Infrared (IR) Spectroscopy

In this study, the measured spectra of acetic anhydride, acetic acid, salicylic acid, and aspirin are used for in situ monitoring of the progression of aspirin synthesis in a reaction system. Traditional methods such as HPLC and titration ultraviolet (UV) absorption are not optimal for such real-time monitoring because of long analytical times and complicated procedures. ATR-FT-IR offers an alternative solution that overcomes the shortcomings of traditional techniques.

FT-IR offers an alternative method for the quantification and classification of lignocellulose in biofuel pellets, based on determination of cellulose, hemicellulose, and lignin content. The IR spectroscopic evaluation presented here provides an understanding of the pretreatment and storage of biofuel pellets.

Selecting the correct basis set is essential for enhancing accuracy of DFT simulations. Here, the effects of five basis sets on the theoretical frequencies and calculated infrared intensities are compared to predict the molecular structural and vibrational properties of the triclosan. The demonstrated methods can help provide a benchmark for studying the pollution mechanisms and ecological effects of antibacterial products like triclosan.

By extracting the RGB, HSI, and grayscale information from a spectral range of 400–1100 nm and comparing the spectral features of sound and bruised peaches, the authors provided a classification system and theoretical basis for online fruit bruise detection.

IR absorption spectroscopy technology can solve the problem of line aliasing in gas detection. Here, continuous wavelet transform was used in time-frequency analysis to improve spectral component identification and quantitative detection of gases.

Professor Martin Zanni, the Meloche-Bascom Professor of Chemistry at the University of Wisconsin-Madison, and his colleagues explored how to resolve diagonal peaks using a polarization scheme that can be implemented in pump-probe beam geometry—not only in two-dimensional infrared (2D-IR) spectroscopy but also in TA spectroscopy. Zanni is the 2022 recipient of the Ellis R. Lippincott Award. This interview is part of an ongoing series of interviews with the winners of awards that are presented at the annual SciX conference, which will be held this year from October 2 through October 7, in the Greater Cincinnati/Northern Kentucky area.

In this second part of this four-part series on spectroscopy instrument components, we take a closer look at optical components or subassemblies used for vibrational spectroscopy instruments.

An examination of polymers with C-O bonds, focusing on the spectra of polyvinyl alcohol, cellulose, starch, and copolymers.

Our annual review of new products for atomic and molecular spectroscopy, including details by category and highlights of overarching trends.

Controlling methane is one of the highest-impact ways to reduce climate impacts, so its accurate measurement is essential. Spectroscopy offers valuable tools for this task.

Spray paint is often used by vandals for creating graffiti, as well as for criminals to leave signs, messages, and blots to conceal the left traces at the scene of their efforts. Rajinder Singh and his colleagues in the Department of Forensic Science at Punjabi University (Punjab, India) have used attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy for nondestructive analysis of 20 red spray paints of different manufacturers, which could possibly be encountered at a crime scene, particularly in case of vandalism. Singh spoke to Spectroscopy about the findings, and the paper that resulted from their efforts.

Epoxies are perhaps the most economically important functional group of polymers. We explain how to interpret their spectra.

High-performance instrumentation requires many critical components. We focus here on energy sources, lasers, and detectors.

The Covid-19 pandemic has led to extraordinary developments of both testing methods and vaccines. Can spectroscopy play a role in next-generation testing for Covid and other pathogens?

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.