Spectroscopy without sampling

Mossbauer Effect Spectroscopy without Sampling Application to Art and Archaeology... 

Keisch, B., Mossbauer Effect Spectroscopy Without Sampling Applica-... 

Another approach is to perform ex situ reactions and insert the sample into a high vacuum system without exposure to ambient conditions. Incorporating N2 glove boxes or reactor systems with X-ray photoelectron spectroscopy (XPS) sample handling can also provide information that is closer to operational conditions. In a similar manner ex situ reactions and sample handling are starting to be apphed to electron microscopy studies. Commercially available sample transfer systems will accelerate the application of this methodology. 

In contrast, methods such as photoelectron spectroscopy (ESCA) analyze the entire sample content without sample preparation. However, ESCA is a surface technique, and the sample is exposed to vacuum and X-ray bombardment during analysis. ESCA results therefore may not be representative of the bulk composition some volatile species may be lost because of the vacuum, and in principle the X-ray bombardment may cause chemical changes of some species. 

Solid-state NMR spectroscopy is arguably the most commonly applied NMR technique in the study of NOM structure because whole soil or sediment analysis can be performed without sample extraction. The 13C nucleus is typically the focus of NOM solid-state NMR studies because strong 1H-1H dipolar interactions (which cannot be easily overcome experimentally) in the solid state result in extremely broad lines. However, because the natural abundance of the 13C isotope is only -1.13% of the total carbon present, observing 13C signals directly is often difficult. 

Analogously, LC/MS is useful for screening of the degradation products, and here, no derivatization is required. Screening by 31P 1H and/or 19F NMR spectroscopy can reveal phosphorus- and fluorine-containing chemicals. One advantage of LC/MS and NMR over GC-relying techniques is the ability to separate (in LC/MS) and detect polar, nonvolatile analytes without sample pretreatment and derivatization. 

The main advantage of ATR spectroscopy is the possibility of carrying out measurements without sample preparation, as the resin beads are pressed directly onto the ATR... 

Elemental speciation using mass spectrometry in conjunction with ICPAES is a latest advance in atomic spectroscopy, which is becoming popular in analytical research labs. Mason et al. ExxonMobil Research and Engineering) show how linking ICP-MS to various liquid chromatographic techniques has enabled determination of ppm levels of metals in hydrocarbons to ppb level measurements in refinery effluent streams. Hyphenated ICP-MS techniques were used to provide speciation information on nickel and vanadium in crude oils and assist in development of bioremediation options for selenium removal in wastewater treatment plants. Similar ICP-MS technique without sample demineralization was used by Lienemann, et al. Institut Francais du Petrole) to determine the trace and ultra-trace amounts of metals in crude oils and fractions. 

Hydrocarbon streams have also been investigated and Raman-using systems have been patented. The monitoring of emulsion polymerizations by Raman spectroscopy is also proposed. Pharmaceutical process applications of Raman spectroscopy include the monitoring of the active ingredient in a product without sample preparation. The identification of gemstones and the determination of the synthetic/natural origins are well known. 

Alternatively, samples can be withdrawn from the reactor and analyzed for residual monomer in solution at various times by chromatographic or spectroscopic techniques. Sample removal techniques can be very difficult, especially since many reactions are extremely sensitive to oxygen and other impurities that can be introduced during sampling. In situ infrared spectroscopy is a state-of-the-art, real-time, monitoring technique that is well suited to obtain real-time structural and kinetic information of polymerization processes without sampling. In addition, reactions are analyzed without complicated reactor modifications or expensive deuterated monomers. 

ATR accessory can also be employed for reflectance analysis, particularly for the surfaces of smears sticking on a given support with, e.g., SplitPea accessory (Flarrick Scientific Corporation) very small paint traces can be measured (<0.3 mm) without sample preparation, on the basis of internal reflection, external reflection, or in-line diffuse reflection spectroscopy. 

Surfactants, hydrotropes, and sequestering agents are analyzed without sample pretreatment in liquid detergent by NMR spectroscopy and phosphorus species present in detergents are quantified by NMR spectrometry. 

Specular reflectance spectroscopy in mid-IR allows identification of non-coated technical thermoplastics without sample preparation in just a few seconds. First derivative spectra permit to distinguish various filler types (talcum, chalk or barium sulfate) in PR Identification of fiame retardants, which is important for the sorting process of used computer displays or TV sets, is very complex in view of the wide variety of FRs. It is possible, however, to detect specific FRs in certain polymers by mid-IR reflectance techniques, for example polybromi-nated diphenylethers (PBDE) in ABS. This technique probably has limited applicability only. 

Mirabella and Koberstein have previously shown the benefit of DSC/FT-IR for polymer characterization (3,4). In this work, the same epoxy system described above in the uncured state was analyzed by DSC/FT-IR. Thin films of uncured amine-activated epoxies were placed in the sample pan of the FP84 and heated from 25 to 280 °C at 10 C per minute. Changes in the structure of the epoxy as a fimction of temperature were recorded simultaneously by infrared spectroscopy. The sample was relatively transmissive to infirared radiation. The beam transmitted down through the sample, reflected off the aluminum cup, and passed back up through the material. This type of analysis is called reflection/absorption spectroscopy. A "well behaved" absorbance spectrum was generated directly without any need for correction. To produce a sufficient signal on the DSC, the bulk of the sample had to be placed on the reference side. 

It is remarkable that the simple use of squares of directional cosines (the X values sometimes equivalent quantities are used, the Saupe S matrices and the order parameters) provides a description of all directional properties of the sample, which can be observed in absorption spectroscopy, without any assumptions. Several alternative descriptions (the Eraser-Beer model, the Tanizaki model, the Popov model) involve assumptions that are rarely fulfilled. At the same time, some of these models tend to be mathematically complex. A simple extension of the... 

Rodger et al. (1998) demonstrated the use of surface-enhanced resonance Raman scattering (SERRS) spectroscopy, without any separation procedure, to analyze dyes and pigments in lipsticks. Lipsticks smeared on glass and cotton surfaces required treatment with a surfactant, for example, poly(L-lysine), and silver colloid prior to the analysis. This in situ SERRS method was applied to six commercial lipstick samples. Discrimination between the samples and identification of some of the pigments present were achieved. The method is qualitative in nature and was suggested to have potential for forensic and quality-control applications. 

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