Spectroscopic analysis Absorption Spectrometry

GFAAS = graphite furnace (flameless) atomic absorption spectroscopy TLC = thin layer chromatography HFP-AES = high frequency plasma-atomic emission spectroscopy NAA = neutron atomic analysis ICP-AES = inductively coupled plasma-atomic emission spectroscopy AAS = atomic absorption spectrometry GSE = graphite spectroscopic electrode UV = ultraviolet spectrophotometry PD = photodensitometer and (3,5-diBr-PADAP) = 2(-3,-5-dibromo-2-pyridylazo)-5- diethyl-ami nophenol. 

Various spectroscopic techniques such as flame photometry, emission spectroscopy, atomic absorption spectrometry, spectrophotometry, flu-orimetry, X-ray fluorescence spectrometry, neutron activation analysis and isotope dilution mass spectrometry have been used for marine analysis of elemental and inorganic components [2]. Polarography, anodic stripping voltammetry and other electrochemical techniques are also useful for the determination of Cd, Cu, Mn, Pb, Zn, etc. in seawater. Electrochemical techniques sometimes provide information on the chemical species in solution. 

Atomic absorption spectrometry (AAS) is a relatively new analytical technique among the spectroscopic methods. As described in the previous chapters, AAS gives high sensitivity, precision and accuracy along with experimental convenience and a wide instrumental availability. Therefore, this technique has been extensively employed for the analysis of marine samples. However, the elemental contents of marine samples are generally very low, and suitable preconcentration procedures are required. Recent development of graphite-furnace techniques and gas generation techniques has extended the applicability of AAS to marine analysis. The determination of Cd, Cu, Ni, Pb, Hg, As, Sb, Se, Sn and Te has become much easier as a result of the development of these techniques. 

The very low concentrations expected in the analysis of trace elements in offshore and coastal Antarctic sea water can be also detected thanks to the high detection power of spectroscopic techniques such as Electrothermal Atomic Absorption Spectrometry (ETA-AAS) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or ICP-MS. However, the saline matrix which constitutes the ideal medium in which to perform electrochemical measurements poses severe problems to the direct analysis of sea water because of possible signal suppression and/or undesired matrix effects. 

There are three main atomic spectroscopic techniques that are used for the analysis of acid digests atomic absorption spectrometry (AAS), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic fluorescence spectrometry (AFS). Of these, AAS and ICP-AES are the most widely used. Our discussion will deal with these techniques and also an affiliated technique, inductively coupled plasma mass spectrometry (ICP-MS). 

The earliest methods for tin analysis, namely, gravimetric and titrimetric methods, are now mainly of historical interest. Being essentially macro methods, laborious in application, they are limited and mainly useful for levels of tin in food in the 50-100 ppm range or above. The use of colorimetric analysis is associated with problems of specificity, sensitivity, and stability of the tin complexes formed. Nowadays, methods for tin analysis in biological media include the various atomic spectroscopic techniques (atomic absorption spectrometry, atomic emission spectroscopy, and inductively coupled plasma atomic emission spectrometry) as well as electrochemical and neutron activation procedures. 

Nearly every area of measurement science can boast of progress in measuring ever-smaller quantities of chemicals, but several stand out in their stunning trace-analysis capabilities. Trace-metal analysis has come to be dominated by methods that volatilize the sample and then either measure its spectroscopic emission or absorption, or measure the masses of the gaseous metal ions using mass spectrometry. Volatilization is accomplished by various thermal means that include flames, furnaces, and inductively coupled or microwave plasmas. The com-... 

As for silicon, secondary ion mass spectrometry (SIMS) is the most widely used profiling analysis technique for deuterium diffusion studies in III-V compounds. Deuterium advantageously replaces hydrogen for lowering the detection limit. The investigations of donor and acceptor neutralization effects have been usually performed through electrical measurements, low temperature photoluminescence, photothermal ionization spectroscopy (PTIS) and infrared absorption spectroscopy. These spectroscopic investigations will be treated in a separated part of this chapter. 

Capillary column gas chromatography is an even quicker and equally accurate alternative. Mass spectrometry (ASTM D1137) is also suitable for the analysis of petroleum gases. Of the other spectroscopic techniques, infrared and ultraviolet absorption may be applied to petroleum gas analysis for some specialized applications. Gas chromatography has also largely supplanted chemical absorption... 

Mass spectrometry (MS), also covered in this chapter, is not a spectroscopic technique, because it does not measure absorption or emission of light. A mass spectrometer bombards molecules with electrons and breaks the molecules into fragments. Analysis of the masses of the fragments gives the molecular weight, possibly the molecular formula, and clues to the structure and functional groups. Less than a milligram of sample is destroyed in this analysis. 

In both total and sequential dissolutions, the result is a solution containing the components of rocks and soils. This solution is then analyzed by different methods. Mostly, spectroscopic methods are used atomic absorption and emission spectroscopic methods, ultraviolet, atom fluorescence, and x-ray fluorescence spectrometry. Multielement methods (e.g., inductively coupled plasma optical emission spectroscopy) obviously have some advantages. Moreover, elec-troanalytical methods, ion-selective electrodes, and neutron activation analysis can also be applied. Spectroscopic methods can also be combined with mass spectrometry. 

Part V covers spectroscopic methods of analysis. Basic material on the nature of light and its interaction with matter is presented in Chapter 24. Spectroscopic instruments and their components are described in Chapter 25. The various applications of molecular absorption spectrometric methods are covered in some detail in Chapter 26, while Chapter 27 is concerned with molecular fluorescence spectroscopy. Chapter 28 discusses various atomic spectrometric methods, including atomic mass spectrometry, plasma emission spectrometry, and atomic absorption spectroscopy. 

More common methods for elemental analysis - to determine the elemental contents of a sample - include spectroscopy and spectrometry. Spectroscopy measures changes in atoms that cause a specific light photon to be either absorbed (absorption spectroscopy) or emitted (emission spectroscopy). This light has a precise wavelength or energy, characteristic of a specific element in the periodic table. The simplest (and oldest) form of elemental analysis was not spectroscopic, in fact, but colorimetric. This method was based on the reaction of a strongly colored chemical in a solution. The appearance of a specific color in the solution revealed the identity of the element of interest. If the color intensity is proportional to the amount of that element present, the method can also be used to estimate the amount of the element present. 

Chapter 11 details the relevant methods of analysis for both metals and organic compounds. For elemental (metal) analysis, particular attention is given to atomic spectroscopic methods, including atomic absorption and atomic emission spectroscopy. Details are also provided on X-ray fluorescence spectrometry for the direct analysis of metals in solids, ion chromatography for anions in solution, and anodic stripping voltammetry for metal ions in solution. For organic compounds,... 

Electrothermal atomic absorption represents a suitable instrumental technique for the analysis of elements in petroleum products [1-5]. The technique shows very low detection limits, similar to or even better than those found for other spectroscopic techniques, such as Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) [6] and ICP-Mass Spectrometry (ICP-MS) [7-12]. Some problems were evidenced in the use of ETAAS when elements like Ni [3] and Pb [13] are analyzed, due to the different behavior of organo-metallic species during the thermal treatment of standards and samples. 

Photothermal spectroscopy is a class of optical analysis methods that measures heat evolved as a consequence of light absorption in an irradiated sample. In conventional spectrometric methods information is obtained by measuring the intensities of light transmitted, reflected, or emitted by the sample. In photothermal spectrometry, spectroscopic information is obtained by measuring the heat accompanying non-radiative relaxation. Because of the universality of the photothermal effect (e.g., heat evolution accompanies essentially all optical absorption), photothermal spectroscopy has diverse applications in chemistry, physics, biology, and engineering. Some applications and measurements in the analysis of solids are reviewed here. 

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