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Topics Covered
Background
Simultaneous DSC/SWAXS
Design and Setup of the S3-MICROcaliX
Measurements and Results
Summary
Background
Scanning calorimetry (DSC) has been combined with small-angle X-ray scattering (SAXS) and was incorporated into the laboratory S3-Micro SWAX-camera system. It is based a on a brilliant, point-focussing laboratory X-ray microsource/optics and equipped with a fast and reliable 1D dual-detector system for simultaneous SAXS and WAXS measurements.
Simultaneous DSC/SWAXS
Simultaneous DSC/SWAXS provides real-time information on the nanostructural events during enthalpic transitions, a topic essential e.g. in food-, drug- and pharma-analytics. In the following application note we present the results of DSC/SWAX measurements of anhydrous milk fat (AMF - 20 mg) performed with the S3-MICROcaliX in a cooling- (80° to -8°C) and subsequent heating- scan from (-8°C to 50°C).
Design and Setup of the S3-MICROcaliX
S3-MICROcaliX in the laboratory: The microcalorimeter sample-stage is integrated into the SWAXS-camera (S3-MICRO) which is equipped with two independent linear 1D-PSD detectors for simultaneous SAXS and WAXS measurements, respectively. Dimensions approximately: 80 x 15 x 40 cm.
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Figure 1. The MICROcaliX system from Hecus.
Detail of the microcalorimeter sample stage: Capacity: 20 ìl in 1.5 mm quartz-capillaries. Max. heating-rate: 5°C/min. Max. temperature-range: -30 to 200°C. Dimensions of the block: 4.5 x 6.5 x 22 cm.
Measurements and Results
DSC/SWAXS scan of AMF: Starting at 80°C (where the sample was equilibrated for 10 min in order to erase any crystal memory) the sample was first cooled down to -8°C with a scan rate of -3°C/min. After equilibration for 20 min at this temperature the sample was heated up to 50°C with a scan-rate of 2°C/min. Exposure time for SWAXS-spectra was 15 s per frame (4 frames/min) throughout the entire scan.
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The corresponding signal of the microcalorimter (blue) is displayed in the middle between the SAXS and WAXS-plots and shows various endo- and exo-thermic transitions at temperatures indicated in the plot (the sample-temperature during the scan and equilibration is given in red). The respective d-values of the Bragg-peaks originating from the lattice structure of the sample are also indicated in the SAXS and WAXS patterns.
Summary
As it can be seen from the DSC-signal and SWAXS-curves, the crystallization and melting transitions are not “symmetric”, i.e. during melting the structure undergoes an additional transition not present in the crystallization process.
Authors - M.Kriechbaum, P.Herrnegger, S.Bodner and P.Laggner Source - Hecus
For more information on this source, please visit Hecus.