line moisture determination in powders and tablets.

In this paper we demonstrate the feasibility of replacing KF for water content testing in bulk powders and tablets with at-line near infrared (NIR) or microwave resonance (MR) methods. Accurate NIR and MR prediction models were developed with a minimalistic approach to calibration. The NIR method can accurately predict water content in bulk powders in the range of 0.5-5% w/w. Results from this method were compared to a MR method. We demonstrated excellent agreement of both NIR and MR methods for powders vs. the reference KF method. These methods are applicable to in-process control or quality control environments. One of the aims of this study was to determine if a calibration developed for a particular product could be used to predict the water content of another product (with related composition) but containing a different active pharmaceutical ingredient (API). We demonstrated that, contrary to the NIR method, a general MR method can be used to predict water content in two different types of blends. Finally, we demonstrated that a MR method can be developed for at-line moisture determination in tablets.

Solid-state interactions of a drug substance and excipients and their impact on tablet dissolution: a thermal-mechanical facilitated process-induced transformation or PIT.

The polymorphic and/or pseudo-polymorphic phase transformation of Drug Z API, from Form I to Form II, occurs during the wet granulation step. It was observed that dissolution of the tablets slowed down under certain manufacturing conditions. Factors responsible for the slowdown in tablet dissolution were investigated in this study. Two levels of shear during premixing and two wet granulation drying temperatures were investigated by measuring the dissolution profiles of the tablets. The interaction between API and excipients was examined using differential scanning calorimetry and X-ray powder diffraction. When stearic acid was present with Form I as the starting material in the formulations, the dissolution slowdown was significant under the conditions of higher shear during premixing or higher drying temperature. However, there was little impact of lower shear premixing or lower drying temperature. When Form I was replaced with Form II, the slowdown in dissolution was mainly observed with higher drying temperature. The tablet dissolution slowdown was due to the interaction between Form II and stearic acid that facilitated the formation of Form I. The transformation back to the Form I material reported here may be classified as a thermal-mechanical facilitated PIT and represents a new subclass of the phenomena.

[Biogas yield and its relations with the duration and temperature of mixed anaerobic fermentation of livestock dungs and wheat straw].

To approach the relationships between the biogas yield ot mixed anaerobic termentation of livestock dungs and crop straw and the fermentation duration and temperature is the key of selecting fermentation materials for rural household biogas, determining optimal fermentation temperature, and improving the reuse efficiency of agricultural residues. In this paper, a batch of experiments under the condition of 8% mass fraction of total solid were conducted in a self-manufactured anaerobic fermentation reactor, with pig dung, cattle dung, and wheat straw as fermentation materials, and the substrate of constant temperature fermentation pool as inoculation substance. The biogas yield, fermentation duration, and optimal temperature were determined. It was shown that the cumulative biogas yield of mixed anaerobic fermentation of pig dung and wheat straw was 2.4 times higher than that of the fermentation of pig dung alone, but no significant difference was observed between the cumulative biogas yields of the mixed fermentation of cattle dung and wheat straw and the fermentation of cattle dung alone. The optimal fermentation temperature for the mixed anaerobic fermentation was above 30 degrees C, and the fermentation duration was about 60 days. The fermentation duration was not always shortened by increasing temperature, and it would be not feasible to only use temnerature to determine the duration of anaerobic fermentation.