MIR spectroscopy

Daniel-Kelly, J. F., Downey, G., and Fouratier, V. (2004). Initial study of honey adulteration by sugar solutions using midinfrared (MIR) spectroscopy and chemometrics. /. Agric. Food Chem. 52, 33-39. 

In Section 4.5.3, discussion was restricted to the application of BTEM to organome-tallic and homogeneous catalytic systems using MIR spectroscopy. However, it should also be noted that BTEM has been successfully applied to other problems in the chemical sciences using FTIR [104], RAMAN, FTIR and RAMAN [105, 106], as well as MS [107, 108]. A one-to-one comparison between BTEM and SIMPLISMA, OPA-ALS, has appeared [109]. 

To perform chemical imaging of sample surfaces, FT spectrometers can be coupled with a microscope or macrochamber with an FPA detector. CIS are available for Raman, NIR, and MIR spectroscopy. Figure 15 illustrates an optical arrangement for chemical imaging. 

J. M. Andrade, M. S. Sanchez and L. A. Sarabia, Applicability of high-absorbance MIR spectroscopy in industrial quality control of reformed gasolines, Chemom. Intell. Lab. Syst., 46, 1999, 41-55. 

New methods for non-destructive quantitative analysis of additives based on MIR spectra and multivariate calibration have been presented [67, 68], One of the limitations in the determination of additive levels by MIR spectroscopy is encountered in the detection limit of this technique, which is usually above the low concentration of additive present, due to their heavy dilution in the polymer matrix. The samples are thin polymer films with small variations in thickness (due to errors in sample preparation). The differences in thickness cause a shift in spectra and if not eliminated or reduced they may produce non-reliable results. Methods for spectral normalisation become necessary. These methods were reviewed and compared by Karstang et al. [68]. MIR is more specific than UV but the antioxidant content may be too low to give a suitable spectrum [69]. However, this difficulty can be overcome by using an additive-free polymer in the reference beam [67, 68, 69, 70]. On the other hand, UV and MIR have been successfully applied to quantify additives in polymer extracts [71, 72, 66]. 

We have studied the Jahn-Teller effect in this phase by MIR spectroscopy [31, 70]. The Ti (4) mode shows a twofold splitting and modes that are silent in Ceo appear, indicating a D3 or T>sd distortion of the molecule (Fig. 10). As the C o ions are rotating in this phase [73,74], the distortion cannot be caused by the crystal field but must be due to the molecular Jahn-Teller effect. As there is no crystal field to lock the Cgo into a single potential well, the distortion is dynamic, with the rate of pseudorotation smaller than that of the infrared measurement. 

GC/MS), liquid chromatography/mass spectrometiy (LC/MS/, and inductively coupled plasma mass spectrometry (ICP-MS) evolved to address TICs of various forms and characteristics. We present an all optical single sensing instrument, based on NIR and MIR spectroscopy, which can be used for the detection and concentration measurement of a large number of TICs in either liqnid or sohd phases. 

Photopolymerization of acrylic monomers and related systems is a challenging area for the application of real-time MIR spectroscopy since the reactions are often completed within seconds, so there needs to be an excellent SNR in the spectra if reliable kinetic data are to be generated. The temporal resolution of an FT-IR spectrometer at a resolution of 16 cm is 11 ms, so 100 spectra can be gathered in the time frame of the fastest reaction, but without multiplexing to improve the SNR. Using a diamond ATR element of area 4 mm that could also be heated to 200 C, uniform irradiation was possible and the cure reactions of films of thicknesses ranging from 1 to 20 pm could be followed (Scherzer and Decker, 1999). 

Scheme 3.1. Formation of oxidation products in the degradation of polypropylene through the tertiary hydroperoxide intermediate that may he identified by MIR spectroscopy (often combined with derivatization). After Blakey (2001).

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. 

These sanples demonstrate that MIR spectroscopy provides important structural information about solid-state forms, particularly where different hydrogen-bond associations are present as well as for hydrates and solvates. However, from our experience, MIR spectra of conformational polymorphs [29] with aliphatic chains are often barely distinguishable owing to rather weak interactions between the molecules. In order to identify or quantify such forms by spectrometry, Raman or solid-state NMR spectroscopy stands a better chance of success. 

There is a diversity of both natural and synthetic polymeric systems that have been analyzed and studied for the entrapment of bioactive molecules and their controlled release. The use of FT-MIR spectroscopy to characterize their specific fingerprint is a pre-requisite for an appropriate characterization of microcapsules. 

In conclusion, the most important advantages of FT-MIR spectroscopy to be used in biopolymer characterizations are the spectra can be obtained instantly in a solid form, liquid form, and in different solutions, the sample aliquots are small (less than 1 g), the operation of the equipment is simple, cheap, and the interpretation is done due to data processing software attached to instruments. No light scattering or fluorescent effects may interfere. "... 

Four comprehensive feasibility studies have been published, all of which differ in significant ways. Two were based upon MIR spectroscopy, and two on NIR spectroscopy. One MIR investigation used ATR spectroscopy, and another used dried serum films the two NIR studies differed in more subtle, yet substantial, details. 

ATR = MIR ATR spectroscopy of native serum i> Film MIR = MIR spectroscopy of dried serum films NIR A = NIR spectroscopy of native serum at 0.5-mm path length NIR B = NIR spectroscopy of native serum at 2.5-mm path length. ... 

In principle, serum or blood glucose may be quantified either by using MIR spectroscopy or by exploiting any of three sets of NIR absorptions, namely those corresponding to vibrational combination bands (2000-2500 nm), the first overtone absorptions (1400-1800 nm), or the second overtone bands (950-1250nm). All of these have been explored in attempting to quantitate serum glucose,... 

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