Infrared spectroscopy combination with other analytical

Infrared Spectroscopy (ir). Infrared curves are used to identify the chemical functionality of waxes. Petroleum waxes with only hydrocarbon functionality show slight differences based on crystallinity, while vegetable and insect waxes contain hydrocarbons, carboxyflc acids, alcohols, and esters. The ir curves are typically used in combination with other analytical methods such as dsc or gc/gpc to characterize waxes. 

Capillary electrophoresis has also been combined with other analytical methods like mass spectrometry, NMR, Raman, and infrared spectroscopy in order to combine the separation speed, high resolving power and minimum sample consumption of capillary electrophoresis with the selectivity and structural information provided by the other techniques [6]. 

In Chapter 6 we saw that, by itself, chromatography is not well suited to qualitative analysis thus it is often combined with other methods. The most successful combination has been GC with mass spectrometry (MS) GC s ability to separate materials and MS s ability to identify them has made the combination one of the most powerful analytical techniques available today. The other forms of chromatography are also being combined with MS and with infrared spectroscopy (IR). The resulting analytical methods are usually designated by their combined abbreviations (e.g., GC/MS or GC-MS) and are known as hyphenated techniques. The current status of these methods will be described briefly. 

Infrared spectroscopy has also been combined with other established analytical techniques, e.g. thermogravimetric analysis (TGA). The latter is a technique which involves measuring the change of the mass of a sample when it is heated. While TGA can provide quantitative information about a decomposition process, it is unable to identify the decomposition products. However, TGA and infrared spectroscopy have been combined to provide a complete qualitative and quantitative characterisation of various thermal decomposition processes. 

Perhaps the most revolutionary development has been the application of on-line mass spectroscopic detection for compositional analysis. Polymer composition can be inferred from column retention time or from viscometric and other indirect detection methods, but mass spectroscopy has reduced much of the ambiguity associated with that process. Quantitation of end groups and of co-polymer composition can now be accomplished directly through mass spectroscopy. Mass spectroscopy is particularly well suited as an on-line GPC technique, since common GPC solvents interfere with other on-line detectors, including UV-VIS absorbance, nuclear magnetic resonance and infrared spectroscopic detectors. By contrast, common GPC solvents are readily adaptable to mass spectroscopic interfaces. No detection technique offers a combination of universality of analyte detection, specificity of information, and ease of use comparable to that of mass spectroscopy. 

Infrared spectroscopy has been. combined with various other analytical techniques. Gas chromatography-infrared spectroscopy (GC-IR) allows the identification of the components eluting froiti a gas chromatograph. GC-IR has certain advantages over, say, gas chromatography-mass spectrometry (GC-MS). While GC-MS is able to distinguish easily between compounds of different mass, it is unable to differentiate structural isomers of the same molecular mass. By comparison, GC-IR can easily distinguish such isomers. 

The analytical technologies used In metabolomic investigations are nuclear magnetic resonance and mass spectrometry alone or in combination with liquid or gas chromatographic separation of metabolites (243). Other techniques include thin-layer chromatography, Fourier-transform infrared spectrometry, metabolite arrays, and Raman spectroscopy. 

UV detection is quite common, but in many cases it is not sufficiently selective even combined with chromatography, it often leads to false-positive or falsenegative results. For this reason many other types of detectors are used in analytical chemistry, to increase selectivity, specificity, or sensitivity. To identify or determine the molecular structure, the use of spectroscopic techniques is common. Mass spectrometry, the main topic of this book, is among the most commonly used and highest performance methods. Infrared spectroscopy (IR) and NMR are also often used, although the relatively low sensitivity of NMR restricts its use in the biomedical field. 

It must be emphasised that infrared and Raman spectroscopy should not be used to the exclusion of other techniques such as H and C nuclear magnetic resonance, which are particularly useful characterisation techniques. Other useful techniques are mass spectroscopy, ultraviolet-visible spectroscopy, chromatography, thermo-analytical techniques (such as differential scanning calorimetry (DSC), thermal gravimetry (TG) etc.), or combined techniques such as GC-MS (gas chromatography combined with mass spectrometry)... 

Near Infrared Reflectance Analysis (NIRA) is in use at over 5000 sites for the analysis of multiple constituents in food and other products. The technology is based upon correlation transform spectroscopy, which combines NIR spectrophotometry and computerized analysis of a "learning set" of samples to obtain calibrations without the need for detailed spectroscopic knowledge of factors being analyzed. The computer can obtain spectral characteristics of the analyte (based upon a correlation with data from an accepted reference analysis) without separation of the sample s constituents. 

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