Fourier Transform Infra-Red Spectroscopy (FTIR) Principle of Operation FTIR allows for the vibrations present in bonds between atoms and functional groups in molecules to be examined in a wide variety of materials. FTIR spectroscopy operates on the simple principle that materials will interact to absorb light more strongly when there is an existing mechanism in the material to consume the energy of that light. Infra-red light happens to have a wavelength and energy that corresponds well with the vibrations of individual atoms across molecular bonds, especially in organic molecules. Each type of bond has its own unique set of vibrations, including stretching, rotation, rocking, and scissoring. Each of these motions has a differing energy, based on the strength of the bond and the chemical environment in the molecule and material. FTIR spectroscopy creates a broad range of IR wavelengths that cover the vast majority of these transitions. The sample is then exposed to the IR light, and the remaining signal is collected by a high sensitivity detection element. The variations in the overall intensity at the detector over a known time is then mathematically manipulated, using Fourier Transforms, and the time data is converted into frequency data. Since each type of molecular vibration has its own range of frequencies, the known frequencies observed in the sample can be interpreted to give a 'fingerprint' for the types of molecular bonds observed in the sample. Using this information a material can be identified, or at the very least classified based on the unique combinations of molecular building blocks identified with the spectrophotometer. Advantages: FTIR can be used in a wide variety of applications, as many types of materials will show varied and active absorption in the wide range of wavelengths used in the instrument. The primary use of the instrument is as a diagnostic to identify organic compounds. Because of the simple atomic variety present in most organic compounds (most organics consist of only five of the most common, light elements), gaining structural information about a molecule is incredibly valuable. Using FTIR both naturally occurring and man-made organic compounds can often be classified. Paints and coating can be differentiated, letting you know if there was simple latex or a more durable urethane used in an application. An organic foulant can be determined as being rich in proteins or composed of simple sugars. An unknown polymer can be classified, and in some cases identified. Our FTIR also possesses a fully capable microscope that can perform FTIR spectroscopy on particles at or below fifty microns in size. This allows for the powerful spectroscopic techniques to be applied to samples that are being examined with either SEM or PLM, allowing identification of that unknown synthetic fiber with chemical as well as optical information, or the determination if a small flake of material in a vial is from oxidized product, or represents a contaminant. IR analysis can generally be performed on nearly any type of material, solids can be directly or indirectly examined as is or with preparation. Liquids and solvents can be examined, and mixtures can either be examined as is, or separated chemically and individual members examined. Using a host of beam manipulation techniques, it also becomes possible to look at unusual or very fine samples, examining a ten micron fouling layer on the surface of a product, or examining an oily residue on the surface of a door or metal part. Limitations: The primary complication in using FTIR analysis is the fact that it often offers too much information. Due to the fact that the technique reveals information about almost all of the bond motion transitions present in the sample, spectra from either very large molecules, co-polymers, or mixtures can rapidly become very difficult to interpret. Due to the fact that chemical environment can impact the frequencies of many peaks, often in these cases peaks can begin to become less unique, further complicating the analysis. Less complicated molecules can also be challenging, as the instrument does not inform with regards to molecular weight or size, hexane and octa-decane will still give relatively similar spectra. While the presence of a highly tuned micro-FTIR allows for small particles or phases to be examined, the sensitivity of the instrument is not completely comparable to GC or HPLC techniques. Using the information from an FTIR analysis can often greatly increase both the accuracy and utility of additional organic analyses, but it doesn't completely replace them. Finally, the presence of a large amount of carbon black, dispersive metallic or inorganic material, or water will often either disperse or absorb a great deal of the sample signal. There are often ways to work around these concerns, but from time to time, these factors will align to make a sample very difficult to effectively analyze using this technique. The Power of FTIR: The FTIR allows for the identification and classification of a wide variety of organic materials, as well as some inorganics and mineral species. Using FTIR in combination with PLM, SEM, and EDX spectroscopy allows for an extremely wide variety of materials to be analyzed and identified. With the power of microscopic FTIR analysis, even small contaminants and particles can be non-destructively identified and examined, often in their original state, without disturbing the materials. Leveraging the experience of our analytical staff with the variety of analytical methods allows for the greatest possible chance that FTIR analysis can remove the unknown from any client's problem situation.

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