FT-IR spectrometer Q&A
Q1: What is laser class of FT-IR spectrometer?
A1: FT-IR spectrometer uses laser class Ⅰ according to FDA standard.
What is FTIR spectrometers ?
FTIR stands for Fourier Transform Infrared Spectrometer, which are widely used in organic synthesis, polymer science, petrochemical engineering, pharmaceutical industry and food analysis.
What is FTIR spectrometer range?
The range of Infrared region is 12800 ~ 10 cm-1 and can be divided into near-infrared region (12800 ~ 4000 cm-1), mid-infrared region (4000 ~ 200 cm-1) and far-infrared region (50 ~ 1000 cm-1).
How is the FTIR spectrometer discovered?
The discovery of infrared light can be dated back to the 19th century. Since then, scientists have established various ways to utilize infrared light. Infrared absorption spectroscopy is the method which scientists use to determine the structures of molecules with the molecules’ characteristic absorption of infrared radiation. Infrared spectrum is molecular vibrational spectrum. When exposed to infrared radiation, sample molecules selectively absorb radiation of specific wavelengths which causes the change of dipole moment of sample molecules. Consequently, the vibrational energy levels of sample molecules transfer from ground state to excited state. The frequency of the absorption peak is determined by the vibrational energy gap. The number of absorption peaks is related to the number of vibrational freedom of the molecule. The intensity of absorption peaks is related to the change of dipole moment and the possibility of the transition of energy levels. Therefore, by analyzing the infrared spectrum, one can readily obtain abundant structure information of a molecule. Most molecules are infrared active except for several homonuclear diatomic molecules such as O2, N2 and Cl2 due to the zero dipole change in the vibration and rotation of these molecules. What makes infrared absorption spectroscopy even more useful is the fact that it is capable to analyze all gas, liquid and solid samples. The common used region for infrared absorption spectroscopy is 4000 ~ 400 cm-1 because the absorption radiation of most organic compounds and inorganic ions is within this region.
What is advantage of FTIR spectrometers?
The signal-to-noise ratio of spectrum is significantly higher than the previous generation infrared spectrometers.
The accuracy of wavenumber is high. The error is within the range of ± 0.01 cm-1.
The scan time of all frequencies is short (approximately 1 s).
The resolution is extremely high (0.1 ~ 0.005 cm-1).
The scan range is wide (1000 ~ 10 cm-1).
What are Components of FTIR Spectrometers?
FTIR spectrometer consists of a source, interferometer, sample compartment, detector, amplifier, A/D convertor, and a computer. The source generates radiation which passes the sample through the interferometer and reaches the detector. Then the signal is amplified and converted to digital signal by the amplifier and analog-to-digital converter, respectively. Eventually, the signal is transferred to a computer in which Fourier transform is carried out. 
What is IR spectroscopy?
Infrared (IR) light is found in the part of the electromagnetic spectrum that sits right at the low-energy side of visible light.
The electromagnetic spectrum, with a focus on the infrared section.
When IR light interacts with a molecule, it can potentially initiate vibrations in the sample. The individual bonds in a molecule have different characteristic vibrations depending on, for example, the bond strength and the attached atomic masses. If the energy of the IR light matches the energy required to start one of the molecular vibrations, then the IR light is absorbed.
Infrared (IR) light can initiate molecular vibrations. The required energy depends on, for example, the bonds strength and the attached masses.
IR spectroscopy is a technique that uses an IR spectrometer to measure the light energy required to start molecular vibrations in a sample. Each functional group in a molecule has characteristic unique vibrations that are reflected at different bands in the IR spectrum. Therefore, individual bands in an IR spectrum can be used to determine what functional groups are present in a sample. The bands of all these different functional groups together result in a Fourier transform infrared (FTIR) spectrum that can be considered a fingerprint of the sample. The region in which most of the characteristic vibrations are present is called the fingerprint region. The fingerprint region is located at the lower end of the so-called mid-IR region.
Bands of different functional groups together result in an infrared (IR) spectrum that can be considered a fingerprint of the sample.
Most uses of IR spectroscopy require light from the mid-IR region, which spans from about 4000 to 400 cm-1.
How does an FTIR spectrometer work?
All Fourier transform infrared (FTIR) spectrometers require three basic components:
An IR light source that emits the IR light
An interferometer that time-dependently modifies the spectral composition of the IR light
A detector that detects the light intensity
When the IR light enters the interferometer, a beam splitter divides the light into two optical beams. The first beam is reflected by a fixed mirror, while the second beam is reflected by a moving mirror. This mirror constantly moves back and forth and, depending on its position, the second beam travels a longer or shorter distance. The two beams meet again at the beamsplitter, where they interfere with each other. Due to the changing traveling distance of the second beam, the resulting IR light exiting the interferometer has a constantly changing frequency distribution. The detector records this “interferogram”—a function of the signal intensity versus time (= mirror position) —which is Fourier transformed by a computer into a frequency spectrum—a function of the signal intensity versus frequency/wavenumber.
What is FTIR spectrometer qualitative or quantitative?
One of the great advantages of Fourier transform infrared (FTIR) spectroscopy is that it provides both qualitative and quantitative information from the same measured FTIR spectrum.
 FTIR spectroscopy is a very robust and reliable technique for the positive identification of unknown samples. The collected IR spectrum of an unknown sample is compared to a great number of IR spectra of known compounds. Each compound features a rather unique IR spectrum, and if the measured IR spectrum of an unknown sample matches one of the known spectra, it is fair to say that these compounds are identical.
Comparing the Fourier transform infrared (FTIR) spectrum of an unknown sample with spectra of known compounds allows identification of the unknown.
It is also possible to extract quantitative information from an IR spectrum. This could be, for example, the position of a certain IR band. However, in most cases, it is used to determine the concentration of a substance in a sample. The IR spectra of standard samples with known concentration can be used to create a correlation curve. This correlation curve is then used to determine the concentration of the unknown sample from its IR spectrum. These “quantification models” can be based on signal intensity, band area, or for more challenging correlations chemometric approaches are also used.  
Once we have the calibration curve established, the infrared (IR) signal of an unknown sample can be used to determine the concentration of this unknown sample.
What is FTIR Analysis Techniques?
There are several FTIR analysis sampling techniques that can be used to understand a material’s structure and identify the material, each with their own proficiency:
Attenuated Total Reflectance – ATR spectroscopy only requires the sample come into contact with the ATR crystal.
Specular Reflectance – SR typically occurs with glossy samples, such as glass and crystal.
Reflection-Absorption – RA works with thin samples such as residues and paints
Transmission – TR passes IR (radiation) through gas, liquid or solid samples and measures how well the sample absorbs that infrared radiation.
Photoacoustic – PAS can be difficult, but not impossible. Infrared absorptions are converted to heat inside the sample, creating the photoacoustic signal.