Abstract

There are currently no techniques that allow <i>facile</i> on-line determination between amorphous and crystalline material. Herein, a new colorimetric method, perichromism, has been developed to distinguish between amorphous and crystalline material, based on diffuse reflection ultraviolet-visible (UV-visible) spectroscopy. A probe molecule, phenol red, at 0.1% w/w concentration was added to sucrose and dissolved in water. The solution was freeze-dried, which resulted in an amorphous excipient with the probe molecule incorporated in an intimate mixture. The samples were then stored at a selected controlled temperature and relative humidity to allow control of crystallization of the sucrose. The amorphous or crystalline nature of each sample, both with and without the addition of the phenol red probe molecule, was monitored through X-ray diffraction, differential scanning calorimetry, and Raman spectroscopy. It was found that sucrose remained amorphous when stored in an atmosphere with a relative humidity below 32%; above this level, crystallization occurred. It was found that the presence of the probe molecule did not alter the extent of crystallinity of sucrose. Analysis of the samples containing the phenol red probe by diffuse reflection spectroscopy revealed that spectra could be classified into two groups depending on the λ_max. Furthermore, correlation of the diffuse reflection spectra with X-ray diffraction and differential scanning calorimetry data showed that sucrose was amorphous in one group and crystalline in the other group, thereby revealing that diffuse reflection spectroscopy can, when phenol red is used as a probe molecule, quickly and easily determine whether sucrose is crystalline or amorphous.

Identification and investigation of the vibrational properties of crystalline and co-amorphous drugs with Raman and terahertz spectroscopy

Wei Liu, Yu Liu, Jiaoqi Huang, Zhongquan Lin, Xuancheng Pan, Xiaojun Zeng, Marc Lamy de la Chapelle, Yang Zhang, and Weiling Fu
Biomed. Opt. Express 10(8) 4290-4304 (2019)

Low temperature growth of high crystallinity GeSn on amorphous layers for advanced optoelectronics

Haofeng Li, Jeremy Brouillet, Alan Salas, Xiaoxin Wang, and Jifeng Liu
Opt. Mater. Express 3(9) 1385-1396 (2013)

Spectroscopic properties of thulium-doped crystalline materials including a novel host, La₂Be₂O₅: a comparative study

Vikas Sudesh and E. M. Goldys
J. Opt. Soc. Am. B 17(6) 1068-1076 (2000)

Light-assisted drying for anhydrous preservation of biological samples: optical characterization of the trehalose preservation matrix

Madison A. Young, Daniel P. Furr, Riley Q. McKeough, Gloria D. Elliott, and Susan R. Trammell
Biomed. Opt. Express 11(2) 801-816 (2020)

Measurement of the relative optical phase between amorphous and crystalline regions of the phase-change media of optical recording

Rongguang Liang, J. Kevin Erwin, and Masud Mansuripur
Appl. Opt. 39(13) 2167-2173 (2000)