Column: IR Spectral Interpretation Workshop

, is the founder and CEO of Big Sur Scientific, a maker of portable mid-infrared cannabis analyzers. He has over 30 years experience as an industrial infrared spectroscopist, has published numerous peer-reviewed papers, and has written three books on spectroscopy. As a trainer, he has helped thousands of people around the world improve their infrared analyses. In addition to writing for Spectroscopy, Dr. Smith writes a regular column for its sister publication Cannabis Science and Technology and sits on its editorial board. He earned his PhD in physical chemistry from Dartmouth College.

Articles

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.

The Infrared Spectra of Polymers IV: Rubbers

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

The Infrared Spectra of Polymers III: Hydrocarbon Polymers

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.

The Infrared Spectra of  Polymers II: Polyethylene

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.

The Infrared Spectra of Polymers, Part I: Introduction

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.

Spectral Subtraction

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.

Library Searching

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.

The Grand Review II: Why Do Different Functional Groups Have Different Peak Heights and Widths?

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.

The Grand Review I: Why Do Different Functional Groups Have Different Peak Positions?

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

Organic Nitrogen Compounds X: Nitro Groups, An Explosive Proposition

Here we delve into the interpretation of another organic nitrogen compound, known as polyurethane, a ubiquitous polymer used for wood finishes and foam rubber.