Search Research Equipment

Description

Raman is a spectroscopic technique based on light interacting with chemical bonds in a product resulting in specific vibrations. Confocal Raman imaging allows the visualization of the spatial distribution of chemical constituents within a sample in the X-Y-Z plane. The obtained hyperspectral image/cube contains full spectral information in each pixel of the image corresponding to a unique spatial location on the sample. Use of specific peaks or chemometric tools like K-mean clustering or Multivariate Curve Resolution enables the elucidation of known and unknown compounds. Raman imaging is widely used to study different types of materials e.g., foods, packaging, pharmaceutical, cosmetics, material science, etc.

Fig 1: Normalized MCR concentration maps of a spread, showing the spatial distribution of the individual compounds SF, water, solid fat and emulsifier

Figure 2: Packaging foil after K-mean clustering analysis of the Raman image showing the location of the different layers in two batches (left a and b) and the heterogeneous and homogeneous distribution in the LDPE layer in the different batches (right a and b) 

Technical Details

WITec Alpha 300 R+ equipped with:

• a Zeiss upright microscope
• 532 nm laser with (EM)CCD detector, gratings 600 and 1800 lines/mm 
• 785 nm laser with CCD detector, gratings 600 and 1200 lines/mm
• pinhole fibers with diameter 25, 50 and 100 µm
• a home-made cooling/heating system, sample temperature range ~ 5 - 30 °C
• objectives as stated in table 1 
• theoretical lateral resolution with 532 nm laser and objective with NA of 1.4 is 230 nm

Table 1: Available objectives

Applications

Raman spectroscopy can be used for:

•  identification of compounds
•  quantification of compounds

Raman spectroscopic imaging can be used for:

•  structure elucidation of the distributions of compounds in various products
•  depth profiling
•  stress measurements

Complementary Techniques

FTIR imaging