Other Nondestructive Quantitation Methods

If a soluble reagent containing an ultraviolet (UV)-active group or dye can be used, then it may be possible to estimate the reaction yield from the amount of unreacted reagent stiU remaining in the supernatant solution at the end of the reaction. For example, the derivatization of aldehydes and ahphatic ketones with dansylhydrazine has been monitored by fluorescence spectroscopy of the supernatant solution, and has been used to quantify the amount of supported aldehyde or ketone. 

An alternative approach is the cleavage of a UV-active protecting group from the resin, such as the widely used Fmoc Test. The quantitation of the 9-fluorenyl-methyloxycarbonyl (Fmoc) protecting group for amines is used in SPPS as an indirect method to determine the extent of a peptide coupling reaction. Similar approaches have also been recently reported for the quantitation of supported thiols [151, 154] and have also been the subject of an excellent review [148]. 

More recently, the synthesis of a novel dihydropyran with a UV-handle has also been reported as a protecting group for supported alcohols [155]. 

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Nuclear reaction analysis (NRA) is used to determine the concentration and depth distribution of light elements in the near sur ce (the first few lm) of solids. Because this method relies on nuclear reactions, it is insensitive to solid state matrix effects. Hence, it is easily made quantitative without reference to standard samples. NRA is isotope specific, making it ideal for isotopic tracer experiments. This characteristic also makes NRA less vulnerable than some other methods to interference effects that may overwhelm signals from low abundance elements. In addition, measurements are rapid and nondestructive. 

A rapid, nondestructive method based on determination of the spatial distribution of ATP, as a potential bioindicator of microbial presence and activity on monuments, artworks, and other samples related to the cultural heritage, was developed [57], After cell lysis, ATP was detected using the bioluminescent firefly luciferin-luciferase system and the method was tested on different kinds of surfaces and matrices. Figure 3 reports the localization of biodeteriogen agents on a marble specimen. Sample geometry is a critical point especially when a quantitative analysis has to be performed however, the developed method showed that with opti-... 

Near infrared spectroscopy (NIRS), a technique based on absorption and reflectance of monochromatographic radiation by samples over a wavelength range of 400-2500 run, has been successfully applied for food composition analysis, for food quality assessment, and in pharmaceutical production control. NIRS can be used to differentiate various samples via pattern recognitions. The technique is fast and nondestructive method that does not require sample preparation and is very simple to use compared too many other analytical methods such as HPLC. The drawback of NIRS, however, is that the instrument has to be calibrated using a set of samples typically 20-50 with known analyte concentrations obtained by suitable reference methods such as FIPLC in order to be used for quantitative analyses. Simultaneous quantification of the... 

Spectroscopic methods are nondestructive and can be used in conjunction with other solid-state techniques (TGA, microscopy, DSC, XRD) for the quantitative analysis of... 

This procedure is thus properly called an X-ray fluorescence, or X-ray emission method. X-ray fluorescence (XRF) is a powerful tool for rapid, quantitative determinations of all but the lightest elements. In addition, XRF is used for the qualitative identification of elements having atomic numbers greater that of oxygen (>8) and is often used for semiquantitative or quantitative elemental analyses. A particular advantage of XRF is that it is nondestructive, in contrast to most other elemental analysis techniques. 

Near-infrared (NIR) spectrometry is an instrumental method for acquiring spectra of foods and other materials. The acquired spectra are used for determining both qualitative and quantitative characteristics. NIR spectrometry is popular because of its four main advantages speed (a spectrum can be acquired in as little as a tenth of a second), little or no sample preparation (if any preparation is required, it is usually quite simple), multiple analyses from a single scan (it is not necessary to scan the sample for each constituent), and a nondestructive measurement process (allowing for the return of the analyzed subsample to the original lot) (28). 

Hardness is a measurement of material resistance to plastic deformation in most cases. It is a simple nondestructive technique to test material indentation resistance, scratch resistance, wear resistance, or machinability. Hardness testing can be conducted by various methods, and it has long been used in analyzing part mechanical properties. In reverse engineering, this test is also widely used to check the material heat treatment condition and strength, particularly for a noncritical part, to save costs. The hardness of a material is usually quantitatively represented by a hardness number in various scales. The most utilized scales are Brinell, Rockwell, and Vickers for bulk hardness measurements. Knoop, Vickers microhardness, and other microhardness scales are used for very small area hardness measurements. Rockwell superficial and Shore scleroscope tests are used for surface hardness measurements. Surface hardness can also be measured on a nanoscale today. 

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