Spectroscopic analysis Atomization Atomic Absorption

Spectroscopic Methods of Analysis Atomic Absorption and Emission Spectrophotometry... 

Solubilization of Drugs in Aqueous Media / 3311 Solubilizing Excipients in Pharmaceutical Formulations / 3334 Spectroscopic Methods of Analysis Atomic Absorption and Emission Spectrophotometry / 3367... 

Ion chromatography plays a very important role in hyphenated techniques used in species analysis. Coupling techniques represent the link of ion chromatography systems with an independent analytical detection method, usually spectroscopic (AAS-Atomic Absorption Spectroscopy, ICP-AES-lnductively Coupled Plasma Atomic Emission Spectroscopy, ICP-MS-Inductively Coupled Plasma-Mass Spectrometry ). 

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. 

Several spectroscopic techniques have been apphed to determine surfactants in cosmetics with different aims conventional infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) for qualitative analysis near infrared spectroscopy (NIR) and attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) for quantitative analysis atomic absorption spectroscopy (AAS) to determine specific surfactants. Mass... 

Finally, analytical methods can be compared in terms of their need for equipment, the time required to complete an analysis, and the cost per sample. Methods relying on instrumentation are equipment-intensive and may require significant operator training. For example, the graphite furnace atomic absorption spectroscopic method for determining lead levels in water requires a significant capital investment in the instrument and an experienced operator to obtain reliable results. Other methods, such as titrimetry, require only simple equipment and reagents and can be learned quickly. 

Although the most sensitive line for cadmium in the arc or spark spectmm is at 228.8 nm, the line at 326.1 nm is more convenient to use for spectroscopic detection. The limit of detection at this wavelength amounts to 0.001% cadmium with ordinary techniques and 0.00001% using specialized methods. Determination in concentrations up to 10% is accompHshed by solubilization of the sample followed by atomic absorption measurement. The range can be extended to still higher cadmium levels provided that a relative error of 0.5% is acceptable. Another quantitative analysis method is by titration at pH 10 with a standard solution of ethylenediarninetetraacetic acid (EDTA) and Eriochrome Black T indicator. Zinc interferes and therefore must first be removed. 

There are two themes in this work (1) that all soil is complex and (2) that all soil contains water. The complexity of soil cannot be overemphasized. It contains inorganic and organic atoms, ions, and molecules in the solid, liquid, and gaseous phases. All these phases are both in quasi equilibrium with each other and are constantly changing. This means that the analysis of soil is subject to complex interferences that are not commonly encountered in standard analytical problems. The overlap of emission or absorption bands in spectroscopic analysis is but one example of the types of interferences likely to be encountered. 

Of particular concern in this analysis is sodium because it destroys soil structure, is associated with increased soil pH, and can be toxic to plants. Sodium can easily be determined by atomic absorption spectroscopy (AAS), flame ionization spectroscopy (FIS), and inductively coupled plasma (ICP) methods. Soil structure is discussed in Chapter 2 and the various spectroscopic methods discussed in Chapter 14. 

Atomic absorption and inductively coupled plasma spectrometers are metal-selective spectrometers used for organic metal analysis. The connection of these spectroscopic instruments to a liquid chromatograph is relatively simple. Chromatograms of alkylmercury3 and aminoplatinum analytes4 are shown in Figures 2.8 and 2.9, respectively. 

The element may be analyzed in aqueous acidified phase by flame and furnace atomic absorption, ICP emission and ICP-MS spectroscopic methods. Also, at trace concentrations the element may be measured by x-ray fluorescence and neutron activation analysis. Wavelength for AA measurement is 240.7 nm and for ICP analysis is 228.62 nm. 

A lead blank (500 L of distilled water containing 25 /xg/L of Pb(N03)2) was pumped onto the ion-exchange columns only. The aqueous eluents were combined with the acetonitrile eluant for each column NaCl was added to separate the aqueous and organic phases. After separation, the aqueous phase was extracted twice with acetonitrile. The extracts from each column were pooled and reduced in Kuderna-Danish evaporators to a final acetonitrile volume of 4-6 mL and then diluted to a known volume with distilled water for atomic absorption spectroscopic (AAS) determination of lead. AAS analysis was on an IL 951 with an air-acetylene flame the 217.0-nm lead line was used. 

Spectroscopic analysis can also benefit from a preceding electrochemical preconcentration. In particular, such coupling has been widely used for minimizing matrix interferences in atomic absorption spectroscopy (AAS). For example, lead, nickel, and cobalt have been determined in seawater with no interferences from the high sodium chloride content [80]. By adjusting the deposition potential and the pH, it is possible to obtain information on the oxidation and com-plexation states of the metal ions present [81]. 

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. 

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