X-Ray Scattering
through the α/β transition, there were significant changes of ∼1% in the individual unit cell parameters—and therefore in crystal dimensions—on passing through the transition in either direction. Tis had the effect of causing crystals to jump off a solid surface, such as a microscope slide, on passing through the transition. Han Wu recently reran the analysis of P and its phase
transitions, which in her prior work from 2010 took 10 hours (with 200L liquid nitrogen dewar). Using the Ganesha 300XL and the Linkam stage (Figure 5) with the 1L liquid nitrogen dewar, she was able to complete the entire range of phase transformations from 80°C to -170°C in a couple of hours and collect each data set in just 2 seconds using WAXS (Figure 6). She was also able to actually see the crystals “jumping” using the open DSC system and microscope (Figure 7) and correlate these images with the DSC curve (Figure 8). Te temperature-controlled SAXS/WAXS system at CNIE
has shown it is capable of excellent sample characterization performance, with several key advantages: 1) time: quickest
scan in 1 second, which is powerful for phase identification and polymorph screening; 2) high signal-to-noise ratio: minimal scattering from air and windows due to whole-vacuum setup; 3) small-angle scattering from 0.004° to 5° in 2θ and wide-angle scattering up to 60° in 2θ; 4) temperature-dependent studies: accurate temperature control from as low as -190°C up to 300°C using just 1L of liquid nitrogen to achieve controllable heating/ cooling; 5) characterization of short-lived intermediate phases.
Conclusions SAXS/WAXS has great potential for rapid polymorph traditional XRD is not
screening when adequate and
synchrotron access is not readily available. Te CNIE system is much more than an SAXS, and in many application areas, it is superior to most lab XRD instruments in terms of time and energy saving, with comparable results. Te incorporation of the Linkam stage enables collection of temperature-dependent measurements, making it possible to detect new polymorphs and phase changes in both solid and liquid samples.
Figure 6: XRD pattern (WAX scattering data) from Ganesha 300XL and the Linkam HFSX350-CAP temperature-control capillary stage for pyroglutamic acid, characterizing two phase changes at around (a) 70–80°C, fast transition and (c) -150°C, slow transition, going from α to β and α to α’, respectively. Figures 6b and 6d show the respective reverse transitions. Data collected at temperature intervals of 10°C using WAXS in 2 seconds.
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