Infrared (IR) Spectroscopy

Many rubbery polymers contain C=C bonds, which means they are alkenes. Thus, we can identify natural and synthetic rubbers by examining the spectra of cis-, trans-, and tri-substituted alkenes.

As forensic analysis continues to advance, such as in the understanding of source identification and analysis of trace quantities of bodily fluids, spectroscopic techniques and machine learning are playing a significant role. Igor K. Lednev, a chemistry professor at the University at Albany, SUNY, in Albany, New York, has been working in this field with his team. The analytical methods currently under investigation include Raman spectroscopy, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, and advanced chemometric classification and analysis methods. We recently interviewed him about his work.

Infrared (IR) spectroscopy can be used to distinguish the spectra of hydrocarbon polymers from one another.

Professor Rohit Bhargava and his team at the University of Illinois, where they have established the Cancer Center at Illinois, are advancing research in tumor microenvironments, using techniques such as high-definition Fourier transform infrared (HD-FT-IR) coupled with machine learning. We recently spoke to Bhargava about this work.

Those inexperienced in using FT-IR spectrometers can encounter problems when measuring spectra. This article discusses several main issues that most users experience while using FT-IR spectrometers and how to remedy each problem.

Here, we finish a discussion of the spectrum of polyethylene (PE) and explore how different PE syntheses produce materials with different physical and spectroscopic properties.

Peak shifts in infrared spectra may occur for many reasons other than structural changes on the molecular or unit cell level. Here, we discuss several examples.

Igor K. Lednev at the University at Albany SUNY in New York explains advances in forensic analysis using a variety of chemometrics techniques to classify ATR FT-IR and Raman spectra of bodily fluids.

Infrared nanoscopy is a valuable new spectroscopy tool for exploring the nanoscale of materials science. Mun Seok Jeong of Sungkyunkwan University in Korea explains.

Inline FT-NIR and offline terahertz Raman imaging analysis are used to characterize active pharmaceutical ingredient (API) crystallinity and to monitor different solid physical states of the API, to control process parameters of hot melt extrusion.

Resonant SEIRA overcomes the limitations of traditional Fourier transform infrared (FT-IR) spectroscopy for minute sample sizes of relatively low absorptivity. Frank Neubrech of Heidelberg University is exploring resonant SEIRA in applications such as monitoring dynamic processes and hyperspectral infrared chemical imaging.

Polymers contain practically every infrared functional group imaginable. Now that we understand infrared functional groups from previous articles, it is time to look at the spectra of polymers in greater detail.

We show how FT-IR may be used for quality control analysis of natrii sulfas, a transparent crystalline material used in natural medicine that primarily contains sodium sulfate decahydrate, crystallized from sulfate minerals.

Determining the components in a mixture can be a significant challenge in infrared spectroscopy, but spectral subtraction can help. We show the proper way to perform spectral subtraction, and the pitfalls to avoid.

Fran Adar is the winner of the 2021 Gold Medal Award from the New York and New Jersey Society of Applied Spectroscopy (SAS).

One of the biggest practical limitations of infrared spectroscopy is its difficulty in analyzing mixtures. Infrared library searching can help, but it must be done right.

The application of data mining combined with data fusion of Raman and mid- infrared spectra was studied to improve discrimination ability for modeling the geographical origins of rice.

This guide includes many terms related to infrared instrumentation, sampling, measurement techniques, basic nomenclature and concepts, data processing, and applications of infrared instrumentation. In addition, this guide includes some data processing terms, a few statistical data analysis terms, and the essential chemometric terms for typical data preprocessing and calibration.

Jason R. Dwyer of the University of Rhode Island discusses the application of nanopore sensors to the analysis of natural and synthetic oligosaccharides and polysaccharides.

Integrating peak position, height, and width information is important to properly interpret infrared spectra. But do you understand why peak heights and widths vary? We explain.

Articles in this column have addressed five main areas: theory, functional groups containing the C-H bond, those containing the C-O bond, those with the C=O bond, and those with organic nitrogen compounds. Here, we review the concepts.

We review one final organic nitrogen functional group, representing explosive compounds. This is the nitro group, which requires a different set of interpretation rules.

Here we conduct an evaluation of significant operational parameters of IR microscopy for accurately determining the size of microplastics, with the overarching goal of outlining performance parameters that will help in the standardization of microplastics analysis.

Measurements of the optical proper ties of a ceramic material, Z93, which is in current use on the International Space Station (ISS), reveal why this material is successful for thermal control in the ISS implementation, and also point to potential future material design improvements.

Spectroscopic ellipsometry, correlated with UV-vis-NIR spectroscopy, is used to determine the optical constants of thin films, such as in GexSb40-xSe60 chalcogenide glass.

Portable spectroscopic instruments have not had significant visibility within the scientific community compared with, for instance, the current generation of high-performance laboratory mass spectrometers.

In celebration of Spectroscopy’s 35th Anniversary, leading spectroscopists discuss important issues and challenges in analytical spectroscopy.

Here, we continue our examination of the infrared (IR) spectra of organic nitrogen compounds with imides, which are a common chemical intermediate. IR can be used not only to identify imides, but also to distinguish between straight chain and cyclic imides. We explain how.