The application of powder X-ray diffraction (PXRD) for the detection and quantification of low levels of a solid-state chemical impurity, BrettPhos oxide, in an active pharmaceutical ingredient is discussed. It is demonstrated that with appropriate methodology and experimentation, the impurity levels of as low as 0.07% w/w could be detected reliably and limit of quantification of 0.10% w/w could be achieved by PXRD, using a laboratory X-ray source. Method development, validation, and benchmarking using conventional high-performance liquid chromatography are presented in the manuscript highlighting the robustness and reproducibility of such measurements.

Li4Ti5O12 (LTO) and its doped analogues Li4Ti4.95M0.05O12 (M = Al3+, Co3+, Ni2+, and Mg2+) were synthesized and characterized using in situ PXRD to monitor the phase transitions during the sol–gel synthesis of the spinel material. These results are complimented by thermogravimetric analysis, which illustrates the decomposition of the materials synthesized, where the final LTO products are seen to form at approximately 550 °C. The material has an amorphous structure from room temperature, coupled with a crystalline phase which is speculated to be H2Ti2O5·H2O. This crystalline phase disappears at 250 °C, with the material still in the amorphous state. The crystalline LTO phase starts at approximately 550 °C, with anatase co-crystallizing with the spinel phase. Rutile appears at 600 °C and co-crystallizes with the final product at 850 °C, where anatase is no longer seen. The rutile impurity remains present after cooling the material to room temperature, and results indicate that prolonged heating at 850 °C is required to reduce the rutile content. Rietveld refinement of diffraction patterns show that the unit-cell parameter increases with increasing temperature, coupled with a decrease when cooling the sample. The crystallite sizes follow the same trend, with a significant increase above temperatures of 750 °C.

Ag3O was synthesized by jet-milling magnetron-sputtered Ag–Ag2O thin films. Heating the jet-milled powders in air and N2 from 40 to 148 °C at ambient pressure produced Ag3O-rich powders. The phase composition and unit-cell parameters of the jet-milled powders were measured as a function of temperature with in situ X-ray powder diffraction experiments from −186 to 293 °C. Ag3O was also produced by ball milling and sonicating jet-milled films at ambient conditions. The phase composition, unit-cell parameters, and thermal-reaction rates indicate nonstoichiometric Ag3O was produced from the reaction of metastable, nonstoichiometric Ag2O (cuprite structure) and ccp Ag. The thermal expansion of Ag3O is anisotropic; below 25 °C, the a-axis expansion is about twice the c-axis expansion resulting in a negative slope of c/a(T). The reversal of the sign of c/a(T) near 25 °C is dramatic. The thermal reaction is arrested when the temperature is rapidly increased from ambient to 130 °C. Ag3O is metastable and decreases its unit-cell volume during kinetic decomposition to Ag when heated above ambient temperature in air and nitrogen. The relative volume expansion of Ag3O is about 80% less than Ag at room temperature and below. The suite of nonstoichiometric Ag3O produced by heating displays a linear relation between c/a and unit-cell volume at room temperature. The c/a and unit-cell volume of a hydrothermally grown Ag3O single crystal reported in a published structure determination was the Ag-rich, low-volume end member of the linear series. The c/a and unit-cell volume are sensitive indicators of the oxygen content and state of disorder.

Validating phase quantification procedures of powder X-ray diffraction (XRD) data for an implementation in an ISO/IEC 17025 accredited environment has been challenging due to a general lack of suitable certified reference materials. The preparation of highly pure and crystalline reference materials and mixtures thereof may exceed the costs for a profitable and justifiable implementation. This study presents a method for the validation of XRD phase quantifications based on semi-synthetic datasets that reduces the effort for a full method validation drastically. Datasets of nearly pure reference substances are stripped of impurity signals and rescaled to 100% crystallinity, thus eliminating the need for the preparation of ultra-pure and -crystalline materials. The processed datasets are then combined numerically while preserving all sample- and instrument-characteristic features of the peak profile, thereby creating multi-phase diffraction patterns of precisely known composition. The number of compositions and repetitions is only limited by computational power and storage capacity. These datasets can be used as input files for the phase quantification procedure, in which statistical validation parameters such as precision, accuracy, linearity, and limits of detection and quantification can be determined from a statistically sound number of datasets and compositions.

In this work, SnS1−xSex ternary nanobelts were synthesized by a facile hydrothermal method without the assistance of surfactants. The structure, morphology, microstructure, compositions, chemical valences, phonon modes, and optical band gaps of the SnS1−xSex nanobelts were characterized in detail. The results indicate that the SnS1−xSex nanobelts have uniform one-dimensional morphology and are single crystals with high crystallinity. Se is incorporated into the SnS lattice to substitute for S-forming ternary SnS1−xSex alloy. With the increase of Se doping concentration, the optical band gaps of the nanobelts gradually decrease from 1.15 to 1.01 eV, confirming the tunable optical property achieved here.

X-ray powder diffraction data for estra-4,9-diene-3,17-dione, C18H22O2, are reported [a = 9.236(7) Å, b = 10.294(4) Å, c = 15.471(1) Å, unit cell volume V = 1471.11 Å3, Z = 4, and space group P212121]. All measured lines were indexed and are consistent with the P212121 space group. No detectable impurities were observed. The single-crystallographic data of the compound are also reported [a = 9.2392(7) Å, b = 10.2793(5) Å, c = 15.4822(7) Å, unit cell volume V = 1470.37(15) Å3, Z = 4, and space group P212121]. Both single-crystal and powder diffraction methods can get the similar structure data.

The crystal structure of hyoscyamine sulfate monohydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Hyoscyamine sulfate monohydrate crystallizes in space group P21 (#4) with a = 6.60196(2), b = 12.95496(3), c = 20.93090(8) Å, β = 94.8839(2)°, V = 1783.680(5) Å3, and Z = 2. Despite the traditional description as a dihydrate, hyoscyamine sulfate crystallizes as a monohydrate. The two independent hyoscyamine cations have different conformations, which have similar energies. One of the cations is close to the minimum-energy conformation. Each of the protonated nitrogen atoms in the cations acts as a donor to the sulfate anion. The hydroxyl group of one cation acts as a donor to the sulfate anion, while the hydroxyl group of the other cation acts as a donor to the water molecule. The water molecule acts as a donor to two different sulfate anions. The cations and anions are linked by complex chains of hydrogen bonds along the a-axis. The powder pattern has been submitted for inclusion in the Powder Diffraction File™ (PDF®).

The crystal structure of cephalexin monohydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Cephalexin monohydrate crystallizes in space group C2 (#5) with a = 27.32290(17), b = 11.92850(4), c = 16.75355(8) Å, β = 108.8661(4)°, V = 5166.99(3) Å3, and Z = 12. Although the general arrangement of molecules is similar to that in cephalexin dihydrate, the structural differences result in very different powder patterns. The crystal structure is characterized by alternating layers of hydrogen bonds and van der Waals contacts parallel to the bc-plane. The water molecules occur in clusters. Five of the six protons in the water molecules act as donors in O–H⋯O hydrogen bonds. The sixth hydrogen atom acts as a donor to two different phenyl ring carbon atoms to form bifurcated O–H⋯C hydrogen bonds. Each cephalexin molecule is a zwitterion, containing ammonium and carboxylate groups. The ammonium ions form N–H⋯O hydrogen bonds to carboxylate groups and water molecules, as well as to carbonyl groups. The powder pattern is included in the Powder Diffraction File™ as entry 00-065-1417.