Improved Pharma’s continued collaboration with expert colleagues in the field of amorphous studies has resulted in a new publication. The article can be downloaded for free by clicking on this link. This free access expires on February 11, 2022. This article highlights the extreme value of using synchrotron x-ray pair distribution (PDF) analysis to access the sameness of multiple amorphous preparations of the same material.

Early results of this research were shared at the 2019 joint SPS-XRPD-2 and PPXRD-16 meeting in Switzerland. This previous publication concluded that time-resolved, high-energy x-ray pair distribution PDF experiments could be used to track subtle structural changes in organic amorphous materials at different humidity values. Low density water was observed to strongly hydrogen bond to amorphous indomethacin with a structure very different to that of bulk water.

This new article expanded the study by including multiple sources and preparations of amorphous indomethacin. It was found that the fabrication method and storage conditions influenced the amorphous structure. Only the samples which began as the gamma form resulted in x-ray amorphous forms. Melt-quenched alpha and beta phases formed crystals or mixed amorphous and crystalline forms. Furthermore, some samples of the dry amorphous form showed a largely unhindered rotation of the chlorobenzyl ring whereas others showed preferred torsional angles consistent with those observed in the known isomers.

Amorphous indomethacin samples were also studied under conditions of high humidity. It was found that water molecules formed hydrogen bonds with the indomethacin molecules leading to partial hydration of the amorphous form. The strength of these hydrogen bonds was found to be similar to those between indomethacin dimers or chains in the dry amorphous form.

It’s long been known that synchrotron PDF analysis can provide valuable information about the structure of amorphous materials. These studies on different preparations of amorphous materials illustrates how this technique can be used to access the sameness of materials.

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