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PTR-ToF-MS Coupled with an Automated Sampling System and Tailored Data Analysis for Food Studies: Bioprocess Monitoring, Screening and Nose-space Analysis
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Tracing coffee tabletop traces.

Jork Leiterer1, Franziska Emmerling, Ulrich Panne

  • 1BAM Federal Institute for Materials Research and Testing, Richard-Willstatter-Strasse 11, 12489 Berlin, Germany.

Langmuir : the ACS Journal of Surfaces and Colloids
|June 28, 2008
PubMed
Summary
This summary is machine-generated.

Caffeine crystallization on surfaces forms coffee rings with mixed alpha- and beta-caffeine crystals. Acoustic levitation yields only alpha-caffeine, suggesting surface effects influence crystal polymorphs.

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Area of Science:

  • Materials Science
  • Chemistry
  • Crystallography

Background:

  • Crystallization is fundamental to chemistry, pharmacy, and medicine.
  • Understanding micro- and nanocrystal formation is crucial for various applications.
  • Caffeine-water solutions serve as a model system for studying crystallization.

Purpose of the Study:

  • To investigate caffeine crystallization from aqueous solutions under ambient conditions.
  • To analyze the influence of surfaces versus acoustic levitation on caffeine crystal polymorphs.
  • To explore controlled formation of cocrystals and novel polymorphs.

Main Methods:

  • Evaporation of aqueous caffeine droplets on surfaces (glass, polystyrene, polyester).
  • Analysis of resulting "coffee tabletop" rings using micro focus X-ray beam.
  • In situ synchrotron X-ray diffraction of ultrasonically levitated caffeine droplets.
  • Atomic Force Microscopy (AFM) for nanoscale particle analysis.

Main Results:

  • Stable "coffee tabletop" rings of caffeine crystals formed upon droplet evaporation on surfaces.
  • Both alpha- and beta-caffeine crystal modifications were found, locally separated within the rings.
  • Acoustic levitation resulted in pure alpha-caffeine, without the beta-caffeine polymorph.
  • AFM revealed nanoscale particles in addition to microcrystals.

Conclusions:

  • Surface interactions significantly influence caffeine crystallization, leading to the presence of both alpha- and beta-polymorphs.
  • Acoustic levitation, free from surface effects, yields only the alpha-polymorph.
  • These findings offer new possibilities for controlling the formation of micro- and nanocrystalline materials, including cocrystals and novel polymorphs.
  • The study has implications for pharmaceutical and medical applications requiring precise control over crystal forms.