Presentation Title

Rate of Crystal Formation and its Impact on Purity: An Investigation Using Scanning Electron Microscopy and X-Ray Spectroscopy

Presenter Information

Parta Ansari Pirsaraei

Location

House of Learning Library, 3rd floor

Start Date

18-3-2016 12:00 PM

End Date

18-3-2016 6:00 PM

Abstract

A crystal has its constituents arranged in an ordered structure. Textbooks state that crystals formed more slowly have fewer impurities than those generated rapidly. Typically, purity is analyzed by atomic absorption spectroscopy: a slow, destructive technique that prevents imaging. Here, one goal is to determine if crystals that form slowly are indeed purer than those formed rapidly. Another goal is to assess if the elemental detector on a Scanning Electron Microscope (SEM) could be used to evaluate crystal purity quickly, non-destructively, and while allowing crystal visualization. Dimethyl terephthalate, calcium chloride, and anhydrous ethanol solution were recrystallized from boiling at 3 cooling rates: to a “benchtop” room temperature (slower crystal formation) to a room temperature water bath (more rapid crystal formation), and to an ice-water bath at ~10°C (most rapid crystal formation). Crystals were placed inside the SEM for examination. Elemental analysis was used to assess purity, and crystals were compared visually. Recrystallizing at room temperatures usually generated an impure product with fewer, but well-defined crystals, whereas the colder temperature created a purer product with more, but less-defined crystals. Purity results did not match those predicted, while those for crystal morphology did. The elemental detector was an excellent tool for this work. This research is important, since quantitative SEM of crystals has potential use in the pharmaceutical industry.

Department

Biological Sciences

Faculty Advisor

Cynthia Ross Friedman

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Mar 18th, 12:00 PM Mar 18th, 6:00 PM

Rate of Crystal Formation and its Impact on Purity: An Investigation Using Scanning Electron Microscopy and X-Ray Spectroscopy

House of Learning Library, 3rd floor

A crystal has its constituents arranged in an ordered structure. Textbooks state that crystals formed more slowly have fewer impurities than those generated rapidly. Typically, purity is analyzed by atomic absorption spectroscopy: a slow, destructive technique that prevents imaging. Here, one goal is to determine if crystals that form slowly are indeed purer than those formed rapidly. Another goal is to assess if the elemental detector on a Scanning Electron Microscope (SEM) could be used to evaluate crystal purity quickly, non-destructively, and while allowing crystal visualization. Dimethyl terephthalate, calcium chloride, and anhydrous ethanol solution were recrystallized from boiling at 3 cooling rates: to a “benchtop” room temperature (slower crystal formation) to a room temperature water bath (more rapid crystal formation), and to an ice-water bath at ~10°C (most rapid crystal formation). Crystals were placed inside the SEM for examination. Elemental analysis was used to assess purity, and crystals were compared visually. Recrystallizing at room temperatures usually generated an impure product with fewer, but well-defined crystals, whereas the colder temperature created a purer product with more, but less-defined crystals. Purity results did not match those predicted, while those for crystal morphology did. The elemental detector was an excellent tool for this work. This research is important, since quantitative SEM of crystals has potential use in the pharmaceutical industry.