Applications of FTIR Spectroscopy

1 Listicle Applications of FTIR Spectroscopy Alex Beadle Fourier transform infrared (FTIR) spectroscopy is one of the most popular analytical techniques used by scientists today.1 Differentiated from more general IR spectroscopy techniques through its use of an interferometer – a helium–neon laser plus accessories that can act as an internal reference for each scan – the FTIR technique provides very accurate and stable readings of a given sample’s chemical composition.2 Moreover, FTIR is a very flexible technique that can be performed either on the workbench or using a handheld FTIR spectrometer for in-field measurements. FTIR can also easily be combined with other analysis methods, including gas chromatography (GC-FTIR) and thermogravimetric analysis (TGA-FTIR), to gain even more detailed information about a given sample. In this list, we consider some of the diverse subject areas in which FTIR spectroscopy has become an indispensable tool. Environmental analysis The flexibility of FTIR means that the technique can be easily deployed to test for the presence of pollutants in solid, liquid, gaseous and biological samples, making it well-positioned for general environmental analysis. For nearly two decades, FTIR has been one of the most popular techniques used by scientists looking to analyze microplastics in the environment.3 A recent review of articles published between January 2010 and December 2019 found more than 400 papers focusing on FTIR in microplastics research.3 Included in this review were cases of FTIR being used to identify microplastic pollution in sediment, dust and a variety of different water sample types. Beyond simple identification, alternative techniques have been developed for more detailed studies of microplastic pollution. FTIR in combination with an attenuated total reflection (ATR-FTIR) sampling technique is used to assess the degree of weathering on microplastic particles.4 A novel imaging FTIR method has recently been developed for the quantification of microplastics in the guts of fish.5 Additionally, the US Environmental Protection Agency recommends the use of FTIR for air pollution assessments, as the technique is capable of detecting and measuring more than 100 of the hazardous air pollutants (HAPs) listed in the US Clean Air Act of 1990.6 APPLICATIONS OF FTIR SPECTROSCOPY 2 Listicle Food and beverage analysis FTIR is used extensively throughout the food and drink industry to ensure that consumable products comply with relevant government standards and have not been adulterated prior to sale. The rapid, inexpensive and nondestructive nature of FTIR analysis is a significant advantage for the analysts who use it to, among other things, screen for the presence of heavy metals in green tea, antibiotics in eggs and mycotoxins in agricultural products.7 In addition to ensuring that foods are free from harmful contaminants, many countries also have legislation that mandates food and dietary supplement manufacturers to declare the amount of trans fat present in their products. ATR-FTIR is one of the rapid determination techniques that has risen in favor over the past several years for this application.8 Several high-profile cases of food fraud, such as the Chinese milk scandal of 2008 and the EU horsemeat scandal in 2013, have highlighted the need for rapid and reliable methods that are capable of detecting incidents of adulteration or false labeling. FTIR is routinely used for this purpose for premium foodstuffs, including extra virgin olive oil, honey and beef, but has also been implemented more recently in authenticity tests for herbs and spices such as oregano and saffron.9 Forensic science In a forensic investigation, even the smallest amount of information gleaned from seized materials or trace evidence could become the breakthrough that investigators need to solve a case. While FTIR instruments may not be the most commonplace analytical instrument in forensic laboratories, a review of published forensic case studies shows that FTIR imaging techniques are still being utilized regularly for the identification and compositional analysis of different sample types.10 This includes the analysis of animal tissues, pharmaceuticals and dietary supplements and unknown trace powders and solutions that may be present at or seized from a place of interest. Outside of the traditional forensic laboratory, a handheld ATR-FTIR apparatus can be used at a crime scene in order to assess evidence rapidly that might otherwise be difficult to sample. For example, ATR-FTIR has been used in the identification and discrimination of body fluid stains present at crime scenes, generating data that can be used to deduce a person’s blood type, age, gender and race.11 ATR-FTIR can also be used for postmortem investigations, typically for diagnosing ambiguous deaths caused by extreme weather conditions, fatal anaphylactic shock or diabetic ketoacidosis.11 Medicine and pharmaceuticals Since the method was first developed, FTIR has been an indispensable technique for the study of organic molecules. Its sensitivity in detecting changes in functional groups, especially in molecules such as lipids, proteins and nucleic acids, has precipitated the extensive use of FTIR in medicine and the biomedical fields.12 Literature reports indicate the continued use of FTIR in the diagnosis of lung, breast, skin, cervical and colon cancers, as well as in the screening of biofluids for biomarkers indicating chronic disease.12,13 For similar reasons, the pharmaceutical industry has also been quick to adopt FTIR as a low-cost, high-accuracy, precision technique for the analysis of pure pharmaceutical drugs and drugs in different dosage forms.14 In addition to investigating drug dosing, FTIR can be used to ensure the authenticity of drugs. Current estimates from the World Health Organization suggest that around 10% of medicines worldwide are low-quality or have been falsified, with much of this tampering concentrated in low- and middle-income countries.15 In a similar APPLICATIONS OF FTIR SPECTROSCOPY 3 Listicle fashion to how FTIR is deployed in suspected cases of food fraud, the technique can be used to assess the drug content of medicinal products rapidly. While other methods of analysis, such as high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy have also been used for drug authentication, the relative affordability and simple sample preparation requirements of FTIR make the technique especially suited to detecting substandard medicines in poorer nations that may be at higher risk for these practices.15 Materials science With the increasing demand for high-performance batteries capable of powering next-generation electric vehicles, materials scientists are eager to find new and more efficient ways of performing materials analysis and electrochemical studies that can help to improve the scientific understanding of battery function. While the individual components of a battery can be studied separately, both before and after use, there is a wealth of important information that can be gained through operando or in situ study. Using FTIR-based methods, scientists are able to assess the degradation processes that occur in batteries during operation, as well as track important physical and electrochemical changes. Crucially, unlike other popular techniques such as x-ray diffraction (XRD), FTIR is a surface-sensitive technique, which makes it particularly well-suited to investigating structural changes on battery interfaces.16 FTIR is also relied upon for more traditional materials analysis, such as defects or inclusions within polymers and rubbers.17 Art The surface sensitivity of FTIR, as well as its non-destructive nature, is also a significant contributor to the popularity of the technique in fine art and archeological artifact conservation. FTIR analysis can provide conservators with detailed information about the materials that they will be working with during a conservation or restoration attempt. For this reason, FTIR is frequently employed to characterize old varnishes and paint layers on historic paintings, so that the most appropriate cleaning solvents can be selected.18 Such investigations can also tell conservators more information about the artifacts with which they are working. For example, FTIR has been used to study paintings by Edvard Munch belonging to the National Museum of Art in Norway, in order to improve understanding of the controversial varnishing techniques reported to have been used on the paintings by previous conservators.19 Conclusion It is difficult to find a discipline that has not made extensive use of the FTIR technique. From historic artifacts to studying the very food that we eat, FTIR is at the forefront of modern science and technology. With more time and further investigations, FTIR will continue to help scientists to make the breakthroughs that shape the world around us. APPLICATIONS OF FTIR SPECTROSCOPY 4 Listicle References 1. Thain S. IR spectroscopy and FTIR spectroscopy: How an FTIR spectrometer works and FTIR analysis. Technology Networks. Published August 16, 2022. Accessed June 9, 2023. http://www.technologynetworks.com/analysis/articles/ir-spectroscopyand-ftir-spectroscopy-how-an-ftir-spectrometer-works-and-ftir-analysis-363938 2. Faghihzadeh F, Anaya NM, Schifman LA, Oyanedel-Craver V. Fourier transform infrared spectroscopy to assess molecular-level changes in microorganisms exposed to nanoparticles. Nanotechnol Environ Eng. 2016;1(1):1. doi:10.1007/s41204-016-0001-8 3. Veerasingam S, Ranjani M, Venkatachalapathy R, et al. Contributions of Fourier transform infrared spectroscopy in microplastic pollution research: A review. Crit Rev Environ Sci. 2021;51(22):2681-2743. doi:10.1080/10643389.2020.1807450 4. Campanale C, Savino I, Massarelli C, Uricchio VF. Fourier transform infrared spectroscopy to assess the degree of alteration of artificially aged and environmentally weathered microplastics. Polymers. 2023;15(4):911. doi:10.3390/polym15040911 5. Uurasjärvi E, Sainio E, Setälä O, Lehtiniemi M, Koistinen A. Validation of an imaging FTIR spectroscopic method for analyzing microplastics ingestion by Finnish lake fish. Environ Pollut. 2021;288:117780. doi:10.1016/j.envpol.2021.117780 6. Lay LT. United States Environmental Protection Agency Fourier transform infrared spectroscopy test program for emissions measurement. Office of Scientific and Technical Information. Published December 31, 1994. Accessed June 9, 2023. https://www. osti.gov/biblio/197422 7. Qi W, Tian Y, Lu D, Chen B. Research progress of applying infrared spectroscopy technology for detection of toxic and harmful substances in food. Foods. 2022;11(7):930. doi:10.3390/foods11070930 8. Mossoba MM, Milosevic V, Milosevic M, Kramer JKG, Azizian H. Determination of total trans fats and oils by infrared spectroscopy for regulatory compliance. Anal Bioanal Chem. 2007;389(1):87-92. doi:10.1007/s00216-007-1262-7 9. 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J Biophoton. 2014;7(3-4):153-165. doi:10.1002/jbio.201400018 14. Fahelelbom KM, Saleh A, Al-Tabakha MMA, Ashames AA. Recent applications of quantitative analytical FTIR spectroscopy in pharmaceutical, biomedical, and clinical fields: A brief review. Rev Anal Chem. 2022;41(1):21-33. doi:10.1515/revac-2022-0030 15. Lawson G, Ogwu J, Tanna S. Quantitative screening of the pharmaceutical ingredient for the rapid identification of substandard and falsified medicines using reflectance infrared spectroscopy. PLoS One. 2018;13(8):e0202059. doi:10.1371/journal. pone.0202059 16. Amaral MM, Real CG, Yukuhiro VY, et al. In situ and operando infrared spectroscopy of battery systems: Progress and opportunities. J Energy Chem. 2023;81:472-491. doi:10.1016/j.jechem.2023.02.036 17. Wilhelm P. Applications of FT-IR microscopy with materials analyses. Micron. 1996;27(5):341-344. doi:10.1016/S0968- 4328(96)00020-0 18. Al-Emam E, Beltran V, De Meyer S, et al. Removal of a past varnish treatment from a 19th-century Belgian wall painting by means of a solvent-loaded double network hydrogel. Polymers (Basel). 2021;13(16):2651. doi:10.3390/polym13162651 19. Ford T, Rizzo A, Hendriks E, Frøysaker T, Caruso F. A non-invasive screening study of varnishes applied to three paintings by Edvard Munch using portable diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Herit Sci. 2019;7(1):84. doi:10.1186/s40494-019-0327-1