Sample spectroscopy

Optical Spectroscopy Sampling Techniques Manual. Harrick Scientific Corporation Ossining, N.Y., 1987. 

Sample preparation is straightforward for a scattering process such as Raman spectroscopy. Sample containers can be of glass or quartz, which are weak Raman scatterers, and aqueous solutions pose no problems. Raman microprobes have a spatial resolution of - 1 //m, much better than the diffraction limit imposed on ir microscopes (213). Eiber-optic probes can be used in process monitoring (214). 

Minimal sample preparation is involved in Raman spectroscopy samples as thin as a monolayer can be examined. 

In mass spectroscopy, sample molecules are ionized and the different masses of the ions formed are selected by use of an electric or magnetic field. In its simplest form, a mass spectrometer is an instrument that measures the mass-to-electric charge ratios of ions formed when a sample is ionized. If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the mass-to-electric charge ratio of the ions gives a direct measurement of the weight of the molecule (de Hoffmann and Stroobant 2001). 

In order to more accurately identify the contaminant, and to determine if the fuel delivery system module filter was the source, both materials were analyzed using 1H NMR spectroscopy Samples were dissolved in a 60 40 mixture of deuterated chloroform/triflouroethanol. It should be noted that the amount of contaminant available for analysis was quite small, so for this sample, the NMR spectral acquisition time was set to 1 h in order to record a spectrum of adequate signal-to-noise ratio. 

Pontanen and Morris [8] compared the structure of humic acids from marine sediments and degraded diatoms by infrared and C13 and proton NMR spectroscopy. Samples of marine sediments taken from the Peru continental shelf were extracted with water, sodium hydroxide (0.05mol 1 J) and sodium pyrophosphate (0.05mol l-1) under an atmosphere of nitrogen and fractionated by ultrafiltration. Humic acids of molecular weight 300000 and above were examined. Diatoms were collected from... 

IR Spectroscopy. Samples of the hexane layer (8-4, 4-4, 2-4, 1-4), after evaporation of the solvent, gave IR spectra of mixtures of TBTC1 and TBTA. The amount of TBTA depended on the concentration of sodium chloride solution and its volume, as evidenced by the intensity of the broad peak at 1650 cm-1. 

In Table IV we present Eai and Ei0 data on two important deep centers in GaAs, Cr, and O (EL2). The results from three different laboratories are included, but no attempt was made to show everything available in the literature. It is clear that neither the Eai results nor the Ei0 results agree well for Cr, but are not too bad for O. In contrast, the TDH measurements of El0, shown in Table II, are much more consistent. It should be noted that the TDH samples (Table II) were semi-insulating, whereas the emission-spectroscopy samples (Table IV) were conducting in order that capacitance transient (DLTS) experiments could be performed. The PITS and OTCS techniques applied to these samples would have been unable to clearly distinguish between hole and electron traps. 

I n atomic spectroscopy, samples are vaporized at 2 000-8 000 K and decompose into atoms. Concentrations of atoms in the vapor are measured by emission or absorption of characteristic wavelengths of radiation. Because of its high sensitivity, its ability to distinguish one element... 

Electrons can be made to resonate between these two states by the application of microwave energy. In EPR spectroscopy samples are subjected to microwave radiation of constant frequency and the magnetic field strength is increased until energy absorption is detected - this occurs when the energy difference between the two spin states matches the energy of the microwave radiation. 

Claybourn, M., External Reflection Spectroscopy. In Chalmers, J.M. 8c Griffiths, P.R. (eds) Handbook of Vibrational Spectroscopy, Sampling Techniques, Volume 2 John Wiley 8t Sons Chichester, 2002 pp. 969-981. 

Electronic absorption spectroscopy Samples were examined in methanol or ethanol on a double-beam spectrophotometer, Model SP800B (Pye Unicam Instruments Ltd, Cambridge, U.K.)... 

Marked differences are seen between IR and Raman spectroscopy in sampling techniques. In IR spectroscopy, sampling techniques for routine measurements are relatively simple. In contrast, Raman sampling techniques are intricate and versatile, and individual workers employ a variety of sampling techniques developed for their needs. Some of these techniques are described below. 

IR Spectroscopy. Samples for IR spectroscopy were prepared by pressing 100-mg KBr pellets containing 1 mg of sample. Samples were run both on a Perkin-Elmer model 167 dispersive (grating) instrument and on a Perkin-Elmer model 1750 Fourier transform diffractometer-model 7300 laboratory computer system. Only the latter instrument afforded the resolution needed to identify the skeletal frequencies of isopropyl groups. 

In EPR spectroscopy, samples are brought into a homogeneous external magnetic field. The electron spin vector of the paramagnetic species in the sample can only take on distinct orientations with respect to the direction of this external field. 

Fig. 10 Vessel for preparation of soluble polyanions and polyradicals for SQUID magneto-metry (tube A), EPR spectroscopy (tube B), SANS (cylindrical cell C), and NMR spectroscopy (sample tube not shown) (a) sample compartment with Teflon-coated magnetic stir-bar, (b) glass frit (course), (c) pyrex-to-quartz seal, (d) thin bottom ( 6 cm from the end of the tube). Solv-seal joints and Kontes (or Chemglass) vacuum stopcocks are used. Reproduced with permission from Ref. 94. Copyright 2004 Am. Chem. Soc.

Dynamic Mechanical Spectroscopy. Samples were run in the tensile mode using a Rheometrics Model 605 Mechanical Spectrometer. Temperature scans were run from -160 to 240 C using a strain of 0.15% and a frequency of 1 Hertz. Samples were maintained in a nitrogen atmosphere during testing. 

Culler, S. R., Diffuse Reflectance Infrared Spectroscopy Sampling Techniques for Qualita-tive/Quantitative Analysis of Solids. In Polymorphism in Pharmaceutical Solids Brittain, H. G., Ed. Marcel Dekker New York 1999, pp. 93. 

We have examined the microstructure of a number of dichlorocarbene adducts of both cis- and trans-polybutadiene using 13C NMR spectroscopy. Samples were prepared in a two phase system where dichlorocarbene was generated by the reaction of either concentrated aqueous or solid alkali metal hydroxide with chloroform in the presence of a phase transfer catalyst (14t). Monomer compositions and sequence lengths were obtained as for true copolymers and were correlated with glass transition temperature and phase morphology. 

The most widely available technique for identifying mainly polymer, but also additives in plastics, is Fourier Transform Infrared (FTIR) spectroscopy. Samples are exposed to infrared light (4000-400 wavelengths per centimetre or cm ) causing chemical bonds to vibrate at specific frequencies, corresponding to particular energies. In the last 5 years, an accessory for FTIR has been developed, which enables non-destructive examination of surfaces and so is ideal for analysis of plastics in museum collections. Attenuated Total Reflection-FTIR (ATR-FTIR) requires samples to be placed on a diamond crystal with a diameter of 2 mm through which the infrared beam is reflected... 

GDMS Glow Discharge Mass Spectroscopy Sample forms the cathode for a D.C. glow discharge Sputtered atoms ionized in plasma Ions - analyzed in mass spectrometer 0.1-100 pm 3-4 mm (Bulk) trace element analysis deleclion limit sub-ppb 9,10... 

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