Special Issues-08-01-2010

Special Issues

Fourier transform–infrared (FT-IR) spectroscopy is convenient and effective for the analysis of foreign matter and other defect analysis. It is widely used to confirm, identify, and detect matter in many applications, including raw materials, medical products, packaging, and coatings.

Infrared (IR) spectroscopy is one of the most versatile and powerful analytical tools that we have today for the characterization and identification of materials. Its strength lies in its ability to handle a broad range of material types, in any physical state, at a wide range of concentrations, and on many occasions, with direct methods of measurement. These strengths are about to be enhanced by the use of instrumentation that utilizes a choice of broadly tunable laser devices, covering the sweet spot of the mid-IR spectrum, the "fingerprint region." These systems currently cover the spectral range of 6–12 ?m (1665–830 cm-1), which provides spectroscopic access to almost all classes of chemical compounds. This article reviews the benefits offered by such a laser system for a wide range of new and challenging applications.

Relying primarily on transmission or reflection techniques, FT-IR microscope and imaging systems often can require tedious sample preparation to obtain representative data from a sample. Conversely, similar to a sample compartment attenuated total reflectance (ATR) accessory, the ATR microscope objective requires no sample preparation as the sample can simply be contacted with the ATR element, or crystal, and then the sample spectra can be collected using the microscope detector. The ATR objectives discussed here are designed to offer simultaneous video observation of the selected sample area during infrared data collection. These ATR objectives provide a unique capability for sample observation and infrared data collection when utilizing a software mapping feature offered with the FT-IR microscopes discussed.

The most popular design of a hollow waveguide consists of silica glass tubing coated internally with silver and silver iodide to create a highly reflective surface. The external surface of the silica glass tubing is coated with an acrylate to enhance waveguide strength. In contrast to traditional mid-IR optical fibers, such as chalcogenide glass, and silver halide polycrystalline fibers, hollow waveguides offer distinct advantages for mid-IR remote sampling. Hollow waveguides, which were recently incorporated into a mid-IR sampling accessory, provide enhanced durability and span the full mid-IR range. This article details the technology and performance of hollow waveguides in the mid-IR spectral region and presents applications in remote sampling.

Establishing credibility and reliability of the information provided by a Fourier transform–infrared (FT-IR) spectrometer is paramount to mitigating risk in the QA/QC laboratory, where simple, fast and error-free analysis of unknown materials or material verification are required. To meet the demands of a modern QA/QC laboratory, FT-IR spectrometers must include capabilities that shift the burden of proving the reliability of the information away from the analyst so they can concentrate on the sample, not on verifying the integrity of the data. Recent design advances in both FT-IR spectrometer hardware and software give users greater confidence by continually reporting instrument status and performance verification, efficiently and effectively running pass–fail tests against specification, and easily adjusting to the degree of variation in a given set of products.

Characterization of trace evidence is an invaluable asset to the forensic scientist in solving crimes. In particular, the characterization needs to be specific enough so that the identification of material collected at a crime scene can be identified forcefully with material collected from a suspect's environment. Colored microscopic fibers can be discovered easily at a crime scene and collected for analysis. The question is what physical tool can be used to characterize these fibers. Fourier transform–infrared (FT-IR) spectroscopy is a well-established method for characterizing trace evidence. In this article, FT-IR, FT-Raman, and dispersive Raman spectra of a series of prepared fibers will be evaluated for their information content.

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Special Issues

August 01, 2010

Click the title above to open the Spectroscopy August 2010 regular issue, Vol 25 No 8, in an interactive PDF format.