MICROSOCPY AND IMAGING
identifi ed by their Raman spectra as TiO2 in the USA candy (red in Figs. 2B and
2D) and calcium carbonate (CaCO3 ) in
the EU candy (blue in Figs. 2C and 2D). Raman spectroscopy can even diff erentiate crystal forms of TiO2
; T e print in the
USA candy consists of anatase (Figs. 2B and 2D).
SUMMARY As clearly shown in the experiments above, it is possible to generate sharp, exquisitely detailed Raman images of samples with roughly textured and very contoured surfaces. Over a large area of
Fig.2 A
C B C Ievgeniia Iermak – WITec D
Topographic Raman imaging of candy coatings. (A): Photograph of the investigated candy. (B): Topographic Raman image of the print on the candy produced for the USA. (C): Topographic Raman image of the print on the candy produced for the EU. (D): The “S” prints are colour coded according their Raman spectra, revealing that the white pigment is TiO2 CaCO3
in the USA, and in the EU. Measurement by Dr
Topographic Raman imaging of a nutritional supplement tablet. (A): Sample topography of the untreated tablet. Scan area: 10 x 3mm². (B): Topography of the abraded tablet. Scan area: 5 x 1.5mm². (C): Topographic Raman image of the abraded tablet, revealing the distribution of the tablet’s ingredients on the rough sample surface: magnesium compound (red), calcium compound (CaCO3
,
green), binder (blue) and emulsifi er (yellow). Pink: fl uorescence. Scan area: 5 x 1.5mm². Measurement by Andrea Richter – WITec
interest, the TrueSurface module for alpha300 microscopes can ensure a consistent focus while acquiring a Raman spectrum from every image pixel. T e visualisation that results can show researchers precisely which compounds are present, their distribution and the relationship between chemical and structural properties. For nutrition and food scientists, this sort of insight is invaluable and the convenience with which it can be obtained makes the module a valuable tool that can off er great utility in their laboratories.
Damon Strom & Eleni Kallis are with WITec.
raman.oxinst.com
www.scientistlive.com 55 A
Fig.1
B
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