Raman spectroscopy originated in 1928, when Sir C.V. Raman discovered the scattering effect after observing a sample mixture of water and alcohol excited by sunlight. Raman spectroscopy measures the inelastic scattering of light from a monochromatic light source, usually a laser. When photons are absorbed by a sample, the frequency at which they are re-emitted is shifted from the original frequency – this is called the Raman effect. This noninvasive and nondestructive method provides an extremely detailed analysis of cells in their natural state, allowing similar materials to be discriminated.
Confocal Raman microscopy focuses laser light of a selected wavelength on a specific point in the sample, offering the chemical information of particles at a higher microscopic resolution. This point illumination approach minimizes some of the fluorescence and blurring encountered in wide-field techniques where the whole specimen is evenly illuminated. Well suited for pharmaceutical, biological and materials sample analysis, confocal Raman microscopy is commonly used to examine cells, tissues, active pharmaceutical ingredients (APIs), excipients, polymorphs, graphitic materials, as well as polymer-based materials.
The Gateway Analytical lab currently houses a Bruker Optics SENTERRA Raman Microscope with green and red lasers for spectral data collection. A high performance Raman microscope spectrometer, this system contains an internal continuous calibration mechanism that ensures better than 0.1cm-1 accuracy and precision without the need for external standard calibrations. The system also offers Automatic Fluorescence Rejection (AFR) using shifted excitation Raman difference spectroscopy and also provides high performance confocal depth profiling via FlexFocusTM. In addition, the SENTERRA has an open architecture allowing for high lateral resolution imaging for the study of larger samples.