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FTIR Spectroscopy: Principles, Applications, and Analysis

What is FTIR Spectroscopy? Principles and Fundamentals

Home By Application AutoChem Applications FTIR Spectroscopy

What is FTIR Spectroscopy? Principles and Fundamentals

FTIR spectroscopy is a widely used analytical technique for reaction monitoring, process development, and continuous manufacturing across the pharmaceutical, chemical, and polymer industries. Fourier Transform Infrared (FTIR) spectroscopy is a vibrational spectroscopy technique that measures how molecules absorb mid‑infrared radiation across the 4000–400 cm⁻¹ range. These absorptions arise from transitions between molecular vibrational energy levels, producing a spectrum that reflects molecular structure, chemical bonds, and functional groups.

Wavenumbers (cm⁻¹), which are linearly proportional to energy, are used to express infrared frequency and provide a direct measure of vibrational energy. Although the underlying physics of infrared absorption is the same for both FTIR and traditional dispersive IR spectroscopy, FTIR differs fundamentally in how spectra are acquired. Instead of scanning one wavelength at a time through a monochromator, FTIR collects all wavelengths simultaneously using an interferometer, generating an interferogram that contains information from the entire spectral range.

A Fourier Transform algorithm converts this time‑domain signal into a frequency‑domain spectrum, producing a characteristic molecular fingerprint more rapidly than dispersive IR. This approach also enhances signal quality and enables a broader range of mid‑infrared applications.

Inline FTIR Instruments for Process Control

System ReactIR 702L, TEMCT

System ReactIR 702L, TEMCT

Improve Reaction Understanding

Compact real-time FTIR analyzer for chemical and pharmaceutical development monitors reaction progression in situ, accelerating process development; track reactants, intermediates, and products to optimize kinetics, mechanisms, and pathways.

For Use In
Laboratory
Software
iC IR
Detector
TE MCT
Optical Range (Base Unit)
4000 - 800 cm-1
Purge Requirement
No
See all features
System ReactIR 701L, LN2

System ReactIR 701L, LN2

Performance Simplified

High sensitivity real-time FTIR analyzer for chemical and pharmaceutical development monitors reaction progression in situ, accelerating process development; track reactants, intermediates, and products to optimize kinetics, mechanisms, and pathways.

For Use In
Laboratory
Software
iC IR
Detector
LN2 MCT
Optical Range (Base Unit)
4000 – 650 cm-1
Purge Requirement
No
See all features
Base Unit HL ReactIR 45P

Base Unit HL ReactIR 45P

Improve Process Efficiency

Rugged real-time FTIR analyzer monitors reaction progression in situ. Enabling processes to be successfully moved from lab to pilot to production, while meeting the stringent safety requirements of equipment used in a hazardous or classified area.

For Use In
Lab, Pilot Plant, or Production
Software
iC IR; iC Process
Detector
DTGS; SE MCT
Optical Range (Base Unit)
4000 – 650 cm-1
Purge Requirement
Yes
See all features

How FTIR Works: The Michelson Interferometer and Fourier Transform

In the classic Michelson interferometer, broadband IR radiation strikes a beamsplitter that divides the energy into two paths: one reflected off a fixed mirror and the other off a mirror moving at a precisely controlled velocity. As the moving mirror changes the optical path difference, the recombined beams generate constructive and destructive interference at the detector. For polychromatic radiation, the detector records a complex waveform, known as an interferogram, that contains contributions from all IR frequencies simultaneously. This signal is then transformed into familiar absorbance-versus-wavenumber spectrum. A reference laser tracks mirror displacement, ensuring precise wavenumber calibration and long-term measurement stability.

The multiplexed measurement provides Jacquinot’s advantage (high optical throughput), Fellgett’s advantage (improved signal‑to‑noise ratio through the simultaneous measurement of all frequencies), and Connes’ advantage (high frequency accuracy derived by laser‑based calibration). Together, these advantages enable FTIR to acquire high‑resolution, high‑sensitivity spectra rapidly, making it ideal for investigating in‑situ chemical processes where fast, information‑rich measurements are essential.

FTIR Sampling Techniques: Transmission, ATR, and In‑Situ Analysis

Transmission FTIR

Transmission FTIR is the classical approach in which infrared radiation passes directly through a sample in a fixed‑path cell, as a thin film, or a KBr matrix pellet. Because the IR beam must traverse the material, transmission measurements require careful control of sample thickness and homogeneity. This technique is well suited for gases, dilute solutions, and thin polymer films but less effective for strongly absorbing or highly scattering media.

Attenuated Total Reflection (ATR)

Attenuated Total Reflection (ATR) overcomes limitations of Transmission FTIR by directing the IR beam into a high‑refractive‑index crystal, typically diamond, silicon, or zinc selenide, where it undergoes multiple internal reflections. At each reflection, an evanescent wave penetrates only a few micrometers into the sample, enabling the analysis of viscous liquids, powders, slurries, and heterogeneous solids with minimal preparation. ATR-FTIR has become the most widely used FTIR sampling technique because it accommodates variable sample thickness, provides excellent reproducibility, and simplifies sample handling and cleaning.

In-Situ FTIR Spectroscopy

In-situ FTIR spectroscopy is widely used in research, early and late development, scale up and reaction optimization. Typically using fiber‑optic ATR probes or flow‑cell interfaces, this technique enables direct measurements inside reaction vessels, pressure reactors, and continuous flow systems. By collecting spectral data under actual process conditions, including temperature, pressure, concentration, and mixing, in-situ FTIR provides real-time insight into reaction kinetics, mechanisms, and defines critical control parameters (CPP) that can be seamlessly transferred to production. The technique can also be used to track reactants, products, and intermediates, monitor conversion and endpoint, and support PAT‑driven process control. These capabilities have made in-situ FTIR a key technology in reaction monitoring platforms such as ReactIR™.

Advantages of FTIR: Speed, Sensitivity, and Spectral Resolution

FTIR spectroscopy offers several intrinsic advantages that make it a powerful analytical technique, particularly where speed, sensitivity, and spectral differentiation are essential.

  • Nondestructive analysis: FTIR is inherently a nondestructive technique, requiring little to no sample preparation while preserving the material for subsequent analyses. In reaction monitoring applications, it provides critical information without disturbing the system under investigation.
  • Rapid data acquisition: Because the entire infrared spectrum is collected simultaneously rather than scanned sequentially, FTIR enables exceptionally fast measurements, often capturing complete spectra in milliseconds, making the technique well suited for real-time monitoring of fast or transient chemical processes.
  • High sensitivity: FTIR’s sensitivity arises from both the multiplex nature of the measurement and the high optical throughput of interferometer‑based instruments. This enables FTIR to detect subtle compositional changes, low‑level impurities, and weak vibrational modes.
  • Excellent spectral resolution: Precise mirror displacement tracking combined with Fourier Transform processing enables FTIR to resolve overlapping absorption bands in complex samples. As a result, the technique is invaluable for characterizing multicomponent systems and distinguishing closely related chemical structures and functional groups.
  • Qualitative and quantitative capabilities: FTIR provides both qualitative and quantitative information. Quantitative measurements are governed by the Beer–Lambert law (A = ε b c), in which absorbance is proportional to concentration. This relationship enables quantification, kinetic profiling, and concentration tracking across a wide dynamic range.

In-Situ FTIR for Chemical Reaction Monitoring and Process Control

in situ ftir for chemcial reaction monitoring and process control

In-situ FTIR has become one of the most powerful process analytical technology (PAT) tools for real-time reaction monitoring, mechanistic understanding, process optimization, and automated process control. Unlike offline sampling and analysis, which provide only discrete snapshots of a reaction at predetermined time points, in-situ FTIR continuously captures spectral data as the chemistry evolves. This time-resolved approach enables direct observation of reagent consumption, intermediate formation, product growth, reaction kinetics, induction periods, and transient species that are often difficult or impossible to detect using traditional analytical methods.

Real-time FTIR systems, such as ReactIR, monitor chemistry directly inside batch reactors using inserted fiber-optic ATR probes or within continuous flow systems via inline flow cells. ATR-based sensors are designed to operate across a wide range of reaction conditions, including broad temperature, pressure, and pH ranges, and can withstand aggressive solvents and reactants. As a result, in-situ FTIR is widely applied to catalytic reactions, polymerizations, crystallizations, reaction optimization studies, and continuous manufacturing processes.

Continuous acquisition of mid-infrared spectra provides rich kinetic and mechanistic information that supports reaction development and scale-up. Data-rich experiments (DREs) generated through real-time FTIR measurements accelerate Design of Experiments (DoE) studies, kinetic modeling, and statistical analysis by reducing reliance on time-consuming offline sampling and sample preparation. Rather than conducting many experiments to understand reaction dependencies, a smaller set of well-designed studies can often provide the information needed to identify reaction-driving factors, determine kinetic parameters, and establish critical process parameters (CPPs).

Advanced chemometric methods can further deconvolute overlapping spectral bands, extract component concentration profiles, and generate robust multivariate models suitable for batch, semi-batch, and continuous manufacturing. When integrated with automated reactors or flow platforms, FTIR functions as a live process sensor, enabling adaptive process control, predictive modeling, recipe refinement, and autonomous closed-loop operation. By transforming reactions into continuous sources of kinetic and mechanistic data, in-situ FTIR enables more efficient, data-driven process development and accelerated optimization workflows.

interpreting ftir spectra in ic ir software

Interpreting FTIR Spectra: Identifying Functional Groups and Fingerprints 

One of the primary applications of FTIR spectroscopy is the identification of functional groups in organic molecules, providing fundamental information about molecular structure and compound class (e.g., esters, carboxylic acids, amides, and ketones). Most functional groups exhibit characteristic absorption bands at specific wavenumbers. These “group frequencies” arise from fundamental stretching and bending vibrations of bonds such as O–H, N–H, C–H, C=O, C=C, C≡N, and C≡C. Because these vibrations consistently appear within defined spectral regions, FTIR spectra can be used to determine whether key functional groups are present. For example, O–H stretches typically appear between 3400 and 3650 cm⁻¹, carbonyl (C=O) stretches between 1670 and 1780 cm⁻¹, alkene (C=C) stretches near 1640 to 1680 cm⁻¹, and nitrile (C≡N) stretches around 2210 to 2260 cm⁻¹.

In addition to these functional group frequencies, the fingerprint region (approximately 1500 to 600 cm-1) contain absorption bands arising from complex bending modes, skeletal vibrations, and single‑bond stretches such as C–O, C–C, and C–N. Because these features are highly sensitive to subtle structural differences, this region provides a distinctive spectral pattern for each molecule. As a result, the fingerprint region is often used to confirm molecular identity by comparing an unknown spectrum with reference spectra.

Comprehensive FTIR spectral interpretation combines the analysis of characteristic functional-group absorptions with the unique features of the fingerprint region to identify compounds, confirm molecular structure, differentiate closely related species, and monitor chemical transformations. In reaction monitoring applications, changes in peak position, intensity, and shape can also provide valuable information about reaction progress, intermediate formation, and product generation.

Infrared Radiation Sub-Region Comparison

RegionWavenumber Range (cm⁻¹)Wavelength Range (µm)
NIR12,800 – 4,0000.78 – 2.5
MIR4,000 – 4002.5 – 25
FIR400 – 1025 – 1000

Each IR Region Has a Specific Value in Spectroscopy

  • Near‑Infrared (NIR) Spectroscopy measures overtone and combination bands of fundamental vibrations. These transitions are typically weak so that measurements that require non-destructive deep energy penetration are addressed by NIR. Examples include quantitative bulk analysis, moisture and protein determination, and various process analytics.

  • Mid‑Infrared (MIR) Spectroscopy measures fundamental vibrational modes of most functional groups. Mid‑IR bands directly reflect bond strengths, molecular symmetry, and chemical environment. This region is typically addressed by FTIR spectroscopy, enabling functional‑group identification, reaction monitoring, polymer characterization, crystallinity assessment, and mechanistic studies. 

  • Far‑Infrared (FIR) Spectroscopy measures low‑energy vibrational and rotational modes, such as lattice phonons, metal–ligand vibrations, and hydrogen‑bond networks. Far‑IR is useful for inorganic and coordination chemistry, crystal‑field analysis, polymorph differentiation, and phonon studies in a range of engineered materials. 

Key Industrial Application Examples: Pharmaceuticals, Chemicals, and Polymers

Pharmaceuticals

Case Study: Crystallization Process Design for Monoclonal Antibodies

Research from MSD Werthenstein BioPharma and Merck & Co. demonstrated how in-situ analytical technologies can support the development of robust crystallization processes for monoclonal antibodies (mAbs). Using a caffeine cocrystal of pembrolizumab as a model system, researchers evaluated batch and semicontinuous crystallization strategies to address challenges associated with mAb crystallization, including large molecular size, structural flexibility, and crystal instability during downstream processing.

In-situ ReactIR FTIR spectroscopy, calibrated against UPLC measurements, was used to monitor solute concentrations and track supersaturation depletion in real time, providing valuable insight into crystallization kinetics. Complementary ParticleTrack™ FBRM measurements enabled online detection of nucleation events and estimation of induction times, while microscopy was used to characterize particle size and morphology offline.

The study found that seeded crystallization significantly improved process reproducibility, reduced cycle times, and generated more uniform particle properties compared with unseeded crystallization. Semicontinuous seeded processes provided enhanced supersaturation control, resulting in improved particle size distribution and filterability. The integration of real-time FTIR and particle monitoring technologies enabled a deeper understanding of crystallization mechanisms and supported the development of scalable, data-driven manufacturing processes for crystalline mAb formulations.

“This study demonstrates that pembrolizumab caffeine cocrystal-1 can be consistently generated at laboratory scale in a reactor equipped with an overhead stirrer. Unseeded isothermal batch crystallizations showed that crystal form can be successfully controlled over a wide range of concentrations of PEG and DSS. Within these ranges, operating conditions were identified that enable obtaining a satisfactory product recovery within a cycle time that is deemed commercially viable. However, the reproducibility of unseeded experiments is poor and may result in batch-to-batch variability, which may be mitigated by the implementation of a seeding step.”

Codan, L., Larpent, P., Kalapos-Dobszay, R., Medrán, B., Reichert, P., Sirota, E., & Cote, A. (2026). Controlling the Size and Shape of Monoclonal Antibody Particles through Crystallization Process Design. Molecular Pharmaceutics, 23(6), 3383-3396.
https://doi.org/10.1021/acs.molpharmaceut.6c00046

Chemicals

Case Study: Mechanistic Insights for Sustainable Cyclododecanone Oxime Production

Researchers at SINOPEC Research Institute of Petroleum Processing developed a greener route to cyclododecanone oxime (CDOX), an important precursor for nylon-12 production. The study investigated the indirect transoximation of cyclododecanone using cyclohexanone oxime over acidic zeolite catalysts as a more sustainable alternative to conventional hydroxylamine-based oximation processes.

ReactIR™in-situ FTIR spectroscopy played a key role in elucidating the reaction mechanism and identifying conditions that maximize conversion and catalyst performance. Real-time spectral measurements revealed that solvent selection strongly influences the reaction pathway. In ethanol-water mixtures, ReactIR detected the rapid formation of hydroxylamine intermediates, providing direct evidence for an acid-catalyzed hydrolysis pathway that facilitates oxime transfer and promotes higher reaction rates. In contrast, hydroxylamine was not observed in anhydrous ethanol, confirming that the reaction proceeds through an alternative, less efficient transoximation mechanism.

By providing continuous insight into intermediate formation and reaction progression, ReactIR enabled researchers to correlate catalyst activity with solvent effects and mechanistic pathways. The study demonstrated that the HBeta-21 zeolite catalyst, combined with an ethanol-water solvent system, offers an efficient and environmentally friendly route to CDOX production while highlighting the value of in-situ FTIR for reaction mechanism investigation, catalyst development, and process optimization.

“The indirect transoximation reaction catalyzed by zeolite is an effective and green approach to synthesize CDOX. The results indicated that HBeta-21 zeolite promoted a CDON conversion of 64.41% in the ethanol-H2O system, which was higher than that of 44.52% in ethanol…The reaction pathway in the ethanol-H₂O system was elucidated through in-situ FTIR spectroscopy (React IR™) and isotope-labeling experiments. In the ethanol-H2O system, the hydrolysis of CHO is rate-determining step, and NH2OH was produced as an intermediate with the low activation barrier (7.73 kJ/mol). In ethanol, the reaction rate depends equally on the concentrations of both reactants, and CHO+ was produced as an intermediate with the high activation barrier (18.44 kJ/mol).”

Li, M., Wang, Y., Luo, Y., & Shu, X. (2026). An efficient and green approach for synthesis of dodecanone oxime from the zeolite-catalyzed indirect transoximation reaction. Chemical Engineering Journal Green and Sustainable, 2, 100070.
https://doi.org/10.1016/j.cejgas.2026.100070

Polymers

Case Study: PET Depolymerization and Chemical Recycling

Researchers at the National Institute of Advanced Industrial Science and Technology (AIST) developed a scalable PET depolymerization process and a novel in-situ FTIR monitoring approach to evaluate chemical recycling performance in real time. The work focused on PET methanolysis, a recycling pathway that converts polyethylene terephthalate (PET) into dimethyl terephthalate (DMT), a purified monomer suitable for reuse in polymer production.

To improve process efficiency, the researchers developed a potassium carbonate (K₂CO₃)-catalyzed system that achieved effective PET depolymerization while maintaining low reaction pressure and favorable green chemistry metrics. K₂CO₃ generates potassium methoxide in situ, which catalyzes the cleavage of PET ester bonds and promotes monomer recovery under relatively mild conditions.

ReactIR in-situ FTIR spectroscopy was used to continuously monitor DMT formation throughout the reaction, enabling real-time determination of reaction kinetics, product yields, and time-resolved green chemistry metrics. Complementary EasySampler™ technology provided time-stamped samples for NMR validation and byproduct identification, while an EasyMax™ automated reactor ensured precise control of reaction conditions.

The integrated workflow enabled researchers to quantify reaction performance, identify active catalytic species, investigate catalyst deactivation mechanisms, and support process scale-up. The study demonstrated that in-situ FTIR can provide continuous process insight while enabling data-driven evaluation of sustainability, reaction efficiency, and scalability in chemical recycling applications.

“The developed in-situ FT-IR monitoring method enabled time-resolved evaluation of the energy economy factor (e), environmental factor (E), and environmental energy impact (x)… Kinetic analysis of in-situ FT-IR data using a reaction-controlled shrinking cylinder kinetic model enabled us to determine an apparent rate constant and the corresponding activation energy…These results demonstrate that the K₂CO₃-catalyzed DCAM of PET is readily scalable and that in-situ FT-IR serves as a powerful and practical tool for real-time monitoring of process scale-up.” 

Ogiwara, H., Yamamoto, T., Ogawa, A., Hiyoshi, N., Yoshida, M., & Tanaka, S. (2026). Time-resolved green Chemistry Metrics for low energy depolymerization of polyethylene terephthalate. ChemRxiv. https://doi.org/10.26434/chemrxiv.15005558/v1 

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Dr. Karsten Keller of Nitto Denko Avecia presents "PAT for the Future of Oligonucleotide Manufacturing".
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This webinar focuses on how to improve process development and scale-up by leveraging calorimetry and in situ process analysis. In order to provide t...
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FTIR In Peer-Reviewed Literature

Pharmaceuticals

  • Ji, Y., Mattern, K. A., Qin, Y., Badir, S. O., Grosser, S. T., Marzijarani, N. S., & Foley, D. A. (2026). Data-Rich monitoring and optimization of a complex biocatalytic oxidative desymmetrization via integrated Flow-NMR and PAT. Organic Process Research & Development, 30(3), 562–567. https://doi.org/10.1021/acs.oprd.5c00470
  • Akturk, I., Mackey, J. S., Sundarkumar, V., Murbach, G., Joglekar, G., Csathy, A. T., Wehrle, F. J., Thompson, D. H., & Nagy, Z. K. (2026). Toward agile, distributed pharmaceutical manufacturing: continuous End-to-End integration of reaction, purification, and formulation for Lomustine via the MiniPharm platform. Organic Process Research & Development, 30(3), 595–618. https://doi.org/10.1021/acs.oprd.5c00314
  • Wang, R., Xu, L., Yang, Y., Wang, W., Liu, M., Su, X., & Shao, Y. (2026). Real-Time Process Monitoring Ammonolysis of Oligonucleotides with Online FTIR Spectroscopy. Organic Process Research & Development, 30(3), 731–740. https://doi.org/10.1021/acs.oprd.5c00476
  • Arunachalampillai, A., Chandrappa, P., Crockett, R. D., Gaines, C. S., Hu, K., Judd, T., Kommuri, V. C., Murray, J. I., Nidhiry, J., Ortiz, A., Robinson, J. A., Rötheli, A. R., Vernon, R. M., Wei, C. S., Wells, S., Wilson, C. V., Xu, S., Yamamoto, K., & Zetzsche, L. E. (2025). Development of a Manufacturing Route toward AMG 193, an MTA-Cooperative PRMT5 Inhibitor. Organic Process Research & Development, 29(11), 2934–2941. https://doi.org/10.1021/acs.oprd.5c00310
  • Nagato, Y., Baba, Y., Shoji, M., Suzumura, Y., & Nakajima, N. (2025). Process development of the novel LPXC inhibitor T-1228. Part 3: Optimization of the deprotection reaction and the crystallization for the final step of API synthesis. Organic Process Research & Development, 29(12), 3049–3062. https://doi.org/10.1021/acs.oprd.5c00167
  • Lima, F. a. R. D., De Moraes, M. G. F., Secchi, A. R., De Souza, M. B., & Grover, M. A. (2025). Experimental nonlinear model predictive control of crystal size and yield in batch cooling crystallization enabled by soft sensor and Symbolic-Based calibration model. Industrial & Engineering Chemistry Research, 64(49), 23582–23600. https://doi.org/10.1021/acs.iecr.5c03894
  • Talbot, F. J. T., Lindsay‑Scott, P. J., Stokes, S., Barnes, A., Rees, M., Miller, I., Richardson, J., & Tang, X. (2026). ReactIR monitoring of Turbo‑Hauser base formation enables a robust iodination reaction during an early scale‑up campaign. Organic Process Research & Development, 30(4), 1041–1049. https://doi.org/10.1021/acs.oprd.6c00062
  • Codan, L., Larpent, P., Kalapos-Dobszay, R., Medrán, B., Reichert, P., Sirota, E., & Cote, A. (2026). Controlling the size and shape of monoclonal antibody particles through crystallization process design. Molecular Pharmaceutics, 23(6), 3383–3396. https://doi.org/10.1021/acs.molpharmaceut.6c00046
  • Fang, Z., Nie, T., Lan, Y., Cai, Q., & Wang, X. (2026). Mechanism-inspired chiral binuclear Cu catalysis for click chemistry: Highly efficient kinetic resolution to α‑quaternary amino acid derivatives. Journal of the American Chemical Society, 148(27), 29326–29335. https://doi.org/10.1021/jacs.6c08637
  • Anjali, & Upadhyay, S. (2026). Catalyst-free synthesis of triazoloquinoline derivatives via HOSA-mediated nitrile intermediates: Mechanistic insight, substrate scope, and in vitro biological evaluation. Main Group Chemistry. https://doi.org/10.1177/10241221261465085
  • Vasanth, S., Navyatha, J., Senthilkumar, T., Sowntharya, P., & Dhayalan, V. (2026). Organometallic Reagent‐Mediated functionalization of aromatic compounds in Continuous‐Flow system. Chemical Engineering & Technology, 49(7). https://doi.org/10.1002/ceat.70273
  • Shen, H., Sandvoß, A., Hughes, W. B., Tyler, J. L., McPherson, L. J. M., Coles, S. J., Paton, R. S., & Aggarwal, V. K. (2026). Electrophilic amination-induced 1,2-boronate migration for the modular synthesis of β-amino boronic esters. Nature Chemistry. https://doi.org/10.1038/s41557-026-02206-6

Chemicals

  • Li, D., Mao, Q., Xiong, C., Xi, L., Nie, Y., Xu, X., & Ji, H. (2026). Constructing Ru‑porphyrin COF for catalyzing air oxidation of adamantane C–H bonds to relay olefin epoxidation. Chinese Journal of Catalysis, 88, 442–456. https://doi.org/10.1016/S1872-2067(26)65132-7 
  • Geng, J., Zhang, H., Wei, Q., Fu, H., Gao, H., & Liao, Y. (2026). Enhancing nitrogen fixation via electron transfer between Bi₂MoO₆ and BiOCl heterojunction photocatalysts. New Journal of Chemistry. https://doi.org/10.1039/d6nj02173e
  • Nishino, S., Inamura, K., & Kurahashi, T. (2026). Substrate‑paired electron donor–acceptor complexes enable photochemical alkyl–alkyl cross‑coupling. Organic Letters. https://doi.org/10.1021/acs.orglett.6c02921
  • Maxwell, V., Karagiannis, A., Schramm, T. K., Kotelnikow, V., Gupta, R., Lalancette, R. A., Appel, A. M., Hansen, A., Wiedner, E. S., & Prokopchuk, D. E. (2026). Steric Mapping, Ligand Dynamics, and Cycloisomerization Catalysis with Redox Robust Mn I/0/-I Dicarbenes. Organometallics, 45(12), 1355–1367. https://doi.org/10.1021/acs.organomet.6c00057
  • Li, M., Wang, Y., Luo, Y., & Shu, X. (2026). An efficient and green approach for synthesis of dodecanone oxime from the zeolite-catalyzed indirect transoximation reaction. Chemical Engineering Journal Green and Sustainable, 2, 100070. https://doi.org/10.1016/j.cejgas.2026.100070
  • Abdoun, S., Bour, C., Mayer, R. J., & Vayer, M. (2026). Electrochemical N -Propargylation of N -Heterocycles via decarboxylation of allenoic acids. ACS Organic & Inorganic Au, 6(3), 314–324. https://doi.org/10.1021/acsorginorgau.5c00117
  • Zars, E., Beagan, D., Reed, S., Zeller, M., Lehnert, N., & Szymczak, N. (2026). N-N coupling of nitrosyl ligands in a dinitrosyl iron complex mediated by exogenous acids. ChemRxiv. https://doi.org/10.26434/chemrxiv-2025-9z9lk/v2
  • Zhang, C., Ma, Y., Wang, Z., Jia, S., Zhang, Y., Yang, L., Yang, H., Cheng, J., & Yang, C. (2026). Influence of seed properties and operating conditions on secondary nucleation of glyphosate. Industrial & Engineering Chemistry Research, 65(15), 7826–7839. https://doi.org/10.1021/acs.iecr.5c04870
  • Sagmeister, P., Matsunami, K., Aprile, G., Whitaker, D. A., Janoudi, M., Toupy, T., Galilea, A. R., Nazemifard, N., Papageorgiou, C. D., Bhaskar, A., Mack, J., Braatz, R. D., & Myerson, A. S. (2026). Hydrogenation Process development in a Data-Rich environment. Organic Process Research & Development, 30(7), 2008–2018. https://doi.org/10.1021/acs.oprd.6c00149
  • Botlik, B. B., Vieira, A. N., Mitschke, B., Ruepp, F., & Morandi, B. (2026). C═C/N═O metathesis enables oxidative decarboxylation. Journal of the American Chemical Society, 148(26), 27782–27791. https://doi.org/10.1021/jacs.6c08509
  • Ghaffari, S., Gänsch, J., Schulze, P., & Lorenz, H. (2026). Crystal growth kinetics of NA 2 CO 3 hydrate phases in the NA 2 CO 3 –NAOH–H 2 O system for sustainable soda ash production. ACS Omega, 11(5), 7741–7755. https://doi.org/10.1021/acsomega.5c09440
  • Crouse, S. H., Rousseau, R. W., & Grover, M. A. (2026). Real‐time fault detection in multicomponent nuclear‐waste slurries through data fusion of spectroscopic sensors. AIChE Journal, 72(5). https://doi.org/10.1002/aic.70234
  • Lorraine, S. C., Baur, A., Taylor, N., Dolinar, B. S., & Hoover, J. M. (2026). Field effects Govern the decarboxylation of Copper(II)-Benzoates: Kinetic and Mechanistic studies. Organometallics, 45(2), 169–180. https://doi.org/10.1021/acs.organomet.5c00415
  • Lima, F. a. R. D., Abdelrehim, A., Bharambe, A., Micluța-Câmpeanu, M., Gandhi, D., Bhat, V., Singhvi, A., Piibeleht, M., Secchi, A., De Souza, M. B., Leblebici, M. E., Rackauckas, C., & Nogueira, I. (2026). Assessment of the DYAD Agentic Modeling Language in Process Systems Engineering. Research Square. https://doi.org/10.21203/rs.3.rs-8475139/v1

Polymers

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  • Zou, X., Xie, T., Xu, J., Bai, H., Wang, D., Ke, X., Zhao, W., & Lv, M. (2026). Unveiling Autocatalytic Kinetics in the Short-Chain Polyaddition of Poly(amic acid) by In Situ FTIR. Industrial & Engineering Chemistry Research, 65(10), 5452–5459. https://doi.org/10.1021/acs.iecr.6c00046
  • Duan, W., Zhao, S., Wen, Y., Duan, Z., Zhang, L., & Liu, B. (2026). Dilution-Tolerant organoboron catalyst for the copolymerization of CO 2 and propylene oxide enabled by a cyclic anhydride. Macromolecules, 59(4), 2040–2051. https://doi.org/10.1021/acs.macromol.5c03427
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  • Yang, Y., Guan, Z., Wang, R., Wang, W., Zhang, M., Su, X., & Shao, Y. (2026). Optimization of the Solid-Phase oligonucleotide detritylation reaction using In-Line IR spectroscopy. Organic Process Research & Development, 30(5), 1369–1377. https://doi.org/10.1021/acs.oprd.6c00103
  • Ogiwara, H., Yamamoto, T., Ogawa, A., Hiyoshi, N., Yoshida, M., & Tanaka, S. (2026). Time-resolved green Chemistry Metrics for low energy depolymerization of polyethylene terephthalate. ChemRxiv. https://doi.org/10.26434/chemrxiv.15005558/v1

What is the difference between IR and FTIR?

Traditional IR spectroscopy is dispersive, measuring one wavelength at a time, whereas FTIR (Fourier Transform Infrared) measures all frequencies simultaneously using an interferometer. This results in significantly faster data collection, higher resolution, and a much better signal-to-noise ratio. 

What does an FTIR spectrum tell you?

An FTIR spectrum acts as a molecular fingerprint, showing peaks that correspond to specific chemical bond vibrations (stretching, bending) at characteristic wavenumbers. It allows researchers to identify functional groups, determine chemical structures, and quantify components within a mixture. 

Why is FTIR used for in-situ reaction monitoring?

FTIR is ideal for in-situ reaction monitoring because it provides real-time data on reactant consumption, intermediate formation, and product generation as chemistry progresses. Using probe-based FTIR technology, scientists can track reaction kinetics, reaction mechanisms, and endpoint determination under actual process conditions without disturbing the sample.

What are the main advantages of FTIR over dispersive IR spectroscopy?

FTIR offers three primary advantages: the Felgett (multiplex) advantage, where all frequencies are measured simultaneously for faster results; the Jacquinot (throughput) advantage, which allows more energy to reach the detector for higher sensitivity; and the Connes (frequency precision) advantage, utilizing internal laser calibration for high wavelength accuracy.

What is ATR-FTIR and when should it be used? 

Attenuated Total Reflectance (ATR) is a sampling technique where IR light reflects off the internal surface of a high-refractive-index crystal in contact with the sample. It is ideal for analyzing solids, liquids, and pastes without extensive sample preparation, making it the standard for rapid material identification.

Can FTIR be used for quantitative analysis? 

Yes, FTIR is highly effective for quantitative analysis by applying the Beer-Lambert Law. By measuring the absorbance intensity of specific functional group peaks, scientists can determine the concentration of components in a mixture with high precision. 

What are the some core applications of FTIR?

FTIR in the Pharmaceutical Sector

Quality Control and Assurance (offline)

  • Raw material identity testing and verification
  • Blend uniformity checks
  • Confirmation of final‑product composition
  • Cleaning validation
  • Polymorph screening
  • API–excipient interaction assessment
  • Degradation studies

Process R&D / Manufacturing (online)

  • Track reagent depletion, intermediate formation, protecting‑group removal, and impurity pathways
  • Follow and verify reaction progress and end‑point determination
  • Determine reaction kinetics and mechanisms
  • Support DoE and optimization studies
  • Monitor chemistry in batch or flow systems
  • Support crystallization R&D via crystal‑morphology transitions and supersaturation monitoring
  • Enable automated optimization workflows
  • Provide PAT‑based control in continuous manufacturing processes

FTIR in Chemical R&D / Manufacturing

Quality Assurance / Quality Control (offline)

  • Validate feedstock purity
  • Confirm product identity
  • Troubleshoot off‑spec batches
  • Support in‑process control

R&D / Manufacturing (online)

  • Monitor key reactions directly in reactors (acid–base neutralizations, polymerizations, oxidations, reductions, catalytic transformations)
  • Enable early detection of runaway conditions, impurity formation, or catalyst deactivation
  • Provide live concentration profiles for automated feedback control in flow processes, ensuring steady state and consistent product quality
  • Support energetic‑material (explosives, propellants) development and safety studies

FTIR in Polymer Chemistry

Quality Assurance / Quality Control (offline)

  • Structural identification and polymer‑type verification
  • Additive and formulation analysis
  • Curing and crosslinking assessment
  • Degradation and failure analysis
  • Surface and coating characterization
  • Blend and copolymer analysis

Polymer R&D / Manufacturing (online)

  • Track monomer conversion, functional‑group consumption, crosslinking, and degradation
  • Monitor free‑radical polymerizations: quantify conversion curves, induction periods, and rate changes driven by initiator concentration, temperature, or inhibitors
  • Monitor step‑growth systems (polyesters, polyamides, polyurethanes): track carbonyl, hydroxyl, amine, and isocyanate bands for stoichiometric control and early detection of side reactions
  • Track epoxy and silicone curing via epoxy ring opening or Si–H consumption to assess crosslink density, gelation behavior, and cure endpoints
  • Biopolymer synthesis - monitor deprotection, coupling, and linkage‑formation steps in SPPS and SPOS.
  • Support reactive extrusion, reactive blending, and flow‑polymerization platforms
  • Conduct degradation studies: detect oxidation, hydrolysis, and chain‑scission signatures
  • Support chemical/molecular recycling, closed‑loop recycling, valorization, and circular‑economy efforts
Professional headshot of Dr. Alan Rein, Technical Marketing Consultant

Dr. Alan Rein, Ph.D.

Technical Marketing Programs Consultant

For six decades, Dr. Rein has been involved in the development, application and/or marketing of scientific instrumentation in the chemical, pharmaceutical, defense, and aerospace industries. His focus has been in the use of FTIR and Raman spectroscopy in real-time measurements and out-of-lab applications. His early collaborations with METTLER TOLEDO personnel and customers led to the eventual formation of the AutoChem group.

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