Development of Measurement Tools for High-Throughput Experiments of Synchrotron Radiation XRD and XAFS on Powder Libraries.

We propose to minimize the sampling time for high-throughput measurements of powder X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) in synchrotron radiation. The conventional synchrotron radiation powder X-ray diffraction method requires filling of a capillary tube, but a structure-refining diffraction pattern could be obtained by transferring the crushed powder to a tape and rotating the cassette-tape tool by ±5° around the sample position. XAFS spectra could also be measured with the sample attached to the tape. The time required for sample preparation was greatly reduced, which made high-throughput experiments with powders in synchrotron radiation experiments more accessible.

Applications of Powder X-Ray Diffraction in Small Molecule Pharmaceuticals: Achievements and Aspirations.

Since the discovery of X-ray diffraction and its potential to elucidate crystal symmetry, powder X-ray diffraction has found diverse applications in the field of pharmaceutical sciences. This review summarizes significant achievements of the technique during various stages of dosage form development. Improved understanding of the principle involved and development of automated hardware and reliable software have led to increased instrumental sensitivity and improved data analysis. These advances continue to expand the applications of powder X-ray diffraction to emerging research fields such as amorphous systems, mechanistic understanding of phase transformations, and "Quality by Design" in formulation development.

Quantitation of polymorphic impurity in entecavir polymorphic mixtures using powder X-ray diffractometry and Raman spectroscopy.

Entecavir was used for the treatment of chronic hepatitis B through inhibiting hepatitis B virus. The anhydrous form of entecavir (ENT-A) often appeared as impurity polymorph in the manufacturing process of entecavir monohydrate (ENT-H) such as granulation, drying and compression. Since different crystal forms might affect drug bioavailability and therapeutic effect, it was vital to control the ENT-A content of the drug product. The work aimed to develop useful methods to assess ENT-A weight percentage in ENT-H. Powder X-ray diffractometry (PXRD) and Raman spectrometric methods were applied. Binary mixtures with different ratios of pure ENT-H and pure ENT-A were scanned using PXRD and Raman to obtain spectra. Then peak heights and peak areas versus weight percentage were used to construct calibration curves. The best linear regression analysis data for PXRD and Raman method were found to be R2 = 0.9923 and R2 = 0.9953, in the weight ratio range of 2.1-20.2% w/w% of ENT-A in binary mixtures. Limit of detection (LOD) of ENT-A was 0.38% and limit of quantitation (LOQ) was 1.15% for PXRD method. LOD and LOQ for Raman method were 0.48% and 1.16%. The results showed that PXRD and Raman methods: both were precise and accurate, and could be used for measurement of ENT-A content in the selected weight percentage range. Partial least squares (PLS) algorithm with four data pre-processing methods: including multiplicative scatter correlation (MSC), standard normal variate (SNV), first and second derivatives were applied and evaluated using prediction errors. The best performance of PLS was R2 = 0.9958 with RMSEC (0.44%) and RMSEP (0.65%). Multivariate analysis for Raman spectra showed similar good results with univariate analysis, and would be an advantageous method when there were overlapped peaks in the spectra. In summary, the proposed PXRD and Raman method could be developed for the quality control of ENT-H. And Raman was a more promising method in industrial practice due to its slightly better precision, accuracy and time-saving advantage.

Comparison of the analytical methods (solid state NMR, FT-IR, PXRD) in the analysis of the solid drug forms with low concentration of an active ingredient - 17-ß-estradiol case.

The application of various techniques (FT-IR, PXRD, ssNMR) in the analysis of solid dosage forms with low concentration of an API (17-ß-estradiol hemihydrate, EBHH) was tested. PXRD analysis of Estrofem Mite tablets (EMT) confirmed the presence of the main crystalline excipient, α-lactose monohydrate. In the PXRD pattern of EMT the strong background from polycrystalline excipients, i.e. hydroxypropylmethylcellulose and corn starch was observed. FT-IR spectra were characterized by the broad peaks in the 3000-3600cm-1 region of the OH stretching modes coming from multiple hydrogen bonds that are present in the structures of the excipients (α-lactose monohydrate, corn starch) and API. The only technique which unambiguously confirmed the presence of an API in the EMT was solid state NMR. Despite the tabletting process each of the EMT component retained its characteristic features like relaxation time and T1ρI. Due to the possibility of the manipulation in the experimental registration parameters like recycle delay (RD), evolution time (τ) and contact time (CT) it was possible to perform multiple experiments on the same sample of EMT. The most valuable were the inversion recovery CP experiments in which, by setting the proper values of τ, it was possible to selectively observe the signals of the chosen component of the drug formulation. In this study the great potential of solid state NMR in the analysis of solid dosage forms, as the unique technique that combines the possibility of selective observation of the chosen signals with the non destructive character that enables further analysis of the same sample, was confirmed.

A facile and selective approach for enrichment of l-cysteine in human plasma sample based on zinc organic polymer: Optimization by response surface methodology.

In this research, a facile and selective method was described to extract l-cysteine (l-Cys), an essential α-amino acid for anti-ageing playing an important role in human health, from human blood plasma sample. The importance of this research was the mild and time-consuming synthesis of zinc organic polymer (Zn-MOP) as an adsorbent and evaluation of its ability for efficient enrichment of l-Cys by ultrasound-assisted dispersive micro solid-phase extraction (UA-DMSPE) method. The structure of Zn-MOP was investigated by FT-IR, XRD and SEM. Analysis of variance (ANOVA) was applied for the experimental data to reach the best optimum conditions. The quantification of l-Cys was carried out by high performance liquid chromatography with UV detection set at λ=230nm. The calibration graph showed reasonable linear responses towards l-Cys concentrations in the range of 4.0-1000µg/L (r2=0.999) with low limit of detection (0.76µg/L, S/N=3) and RSD≤2.18 (n=3). The results revealed the applicability and high performance of this novel strategy in detecting trace l-Cys by Zn-MOP in complicated matrices.

In situ monitoring of vapour-induced assembly of pharmaceutical cocrystals using a benchtop powder X-ray diffractometer.

We describe a simple setup for in situ continuous monitoring of vapour-induced transformations of organic solids using a benchtop powder X-ray diffractometer. Proof-of-principle application of this setup to model pharmaceutical cocrystals reveals complex reactivity, transformations of reaction intermediates within minutes, and a simple route to the rarely observed monoclinic form of the pharmaceutical cocrystal of carbamazepine and saccharin.

Limits of visual detection for finasteride polymorphs in prepared binary mixtures: analysis by X-ray powder diffraction.

Finasteride (FNT) is a drug that inhibits human enzyme type II 5α-reductase that metabolizes testosterone into dihydrotestosterone. There are two enantiotropic polymorphs with known crystal structure: designated as forms I and II. Identification and control of these polymorphic forms in mixtures can be performed using X-ray powder diffraction (XRPD) data and Rietveld method (RM). As experimental conditions may limit the detection of minority phases in mixtures, it is interesting to show what are these limits for some usual and one high-resolution equipment. So, in this work, we discuss the parameters to find the limit of the detection in binary mixtures of forms I and II of FNT according to each experimental condition. The samples analyzed were binary mixtures prepared with anhydrous polymorphs of the drug FNT. These samples were measured in four diffractometers with different experimental condition. These equipments represent the main resolutions generally used for drug analysis by XRPD. For the development of this work, a batch of form I was obtained pure, and another batch with forms I and II was used to obtain pure form II by heat treatment. Depending on the experimental condition, the polymorphs could be detected in a proportion as low as 0.5 wt%. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3567-3575, 2014.

Combined synchrotron X-ray tomography and X-ray powder diffraction using a fluorescing metal foil.

This study realizes the concept of simultaneous micro-X-ray computed tomography and X-ray powder diffraction using a synchrotron beamline. A thin zinc metal foil was placed in the primary, monochromatic synchrotron beam to generate a divergent wave to propagate through the samples of interest onto a CCD detector for tomographic imaging, thus removing the need for large beam illumination and high spatial resolution detection. Both low density materials (kapton tubing and a piece of plant) and higher density materials (Egyptian faience) were investigated, and elemental contrast was explored for the example of Cu and Ni meshes. The viability of parallel powder diffraction using the direct beam transmitted through the foil was demonstrated. The outcomes of this study enable further development of the technique towards in situ tomography∕diffraction studies combining micrometer and crystallographic length scales, and towards elemental contrast imaging and reconstruction methods using well defined fluorescence outputs from combinations of known fluorescence targets (elements).

The MYTHEN detector for X-ray powder diffraction experiments at the Swiss Light Source.

The MYTHEN single-photon-counting silicon microstrip detector has been developed at the Swiss Light Source for time-resolved powder diffraction experiments. An upgraded version of the detector has been installed at the SLS powder diffraction station allowing the acquisition of diffraction patterns over 120 degrees in 2theta in fractions of seconds. Thanks to the outstanding performance of the detector and to the calibration procedures developed, the quality of the data obtained is now comparable with that of traditional high-resolution point detectors in terms of FWHM resolution and peak profile shape, with the additional advantage of fast and simultaneous acquisition of the full diffraction pattern. MYTHEN is therefore optimal for time-resolved or dose-critical measurements. The characteristics of the MYTHEN detector together with the calibration procedures implemented for the optimization of the data are described in detail. The refinements of two known standard powders are discussed together with a remarkable application of MYTHEN to organic compounds in relation to the problem of radiation damage.

A methodology for measuring in situ lattice strain of bulk polycrystalline material under cyclic load.

The material response of polycrystalline materials under cyclic loading is not fully understood. Even during uniaxial loading, individual grains embedded within the polycrystalline material can experience complicated strain histories. By quantifying the deformation state at the crystal level, we can begin to understand the conditions that lead to fatigue failure. An in situ powder diffraction method was developed and employed at the Cornell High Energy Synchrotron Source to measure the aggregate crystal response at various points in a material's life using synchrotron x ray. A set of experiments was conducted using a load frame capable of exerting cyclic uniaxial loads on a specimen. A high speed x-ray shutter was developed to synchronize the x-ray beam and the loading cycle. Using the high speed shutter, the evolution of the lattice strains for the families of crystallographic planes was measured while the aggregate was under cyclic uniaxial loading, thus monitoring a live evolution of lattice strain in a cyclically loaded specimen. The methodology is demonstrated using uniaxial cyclic specimens machined from oxygen free conductivity (OFHC) copper sheet.

Application of a hybrid pixel detector to powder diffraction.

Results obtained using a hybrid pixel photon-counting detector in powder diffraction experiments are presented. The detector works at room temperature and its dynamic response ranges from 0.01 photons pixel(-1) s(-1) up to 10(6) photons pixel(-1) s(-1). The pixel sizes are 0.33 mm x 0.33 mm for a total area of 68 mm x 68 mm. On recording high-resolution diffraction patterns of powders, a reduction of the experimental time by more than a factor of 20 is obtained without loss of data quality. The example of an X-zeolite shows that such detectors can be used for very demanding anomalous experiments. In situ experiments of quenching liquid oxides show that frames of 0.01 s can be achieved for studying such processes.

High-resolution powder diffraction study of purple membrane with a large Guinier-type camera.

X-ray diffraction patterns from a film of oriented purple membranes, which comprise two-dimensional crystals of bacteriorhodopsin (BR) trimers, were recorded with a 1 m-pathlength Guinier-type camera at SPring-8 BL40B2. A well focused X-ray beam and a camera with a high angular resolution of 0.024 degrees enabled a powder diffraction profile with very sharp and well separated peaks to be obtained up to a resolution of 2.3 A. Using integrated diffraction intensities up to a Bragg spacing of 4.2 A, a cluster of bulky amino acid residues and the head group of the BR chromophore are apparent in the electron density map projected along the membrane normal. Thus, a combination of synchrotron X-rays and large Guinier camera can be used for analyzing the conformational changes of BR in the intact state. In addition, the method might be extended to the structural analysis of film materials composed of two-dimensional arrays of nanoparticles.

X-ray powder diffraction beamline at D10B of LNLS: application to the Ba2FeReO6 double perovskite.

A new beamline, fully dedicated to X-ray powder diffraction (XPD) measurements, has been installed after the exit port B of the bending magnet D10 at the Brazilian Synchrotron Light Laboratory (LNLS) and commissioned. The technical characteristics of the beamline are described and some performance indicators are listed, such as the incoming photon flux and the angular/energy resolutions obtainable under typical experimental conditions. The results of a Rietveld refinement for a standard sample of Y2O3 using high-resolution data are shown. The refined parameters match those found in the literature, within experimental error. High-resolution XPD measurements on Ba2FeReO6 demonstrate a slight departure from the ideal cubic double-perovskite structure at low temperatures, not detected by previous powder diffraction experiments. The onset of the structural transition coincides with the ferrimagnetic ordering temperature, Tc approximately equal to 315 K. Subtle structural features, such as those reported here for Ba2FeReO6, as well as the determination and/or refinement of complex crystal structures in polycrystalline samples are ideal candidate problems to be investigated on this beamline.

Combinatorial screening employing nylon loops and micro-X-ray powder diffraction.

A combinatorial screening method is described that employs nylon loops and micro-X-ray powder diffraction. The nylon loops are used to position the sample in a three-circle X-ray diffractometer in such a way as to allow for Gandolfi-like scans. These scans maximize mechanical tumbling of the sample, which in turn results in higher quality data. The diffractometer utilizes a pinhole source and two-dimensional area detection for rapid data collection. The method can be readily automated by employing single-crystal screening procedures. The combinatorial analysis of the three known polymorphs of D-mannitol is discussed and a simple procedure to produce all three polymorphs from the same starting solutions is presented.

Single molecule diffraction.

For solving the atomic structure of organic molecules such as small proteins which are difficult to crystallize, the use of a jet of doped liquid helium droplets traversing a continuous high energy electron beam is proposed as a means of obtaining electron diffraction patterns (serial crystallography). Organic molecules (such as small proteins) within the droplet (and within a vitreous ice jacket) may be aligned by use of a polarized laser beam. Iterative methods for solving the phase problem are indicated. Comparisons with a related plan for pulsed x-ray diffraction from single proteins in a molecular beam are provided.

High-resolution and high-intensity powder diffractometer at BL15XU in SPring-8.

A new ultra-high-resolution powder diffractometer for synchrotron radiation has been constructed at beamline BL15XU, SPring-8. The two-axis diffractometer is optimized for high-flux and high-coherent X-ray beams, which are provided by combining a planar undulator and a large offset rotated-inclined Si(111) double-crystal monochromator. The optics design of the diffractometer is based on transmission geometry, which employs a capillary specimen and reflection geometries using a flat-plate specimen. The intensity data are collected using a 2theta step-scan technique in both geometries. The diffractometer can be arranged in a variety of optical configurations, e.g. simple receiving slits, flat crystal analyzer of Ge(111) or Si(111), and in-vacuum-type long horizontal parallel slits. A minimum full width at half-maximum against 2theta was 0.00572 degrees at lambda = 0.63582 A for the (200) reflections from Si powder in the transmission geometry employing the Ge(111) crystal analyzer. A wide temperature range (32-900 K), which is controlled by a He/N(2) gas stream system, is available. 288 structure parameters of a zeolite ZSM-5 sample have been demonstrated to successfully refine with a R(wp) value of 6.96% by a Rietveld analysis of the high-resolution powder diffraction data from a 1 mm-diameter capillary specimen.