Flame emission photometry spectrometry

The concentration of lithium in serum, plasma, urine, or other body fluids has been determined by flame emission photometry, atomic absorption spectrometry, or electro-chemically using an ion-selective electrode. Serum analysis, the most useful specimen for lithium monitoring, is most commonly quantified by automated spectrophotometric assay. 

Atomic absorption spectrometry is one of the most widely used techniques for the determination of metals at trace levels in solution. Its popularity as compared with that of flame emission is due to its relative freedom from interferences by inter-element effects and its relative insensitivity to variations in flame temperature. Only for the routine determination of alkali and alkaline earth metals, is flame photometry usually preferred. Over sixty elements can be determined in almost any matrix by atomic absorption. Examples include heavy metals in body fluids, polluted waters, foodstuffs, soft drinks and beer, the analysis of metallurgical and geochemical samples and the determination of many metals in soils, crude oils, petroleum products and plastics. Detection limits generally lie in the range 100-0.1 ppb (Table 8.4) but these can be improved by chemical pre-concentration procedures involving solvent extraction or ion exchange. 

FLAME PHOTOMETRY AND SPECTROMETRY. The basic principle of flame emission spectrometry rests on the fact that salts of metals, when introduced under carefully coni rolled condiiions imo a suitable flame, are vaporized and excited to emit radiations that are characteristic for each clement. Correlation of the emission intensity with the concentration of that clement forms the basis of quantitative evaluation. 

Potassium can be determined by flame emission spectrometry (flame photometry) using a lithium internal standard. The following data were obtained for standard solutions of KCl and an unknown containing a constant known amount of LiCl as the internal standard. All the intensities were cor-... 

In the early years of flame photometry, only relatively cool flames were used. We shall see below that only a small fraction of atoms of most elements is excited by flames and that the fraction excited increases as the temperature is increased. Consequently, relatively few elements have been determined routinely by flame emission spectrometry, especMly j ew of those that emit line spectra (several can exist in flames as molecular species, particularly as oxides, which emit molecular band spectra). Only the easily excited alkali metals sodium, potassium, and lithium are routinely deterniined by flame emission spectrometry in the clinical laboratory. However, with flames such as oxyacetylene and nitrous oxide-acetylene, over 60 elements can now be determined by flame emission spectrometry. This is in spite of the fact that a small fraction of excited atoms is available for emission. Good sensitivity is achieved because, as with fluorescence (Chapter 16), we are, in principle, measuring the difference between zero and a small but finite signal, and so the sensitivity is limited by the response and stability of the detector and the stability (noise level) of the flame aspiration system. 

A technique closely related to flame emission spectrometry is atomic absorption spectrophotometry (AAS) because they each use a flame as the atomizer. We discuss here the factors affecting absorption and because of the close relationship of atomic absorption and flame photometry, we shall make comparisons between the two techniques where appropriate. 

Emission spectrometry using chemical flames (flame atomic emission spectrometry, FAES) as excitation sources is the earlier counterpart to flame atomic absorption spectrometry. In this context emission techniques involving arc/spark and direct or inductively coupled plasma for excitation are omitted and treated separately. Other terms used for this technique include optical emission, flame emission, flame photometry, atomic emission, and this technique could encompass molecular emission, graphite furnace atomic emission and molecular emission cavity analysis (MEGA). 

FP, flame photometry FAAS, flame atomic absorption spectrometry ETAAS, electrothermal atomic absorption spectrometry ICP-AES, inductively coupled plasma-atomic emission spectrometry ICP-MS, inductively coupled plasma-mass spectrometry HG, hydride generation CV, cold vapor AFS, atomic fluorescence spectrometry ASV, anodic stripping voltammetry PSA, potentiometric stripping... 

The sensitivity of detection of some 70 elements by flame emission or absorption spectrometry can, in many instances, be very low. The level of detection of sodium by flame photometry is often limited by the residual content of the water or other solvent used for the sample e.g., 1 ng/g of sodium can be detected without difficulty. Detection limits reported for other elements range from 1 to 1000 ng/g by one or the other of these two techniques. The potential capabilities of these methods have been considerably improved by the introduction of nonflame techniques. ... 

Instrumentation. Flame Characteristics. Flame Processes. Emission Spectra. Quantitative Measurements and Interferences. Applications of Flame Photometry and Flame Atomic Emission Spectrometry. 

The basic instrumentation used for spectrometric measurements has already been described in the previous chapter (p. 277). Methods of excitation, monochromators and detectors used in atomic emission and absorption techniques are included in Table 8.1. Sources of radiation physically separated from the sample are required for atomic absorption, atomic fluorescence and X-ray fluorescence spectrometry (cf. molecular absorption spectrometry), whereas in flame photometry, arc/spark and plasma emission techniques, the sample is excited directly by thermal means. Diffraction gratings or prism monochromators are used for dispersion in all the techniques including X-ray fluorescence where a single crystal of appropriate lattice dimensions acts as a grating. Atomic fluorescence spectra are sufficiently simple to allow the use of an interference filter in many instances. Photomultiplier detectors are used in every technique except X-ray fluorescence where proportional counting or scintillation devices are employed. Photographic recording of a complete spectrum facilitates qualitative analysis by optical emission spectrometry, but is now rarely used. 

Applications of Flame Photometry and Flame Atomic Emission Spectrometry... 

A number of instrumental analytical techniques can be used to measure the total phosphorus content of organophosphorus compounds, regardless of the chemical bonding of phosphorus within the molecules, as opposed to the determination of phosphate in mineralized samples. If the substances are soluble, there is no need for their destruction and for the conversion of phosphorus into phosphate, a considerable advantage over chemical procedures. The most important methods are flame photometry and inductively coupled plasma atomic emission spectrometry the previously described atomic absorption spectrometry is sometimes useful. 

An official method has been published for the determination of nickel in 1M ammonium nitrate extracts of potassium from soil [178]. The level of potassium in the extract is determined by flame photometry. Inductively coupled plasma atomic emission spectrometry (Sect. 2.55) and stable isotope dilution (Sect. 2.55) have been applied to the determination of potassium in multi-metal analyses. 

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. 

Each spectroscopic method has a characteristic application. For example, flame photometry is still applicable to the direct determination of Ca and Sr, and to the determination of Li, Rb, Cs and Ba after preconcentration with ion-exchange resin. Fluorimetry provides better sensitivities for Al, Be, Ga and U, although it suffers from severe interference effects. Emission spectrometry, X-ray fluorescence spectrometry and neutron activation analysis allow multielement analysis of solid samples with pretty good sensitivity and precision, and have commonly been applied to the analysis of marine organisms and sediments. Recently, inductively-coupled plasma (ICP)... 

APPLICATIONS OF FLAME PHOTOMETRY . /lND FLAME - ATOMIC EMISSION SPECTROMETRY... 

This article focuses primarily on traditional low-temperature flame photometry. High-temperature flame photometry has evolved into separate techniques, typically identified by their temperature sources (e.g., inductively coupled plasma-atomic emission spectrometry, ICP-AES ). Some references to other related analytical tools, including high-temperature flame photometry, are made here to establish perspective. 

Separation gas chromatography, liquid chromatography, electrophoresis. Detection electron capture, nitrogen phosphorus, flame ionization, flame photometry, fluorescence, diode array, UV, mass spectrometry Atomic spectrometry (absorption, emission, fluorescence), mass spectrometry, polarography, voltammetry... 

Instrumentation. Flame characteristics. Flame processes. Emission spectra. Quantitative measurements and interferences. Applicaiion.s of flame photometry and flame atomic emission spectrometry. 

Absorption spectrophotometry Fluorescence methods Atomic-absorption methods Flame photometry Neutron activation analysis Emission spectroscopy Spark source mass spectrometry Reaction gas chromatography of chelates using electron-capture detection... 

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