Raman instrumentation

Similar to IR sensors, process analysis is the prevalent application area. Due to the applicability of standard VIS instrumentation, Raman probes have been used for more than two decades65, 66. Typically, Raman probes are applied where near-IR probes fail and hence are in direct competition to mid-IR probes. 

Having seen the number of papers devoted to bioprocess analyses utilizing vibrational spectroscopy, it cannot be considered an experimental tool any longer. Manufacturers are responding to pressure to make their instruments smaller, faster, explosion-proof, lighter, less expensive, and, in many cases, wireless. Processes may be followed in-line, at-line, or near-line by a variety of instruments, ranging from inexpensive filter-based to robust FT instruments. Raman, IR, and NIR are no longer just subjects of feasibility studies they are ready to be used in full-scale production. 

M.J. Pelletier, New developments in analytical instruments Raman scattering emission spectrophotometers, in Process/Industrial Instruments and Controls Handbook, G.K. McMillan and D.M. Considine (Eds), McGraw-Hill, New York, 1999. 

Third, the reference method results should be compared with measurements on an equivalent amount of material, particularly if the sample is not homogeneous. In many instruments, Raman spectra are collected only from the sample located in a small focal volume. If that material is not representative of the bulk, then the Raman results will appear to be biased or erroneous. To avoid this problem, multiple sequential spectra are added together to represent an effectively larger composite sample. Alternatively, a larger area could be sampled if the instrument design permits it. If it were desired to study within-sample inhomogeneity, short acquisition times could be used. 

Pelletier, M.J. New Developments in Analytical Instruments Raman Scattering Emission Spectrophotometers. In McMillan, G.K. Considine, D.M. (eds) Process/Industrial Instruments and Controls Handbook 5th Edition McGraw-Hill New York, 1999 pp. 10.126-10.132. 

Due to recent advancements in instrumentation, Raman spectroscopy has become one of the most powerful tools in medical research. Such advancements include development of new lasers, FT-Raman spectroscopy, CCD detectors, confocal Raman microscopy, Raman imaging, fiber optic probes, and computer software. In the following, the utility of Raman spectroscopy in medical science is demonstrated by using selected examples. A more complete coverage of the field is found in review articles by Ozaki (32) and Levin et al. (33). 

Instrumentation. Raman spectra were obtained with use of a Spex 40 double monochromator, and a detection system that utilized photon-counting techniques was used in conjunction with a variety of laser lines (Coherent Radiation principally 488.0, 514.5, and 647.1 nm). Powdered samples were loaded into 1 mm i.d. quartz capillaries in the drybox, and the capillaries were sealed temporarily with a plug of Kel-F grease and then drawn and sealed in a small flame outside the drybox. 

Raman microscopes are more commonly used for materials characterization than other Raman instruments. Raman microscopes are able to examine microscopic areas of materials by focusing the laser beam down to the micrometer level without much sample preparation as long as a surface of the sample is free from contamination. This technique should be referred to as Raman microspectroscopy because Raman microscopy is not mainly used for imaging purposes, similar to FUR microspectroscopy. An important difference between Raman micro-and FUR microspectroscopies is their spatial resolution. The spatial resolution of the Raman microscope is at least one order of magnitude higher than the FTIR microscope. 

Nowadays, many analytical laboratories are equipped with an infrared (IR) and a Raman spectrometer, be it a dispersive device or a Fourier transform (FT) instrument. Raman and IR spectra provide images of molecular vibrations that complement each other and thus both spectroscopic techniques together are also called vibrational spectroscopy. The concerted evaluation of both spectra gives more information about the molecular structure than when they are evaluated separately. 

Infrared spectroscopy has long been successfully used to study the structures of solutions and liquids. Since the spreading of laser-Raman instruments, Raman examinations, which were earlier employed to only a limited extent, have become particularly useful supplements of infrared examinations (e.g., ref. [Me 80a]). 

Princeton Instruments. Raman Spectroscopy Basics (online), http / /content.piac-ton.com/Uploads/Princeton/Documents/Library/UpdatedLibrary/Raman Spectroscopy Basics.pdf [accessed March 30, 2012]. 

Mayo, D.W (Ed.), Infrared Spectroscopy I. Instrumentation II. Instrumentation, Raman Spectra, Polymer Spectra, Sample Handling, and Computer-Assisted Spectroscopy (Vol. 1), Bowdoin College, ME, 1994. 

See also Nonlinear Optical Properties Nonlinear Raman Spectroscopy, Applications Nonlinear Raman Spectroscopy, Instruments Raman Optical Activity, Applications Raman Optical Activity, Theory Raman Spectrometers. 

See also Biochemical Applications of Raman Spectroscopy Chiroptical Spectroscopy, Emission Theory Chiroptical Spectroscopy, General Theory Chiroptical Spectroscopy, Oriented Molecules and Anisotropic Systems Electromagnetic Radiation ORD and Polarimetry Instruments Raman Optical Activity, Applications Raman Optical Activity, Spectrometers Raman Spectrometers Scattering Theory Vibrational CD Spectrometers Vibrational CD, Applications Vibrational CD, Theory. 

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