production
Fig. 1d.
Corresponding Raman spectra
Fig. 1b.
Zoom-in of the marked area in Fig 1a, 1x1 mm, 150 x 150 pixels resolution. Figs. 1b and 1c show such zoomed in images of the marked areas. In Fig. 1b the scan range was 1 x 1mm, in Fig. 1c it was 80 x 80 µm, at 150 x 150 pixels. In a second experiment, a depth profile of a capsule within a scan range of 50 x 12 µm and 100 x 80 pixels (=8000 spectra) was acquired. In both cases, a 532 nm frequencydoubled Nd:Yag laser was used for excitation. The acquisition time for each spectrum was 50 ms. Figure 2, top, shows the depth profile of the capsule with the distribution of agent (red and blue) and a coating (green) surrounding the capsule to ensure easy swallowing. On the bottom in fig. 2 the corresponding spectra are shown. The software also offers the possibility to measure distances within the image. In this case, the coating of the capsule is around 2 µm thick.
Fig. 2.
Raman depth profiling image (top) and Raman spectra (bottom) of a capsule surrounded by a coating
Conclusion With its imaging and depth profiling capabilities, Confocal Raman Microscopy enables the visualization of drug distribution in a variety of substrates.
Fig. 1c.
Zoom in of the marked area in Fig 1b, 80 x 80 µm, 150 x 150 pixels
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