Solid-state properties of Nifurtimox. Preparation, analytical characterization, and stability of an amorphous phase.

Nifurtimox (NFX) is a nitrofuran derivative used to treat Chagas disease, a neglected disease caused by the protozoan Trypanosoma cruzi. The drug is very sparingly soluble in aqueous media and no other solid phases of NFX have been reported to date. The preparation of the amorphous mode of NFX is reported, as well as its characterization by hot stage microscopy, thermal (differential scanning calorimetry and thermogravimetric analysis), spectroscopic (solid state nuclear magnetic resonance, mid-infrared, and near-infrared), diffractometric and functional (powder dissolution rate) means. The stability of the new phase was investigated. This was characterized using thermal, spectroscopic, and diffractometric methods, finding out its spontaneous reversion to the crystalline state, as sign of instability. In addition, the amorphous material proved to be sensitive to temperature, pressure, and mechanical stress, all of which accelerated phase conversion. However, it was able to remain stable in a model polymeric amorphous solid dispersion with PEG 4000 for more than one month. An approach for monitoring the conversion of the amorphous phase to its crystalline counterpart under thermal stress by chemometric analysis of mid-infrared spectra at different temperatures is also disclosed.

Application of Laser-Induced Breakdown Spectroscopy in Detection of Cadmium Content in Rice Stems.

The presence of cadmium in rice stems is a limiting factor that restricts its function as biomass. In order to prevent potential risks of heavy metals in rice straws, this study introduced a fast detection method of cadmium in rice stems based on laser induced breakdown spectroscopy (LIBS) and chemometrics. The wavelet transform (WT), area normalization and median absolute deviation (MAD) were used to preprocess raw spectra to improve spectral stability. Principal component analysis (PCA) was used for cluster analysis. The classification models were established to distinguish cadmium stress degree of stems, of which extreme learning machine (ELM) had the best effect, with 91.11% of calibration accuracy and 93.33% of prediction accuracy. In addition, multivariate models were established for quantitative detection of cadmium. It can be found that ELM model had the best prediction effects with prediction correlation coefficient of 0.995. The results show that LIBS provides an effective method for detection of cadmium in rice stems. The combination of LIBS technology and chemometrics can quickly detect the presence of cadmium in rice stems, and accurately realize qualitative and quantitative analysis of cadmium, which could be of great significance to promote the development of new energy industry.

Qualitative and quantitative analyses of Compound Danshen extract based on 1H NMR method and its application for quality control.

In this study, a new approach using 1H NMR spectroscopy combined with chemometrics method was developed for qualitative and quantitative analyses of extracts of Compound Danshen Dripping Pills (CDDP). For the qualitative analysis, some metabolites presented in Compound Danshen extract (CDE, extraction intermediate of CDDP) were detected, including phenolic acids, saponins, saccharides, organic acids and amino acids, by the proposed 1H NMR method, and metabolites profiles were further analyzed by selected chemometrics algorithms to define the threshold values for product quality evaluation. Moreover, three main phenolic acids (danshensu, salvianolic acid B, and procatechuic aldehyde) in CDE were determined simultaneously, and method validation in terms of linearity, precision, repeatability, accuracy, and stability of the dissolved target compounds in solution was performed. The average recoveries varied between 84.20% and 110.75% while the RSDs were below 6.34% for the three phenolic acids. This 1H NMR method offers an integral view of the extract composition, allows the qualitative and quantitative analysis of CDDP, and has the potential to be a supplementary tool to UPLC/HPLC for quality assessment of Chinese herbal medicines.