Fourier Transform Infrared (FTIR) Spectroscopy
Fourier transform infrared spectroscopy is an analytical method that is very versatile and has excellent sensitivity. Molecules absorb infrared radiation (heat, thermal energy) in a way that is influenced by the molecular structure. The infrared spectrum readily distinguishes polyethylene from polypropylene, aromatic polymers from aliphatic polymers, and silicone rubber from nitrile rubber, for example. Many scientists refer to the infrared spectrum as a "chemical fingerprint" because, like a personís fingerprint, an infrared spectrum is highly unique.
In our laboratories, the FTIR spectrometer is one of the workhorse instruments. It is also an analytical method that often requires little or no sample preparation. Often, it is possible to obtain a full infrared spectrum non-destructively. So, forensic evidence can be characterized without altering its physical features. And, expensive products and components need not be destroyed as a consequence of the analysis. The infrared spectral method of analysis is a very cost effective approach to quickly obtain a significant amount of objective information about a sample. For many failure analysis projects, verification of the principle constituents of the sample is a critical first step.
What Can FTIR Spectroscopy Do For You?
You can readily compare different batches of raw materials to determine if their overall compositions are the same or not. This same approach can also be used for quality control purposes within a manufacturing facility
Rubber materials, as may be used to make o-rings and gaskets, can readily be identified using FTIR spectroscopy. If you need to figure out what a material is, consider FTIR spectroscopy as an excellent first step.
Polymer Solutions Incorporated can develop and validate custom FTIR methods. We can also use established ASTM or ISO Methods.
View Nathan's FTIR Video
Mass Spectrometry (MS)
Mass spectrometry is an analytical method that provides a spectrum that, when interpreted, reveals the molecular structure of the chemical compound. Molecules are composed of chemical units that are themselves comprised of specific chemical elements. When the molecule is bombarded with high energy electrons, characteristic "functional groups" and molecular fragments are produced. The functional groups and fragments have unique mass to charge ratios. As a result, a chemically interpretable mass spectrum is obtained.
Although a mass spectrum can be obtained for a chemical mixture, most MS analyses are conducted on pure compounds. More often however, the samples we receive in our laboratory are mixtures of many chemical compounds. Accurate and detailed work requires that the mixture be separated into individual chemical compounds. The separation is accomplished by using gas chromatography prior to analysis by the mass spectrometer.
What Can MS Do For You?
Mass spectrometry, especially when coupled with gas chromatographic analysis, is a useful method for identifying contaminants, additives, and residual monomers in polymers, for example.
A worker complained of respritory irritation during a high temperature metal processing operation. Polymer Solutions sent an analytical chemist to the facility, modified the production process slightly so that a gas sample could be collected and returned to the laboratory for testing. The airborne contaminant was conclusively identified. This allowed the clientís industrial hygiene department to initiate the appropriate next steps.
It is common for us to receive various samples, including solvent samples, to perform compositional analysis and verify purity, identify minor constituents, or even contaminants. We donít only do this for clients! We also routinely use the GC-MS method to verify the purity of the solvents we purchase so that we can independently assure that the analysis of our clientís samples will proceed properly.
Residual monomer in polymers is an important characteristic. Depending on the purification methods employed, and also influenced by environmental exposures, residual monomer levels can vary significantly. Residual monomer analysis is performed by Polymer Solutions for products at every stage of their lifecycle; raw material, molded, sterilized, stored, and even as part of failure analysis investigations.
Polymer Solutions Incorporated can develop and validate custom GC-MS methods. We can also use established ASTM or ISO Methods.
View Athena's GC-MS Video
We welcome the opportunity to Partner our Experts with your team. You can call us, toll-free (1-877-961-4341) or visit our web-site and connect with us by e-mail.
In this issue:
There are many spectroscopic methods that are used to answer the question: "What is it?" Spectroscopic methods are well suited for solids, liquids, and gases. If you need to identify a material, a contaminant, a competitorís product, or simply require verification of chemical identity, a spectroscopic method will likely be used.
In this e-Newsletter, we discuss infrared spectroscopy, nuclear resonance spectroscopy, and mass spectrometry.
You can get even more information about these important topics, and others, by visiting our web-site or by talking to one of our Experts.
Bonus Content This Month:
- Three Videos From Our Staff
- "You Provide the Topics"
- "You Provide the Caption" Contest
1. Three Videos From Our Staff
Alan - NMR Video
Athena - GC-MS Video
Nathan - FTIR Video
2. "You Provide the Topics"
We have many topics related to plastic and rubber materials, analysis, government regulations, case studies, expert witness examples, and materials science issues.
Our December 2011 newsletter will be devoted exclusively to topics selected by our readers. Five submissions will be randomly selected and will receive a $25.00 BestBuy gift card.
Submit your topic.
3. "You Provide the Caption" Contest
Provide a caption to the photo shown above.
The winning caption will receive a $35.00 Starbucks gift card! In the next newsletter, the winning caption and the other entries (losers) will be listed.
Submit your entry now. Be creative!
Nuclear Magnetic Resonance (NMR) Spectroscopy
Nuclear magnetic resonance spectroscopy (NMR) is an analytical technique that provides highly detailed information in the form of a spectrum. The constituent atoms must have a magnetic moment to generate an NMR spectrum. Therefore, detailed structural information is obtained for molecules containing hydrogen, carbon, fluorine, silicon, and phosphorus. Although additional atoms can be evaluated, our clients tend to be most interested in these five with proton NMR being most common and carbon NMR being second most common.
When a molecule is exposed to a very strong magnetic field and also to a strong radio-frequency (RF) pulse, a signal is induced in a detector. The signal is highly influenced by the chemical environment of each atom that comprises the molecule. As a result, the spectrum is interpretable based on fundamental principles of chemistry or can be compared with spectral data bases to provide important molecular structure information.
Like other spectroscopic methods, NMR spectroscopy can be performed on pure compounds, polymers, or mixtures. Typically, we determine the presence or absence of specific types of molecules or molecular units.
So, for example, we can determine if a polymer is a copolymer or a terpolymer, can detect trace compounds, or can identify the molecular units that have been used to synthesize a polymer material.
What Can NMR Do For You?
NMR spectroscopy can be used to verify your polymerís chemical composition, repeat units, and branching. Also, end groups can be detected, identified, and quantified. If impurities or additives are of interest to you, the NMR method can also be used with a detection limit of approximately 0.05% or better.
For the purpose of competitor product analysis or the comparison of a "good" and "bad" lot of material NMR is very powerful. For example, we compared the composition of two lots of SBR (styrene-butadiene copolymer rubber) and were able to determine the reason for performance variation. In this case, the amount of styrene and butadiene repeat units was established. Also, the details of the butadiene linkages (cis/trans and 1,2- versus 1,4-) were reported. This level of detail can be applied to your polymer system.
Polymer Solutions Incorporated can develop and validate custom NMR methods. We can also use established ASTM or ISO Methods.
View Alan's NMR Video