Flame photometry atomic absorption

Flame Photometry, Atomic Absorption, and Neutron Activation. Comparatively few substances amenable to measurement by these techniques are used therapeutically chief among those that are being sodium, potassium, lithium, calcium, magnesium, zinc, copper, and iron, for all of which one or other of the techniques is the method of choice. 

Sodium and potassium may be quantified by flame photometry, atomic absorption spectroscopy or ion specific electrodes. 

This is a non-SI weight per volume (w/v) concentration term commonly used in quantitative analysis such as flame photometry, atomic absorption spectroscopy and gas chromatography, where low concentrations of solutes are to be analysed. The term ppm is equivalent to the expression of concentration as /igrnL" (10 gmL ) and a l.Oppm solution of a substance will have a concentration of 1.0/igmL (1.0 x 10 gmL ). A typical procedure for calculations in terms of ppm is shown in Box 6.2. 

Figure 1 represents four examples of the evaluation of measurement uncertainty for potassium, calcium, magnesium and glucose using flame photometry, atomic absorption spectrometry and molecular spectrometry (Mg determination with Titan Yellow and glucose determination with glucose oxidase). For the sake of simplicity in Fig. 1, the component of uncertain-... 

Flame photometry Atomic absorption spectrometry Amperometry/coulometry Indirect potentiometry... 

The essential difference between K-Ar and Ar-Ar dating techniques lies in the measurement of potassium. In K-Ar dating, potassium is measured generally using flame photometry, atomic absorption spectroscopy, or isotope dilution and Ar isotope measurements are made on a separate aliquot of the mineral or rock sample. In Ar-Ar dating, as the name suggests, potassium is measured by the transmutation of to Ar by neutron bombardment and the age calculated on the basis of the ratio of argon isotopes. 

Introduction Separation Methods Chromatographic Separations Gas Chromatography High-Performance Liquid Chromatography Basis for Spectral Methods Fluorometry Flame Photometry Atomic Absorption Spectroscopy Turbidimetry and Nephelometry Defining Terms References... 

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. 

General Discussion and Elementary Theory of Flame Spectrometry (Atomic Absorption Spectrometry and Flame Photometry)... 

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). 

Instrumental Quantitative Analysis. Methods such as x-ray spectroscopy, oaes, and naa do not necessarily require pretreatment of samples to soluble forms. Only reUable and verified standards are needed. Other instmmental methods that can be used to determine a wide range of chromium concentrations are atomic absorption spectroscopy (aas), flame photometry, icap-aes, and direct current plasma—atomic emission spectroscopy (dcp-aes). These methods caimot distinguish the oxidation states of chromium, and speciation at trace levels usually requires a previous wet-chemical separation. However, the instmmental methods are preferred over (3)-diphenylcarbazide for trace chromium concentrations, because of the difficulty of oxidizing very small quantities of Cr(III). 

All the alkali metals have characteristic flame colorations due to the ready excitation of the outermost electron, and this is the basis of their analytical determination by flame photometry or atomic absorption spectroscopy. The colours and principal emission (or absorption) wavelengths, X, are given below but it should be noted that these lines do not all refer to the same transition for example, the Na D-line doublet at 589.0, 589.6 nm arises from the 3s — 3p transition in Na atoms formed by reduction of Na+ in the flame, whereas the red line for lithium is associated with the short-lived species LiOH. 

The ratio, Nj/N0, can therefore be calculated. For the relatively easily excited alkali metal sodium, it is 9.9 x 10 6 at 2000 °K and 5.9 x 10 4 at 3000 °K this latter temperature is about the highest commonly obtained with flames used for atomic absorption or emission work. Hence, only about 1(T3 % of the sodium atoms are excited at 2000 ° and 6 x 1(F2 % at 3000°. For an element such as zinc,Nf/N0 is 5.4 x 10"10 at 3000 and so only 5 x 10"8% is excited. In spite of the small fraction excited, good sensitivities can be obtained for many elements by flame photometry if a high temperature flame is used, because the difference between zero and a small but finite number is measured. For example, seventy elements can be determined by flame photometry using the nitrous oxide-acetylene flame 1H. 

Atomic absorption takes advantage of the fact that most of the atoms remain in the ground state, and are capable of absorbing radiation of the appropriate wavelength corresponding to Ah. Whereas a hot flame is preferred for flame photometry, a cooler flame is preferred for atomic absorption, except in cases where chemical interference may occur. 

Nixon277 compared atomic absorption spectroscopy, flame photometry, mass spectroscopy, and neutron activation analysis as methods for the determination of some 21 trace elements (<100 ppm) in hard dental tissue and dental plaque silver, aluminum, arsenic, gold, barium, chromium, copper, fluoride, iron, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, tin, strontium, vanadium, and zinc. Brunelle 278) also described procedures for the determination of about 20 elements in soil using a combination of atomic absorption spectroscopy and neutron activation analysis. 

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. 

Even in these cases, over 90% of such atoms are likely to remain in the ground state if cooler flames, e.g. air-propane, are used (Table 8.7). The situation should be contrasted with that encountered in flame photometry which depends on the emission of radiation by the comparatively few excited atoms present in the flame. However, because of fundamental differences between absorption and emission processes it does not follow that atomic absorption is necessarily a more sensitive technique than flame emission. 

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 atomic absorption spectrometry has achieved very wide use as a routine method for the determination of trace metals in solution. However, for alkali metals flame photometry has remained popular. Why is this ... 

What do the letters ICP stand for Is the ICP technique more closely related to atomic absorption or flame photometry Explain. 

Compare atomic absorption (both flame and graphite furnace), ICP, flame photometry, cold vapor mercury, hydride generation, atomic fluorescence, and spark emission in terms of ... 

Whereas flame emission photometry relies on the excitation of atoms and the subsequent emission of radiation, atomic absorption spectrophotometry relies on the absorption of radiation by non-excited atoms. Because the proportion of the latter is considerably greater than that of the excited atoms, the potential sensitivity of the technique is also much greater. 

Atomic absorption spectroscopy is highly specific and there are very few cases of interference due to the similar emission lines from different elements. General interference effects, such as anionic and matrix effects, are very similar to those described under flame emission photometry and generally result in reduced absorbance values being recorded. Similarly, the use of high temperature flames may result in reduced absorbance values due to ionization effects. However, ionization of a test element can often be minimized by incorporating an excess of an ionizable metal, e.g. potassium or caesium, in both the standards and samples. This will suppress the ionization of the test element and in effect increase the number of test atoms in the flame. 

Five liquid membrane electrodes (Table 13.3) are now commercially available and have found wide application in the testing of electrolytes in biological and technological systems. All five electrodes perform well in the concentration range over which the Nernstian slope is maintained, i.e., from 10 -10 moldm . These electrodes to a certain extent have replaced in both chemical and clinical laboratories the more traditional instrumental methods of analysis, such as flame photometry and atomic absorption spectrometry. There are, of course, many more liquid membrane electrodes, but the availability of satisfactory solid electrodes has greatly restricted their development and practical application. 

L8. Levy, A. L., and Katz, E. M., A comparison of serum lithium determinations using flame photometry and atomic absorption spectrophotometry. Clin. Chem. 16, 840-842 (1970). 

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. 

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