Mid-Infrared MIR Spectroscopy

In the MIR spectral region we are dealing with transitions between various vibrational energy levels of molecules. Gaseous samples are a special case, because rotational fine-splitting of spectral bands can be observed. Fine-splitting is caused by simultaneous excitation of rotational and vibrational transitions. 

The MIR spectral range extends from 4000 to 400 cm . Transitions can be observed by absorption or emission measurements. For analytical purposes, absorption measurements are usually preferred. The decision about an optimal sampling technique is very much dependent on the aggregate state of the sample under investigation. 

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Mid-infrared (MIR) spectroscopy MIR spectroscopy (frequency range 2.5-25nm or 4000 00 cm ) is a popular technique for identification assays (chemical identity) of dmg substances in pharmacopoeias. The fact that different solid-state forms exhibit different MIR spectra represents rather a problem for such purposes. Thus, in the case that the spectmm of a compound, whose identity needs to be determined or confirmed, is different than that of the reference compound, pharmacopoeias suggest either to record the spectra in solution or to recrystallize both the substance and the reference using the same method before recording their solid-state spectra. 

A more advanced sorting is achieved by use of mid-infrared (MIR) and near-infrared (NIR) spectroscopy. These methods are used at several sites, but suffer from insensitivity when the mixed plastics are dirty and/or painted or have a paper label. In addition, for NIR, it is not possible to separate dark plastics [19, 20]... 

In sim infrared (IR) spectroscopy is a spectroscopic method for the infrared spectral range which can be used in defined environments during preparation, modification, function, and reaction or analysis in natural environment. In this contribution especially liquid environments are considered with the focus on the mid-infrared (MIR) spectral range from 2.5 to 16 pm. 

Depending on the type of reaction and analytes to be investigated, different optical spectroscopic methods are available [7]. Typically UV-Vis, near-infrared (NIR), mid-infrared (MIR) and Raman spectroscopy are the most popular in process analysis (see Table 6.1) [8]. Other, emerging in-line methods such as fluorescence and chemiluminescence spectroscopy are still of minor importance in process technologies and will be not discussed here (for additional information, see [9]). 

Two-dimensional correlation spectroscopy is used for detailed band assignment work. The technique allows spectral information to be analyzed that is much richer in information content than one-dimensional data. Cross-correlation analysis methods are applied to spectral combinations of NIR with NIR, or NIR and mid-infrared, allowing band assignments to be more easily accomplished. An excellent review paper describing the mathematics used in 2-D correlation spectroscopy along with several examples of generalized 2-D NIR and 2-D NIR-mid-infrared (MIR) heterospectral correlation analysis are introduced with 42 references by Ozaki and Wang. °... 

As instrumentation has become available, Raman spectroscopy has started to gain acceptance in both the quality assurance/quality control (QA/QC) and process control fields. In Table 1, a comparative summary of Raman spectroscopy and mid-infrared (MIR) and near-infrared (NIR) spectroscopies is presented. 

Chromatographic and spectroscopic techniques are within the most important tools used in food autherrtication. In particular, gas chromatography (GC) and liquid chromatography (LC) are widely used for the determination of both polar and non-polar compormds (volatile compormds in the case of GLC and organic acids, amino acids, polyphenols, etc., for LC). Almost aU the irrfrared spectroscopic techniques, near infrared (NIR) spectroscopy and mid-irtfrared (MIR) spectroscopy, are cheap, rapid, and non-destructive. AU of them are frequently used in combination with chemometrics. 

Modern infrared (IR) spectroscopy is a versatile tool applied to the qualitative and quantitative determination of molecular species of all types. Its applications fall into three categories based on the spectral regions considered. Mid-IR (MIR) is by far the most widely used, with absorption, reflection, and emission spectra being employed for both qualitative and quantitative analysis. The NIR region is particularly used for routine quantitative determinations in complex samples, which is of interest in agriculture, food and feed, and, more recently, pharmaceutical industries. Determinations are usually based on diffuse reflectance measurements of untreated solid or liquid samples or, in some cases, on transmittance studies. Far-IR (FIR) is used primarily for absorption measurements of inorganic and metal-organic samples. 

In this context, we used Fourier Transform Infrared-Mid Infrared-Attenuated Total Reflectance (FT-MIR-ATR) spectroscopy to characterize nine of the most important hydrophilic polymers used for microencapsulation, easy to form gels, namely, alginate, K-carrageenan, chitosan,... 

The method of infrared (IR) spectroscopy, discovered in 1835 has so far produced a wealth of information on the architecture of matter in our planet and even in the far away stars. Infrared spectroscopy is a powerful technique that allows us to learn more about the structure of materials and their identification and characterization. This study is based on the interaction of electromagnetic (EM) radiation with matter. The EM radiation has energy states comparable to the vibrational energy states of the molecules. These states are included in the energy region between 14000 cm and 100 cm i of the Electromagnetic Radiation, which is divided in three sub-regions called 1) NEAR-IR, o r NIRS 2) MID-IR or MIRS and 3) FAR-IR. or EIRS ... 

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