On-line concentration measurement for anti-solvent crystallization of β-artemether using UV–vis fiber spectroscopy

Concentration monitoring is essential for quality control of crystallizations. This work establishes the technical feasibility of Ultraviolet (UV) fiber spectroscopy for on-line concentration measurement of anti-solvent crystallization of β-artemether, where ethanol was selected as solvent and water was used as anti-solvent. The orthogonal signal correction (OSC) algorithm was selected to preprocess the UV spectra, and the results showed that the wavelength shift of UV maximum absorbance of β-artemether in ethanol+water solvent mixtures can be effectively eliminated by OSC algorithm. Then models for prediction of β-artemether concentration based on Lambert–Beer law were developed, and the models were verified by comparison between the training set and the validation set, as well as its directly application to the anti-solvent crystallization process of β-artemether. The results show that the model is suitable for on-line concentration measurement of anti-solvent crystallization of β-artemether, with reasonable accuracy and precision.     

2 μm spectroscopic investigation of Tm3+-doped tellurite glass fiber

TmF₃ doped TeO₂–ZnO–La₂O₃ (TZL) glasses and fibers have been prepared by the conventional melt-quenching and suction casting methods, respectively. 2 μm emission properties and energy transfer mechanisms of the TZL glasses and fibers have been analyzed and discussed. The oscillator strength, Judd–Ofelt parameters, radiative transition probability and radiative lifetime of Tm³⁺ have been calculated based on the absorption spectra and Judd–Ofelt theory. The maximum emission cross-section of Tm³⁺ is 6.9 × 10^?21 cm² near 2 μm. Emission spectra have been obtained from both TZL fibers and bulk glass when excited with a 794 nm pump. The results of 2 μm emission spectra indicate that the line width of Tm³⁺ measured in fibers is narrower than that in the bulk glass sample. The peak position of the emission spectra shifts to longer wavelength with increment of the fiber length.