FTIR Spectroscopy FAQs
What is FTIR Spectroscopy?
FTIR spectroscopy (FTIR) is an analytical methodology that is widely used in industry and academic laboratories to understand the structure of individual molecules and the composition of molecular mixtures. FTIR spectroscopy uses modulated, mid-infrared energy to interrogate a sample. The infrared light is absorbed at specific frequencies related to the vibrational bond energies of the functional groups present in the molecule. A characteristic pattern of bands is formed, which is the vibrational spectrum of the molecule. The position and intensity of these spectral bands provide a fingerprint of molecular structure, making FTIR spectroscopy a highly adaptable and useful technique. FTIR spectroscopy is a great advance over the traditional dispersive infrared approach for a number of reasons including that the entire FTIR spectrum is collected in a fraction of a second and, by co-adding spectra, signal to-noise is improved.
What is FTIR Spectroscopy used for?
FTIR spectroscopy has broad use and applicability in the analysis of molecules important in the pharmaceutical, chemical and polymer industries. FTIR spectroscopy is widely used in industry and academic laboratories to better understand reaction kinetics, mechanism and pathways as well as catalytic cycles. In qa/qc labs, FTIR spectroscopy is used to ensure that raw materials, intermediate compounds and final products meet content and purity specifications. In chemical product development, FTIR spectroscopy is used to help scale-up chemical reactions, optimize reaction yield and minimize impurities. In chemical production, FTIR spectroscopy helps to ensure that processes are stable, in control, and meet end-product specifications and impurity profiles.
How Does FTIR Spectroscopy Work?
The classic Fourier transform infrared spectrometer consists of several key components – a light source, typically an infrared radiator, an interferometer such as a Michaelson with both fixed and moving mirror, a sample compartment, and a thermal or photonic detector. Broad band infrared energy from the source is directed onto a beamsplitter, which passes the energy along two different paths. One path has a fixed mirror at the end; the other a moving mirror. The infrared energy from these two paths return and recombine at the beamsplitter causing a constructive and destructive interference pattern, the interferogram. This modulated infrared beam is passed to the sample where it is absorbed as a function of the molecular structure of the sample. The resultant interferogram is treated with a Fourier transform that converts the intensity vs. time signal into the intensity vs. frequency spectrum. The single beam sample spectrum is ratioed against a reference spectrum to remove the background contributions, resulting in the typical infrared absorbance/transmission spectrum
Why Use FTIR Spectroscopy?
In many instances, reaction understanding requires the construction of accurate reaction profiles for each species that are expressed as concentration versus time, leading to the determination of reaction kinetics. FTIR Spectroscopy is an ideal technique to provide this information, as it allows the rapid collection of detailed reaction profiles.
What advantages does FTIR Spectroscopy bring to reaction analysis?
FTIR Spectroscopy brings a couple of advantages to reaction analysis. First, the use of the fingerprint region of the mid-infrared enables the individual tracking of chemical species, which in turn provides clues to the mechanism of the reaction. Second, Beer's Law gives the connection between the measured absorbance of the reaction species and its concentration. This relationship means we can use an offline measurement to determine the concentration of an offline sample, and then use that data point to scale the mid-infrared profile. There is a correlation between the concentration measurement of offline samples and the measured shape of the in situ samples.
Why use FTIR Spectroscopy instead of alternative techniques?
Mid-infrared attenuated total reflectance (ATR) technology offers numerous advantages over alternative analytical methods, including other molecular spectroscopy techniques. Researchers and scientists improve chemical development by leveraging these advantages, including:
- Immersible for direct insertion into reaction vessel for in situ, continuous, real-time measurements
- No extractive sampling required, providing the ability to measure chemistry in its natural environment
- Impervious to bubbles or solids, making it ideal for hydrogenations or any heterogeneous reactions
- Suitable for aqueous chemistry
- Non-destructive, preserving the integrity of the chemical reaction
- Adheres to Beer-Lambert law, enabling both qualitative and quantitative measurements
Instantaneous information can be gained about a reaction from FTIR spectroscopy because it is an in situ technique. This is a key benefit to obtaining further insights into reaction behavior, particularly where transient species are involved.
Why is the data generated from FTIR Spectroscopy so important?
The reason why the data is so important is because of its continuous nature. With FTIR Spectroscopy, data collection is automated, typically generating concentration information every minute, even as fast as four times every second. This means that rather than running a large number of reactions to understand rate dependencies, just a few experiments can provide the necessary information to determine the driving forces of a reaction supporting reaction mechanistic theory. This means that research can progress at an accelerated rate. In addition, the data is often more accurate than data analyzed by offline techniques as there is no possible alteration of the molecules by preparation for analysis, or by exposing it to an enviroment other than that within the reaction vessel.
What industries use FTIR Spectroscopy?
FTIR Spectroscopy is used in the pharmaceutical, chemical, and petrochemical industries as well as in academic research.
What is FTIR Spectroscopy used for in the Pharmaceutical Industry?
- Organic Synthesis
- Grignard Reactions
- Hydrogenation Reactions
- Asymmetric Catalysis
- Enzymatic Catalysis
- Cross Coupling Reactions
- Organometallic Chemistry
- Solution Phase and Heterogeneous Catalysis
What is FTIR Spectroscopy used for in the Chemical industry?
- Flavors and Fragrances
- Bulk Chemicals
- Isocyanate Chemistry
- Highly Oxidizing Reactions
- Catalytic Processes
What is FTIR Spectroscopy used for in Academic Research?
- Metal-Mediated Chemistry
- C-H Activation
- Mechanistic Studies
- Reaction Kinetics