Metals flame atomic absorption spectroscopy

The capacity factors of SN-SiO, for metal ions were determined under a range of different conditions of pH, metal ions concentrations and time of interaction. Preconcentration of Cd ", Pb ", Zn " and CvS were used for their preliminary determination by flame atomic absorption spectroscopy. The optimum pH values for quantitative soi ption ai e 5.8, 6.2, 6.5, 7.0 for Pb, Cu, Cd and Zn, respectively. The sorption ability of SN-SiO, to metal ions decrease in line Pb>Cu> >Zn>Cd. The soi ption capacity of the sorbent is 2.7,7.19,11.12,28.49 mg-g Hor Cd, Zn, Pb, andCu, respectively. The sorbent distribution coefficient calculated from soi ption isotherms was 10 ml-g for studied cations. All these metal ions can be desorbed with 5 ml of O.lmole-k HCl (sorbent recovery average out 96-100%). 

FAAS Flame atomic absorption spectroscopy the flame atomizes metals in solutions. Once in the gas phase, the atoms absorb UV-vis light, exciting electrons to higher energy levels. The amount of light absorbed is used to determine the metal concentration. 

The earliest work reported in this field was by Burguera et al. [103], who applied a flow injection system for on-line decomposition of samples and determined metals (Cu, Fe, Zn) by flame atomic absorption spectroscopy (F-AAS). The methodology involved the synchronous merging of reagent and sample, followed by decomposition of serum, blood, or plasma in a Pyrex coil located inside the microwave oven. This approach permits essentially continuous sample decomposition, drastically reduces sample processing time, and is suitable for those samples that require mild decomposition conditions (especially liquids). 

Maintaining the quality of food is a far more complex problem than the quality assurance of non-food products. Analytical methods are an indispensable monitoring tool for controlling levels of substances essential for health and also of toxic substances, including heavy metals. The usual techniques for detecting elements in food are flame atomic absorption spectroscopy (FAAS), graphite furnace atomic absorption spectrometry (GF AAS), hydride generation atomic absorption spectrometry (HG AAS), cold vapour atomic absorption spectrometry (CV AAS), inductively coupled plasma atomic emission spectrometry (ICP AES), inductively coupled plasma mass spectrometry (ICP MS) and neutron activation analysis (NAA). 

Olsen et al. (48, 20) have described an interesting method for the determination of lead in polluted seawater using FIA and flame atomic absorption spectroscopy. The system incorporates a Chelex-100 column for on-line preconcentration of the sample. The preconcentration and elution step improves the detection limit for lead by a factor of four (50 nM). Further increases in sensitivity are easily possible. The combination of this preconcentration step with a more sensitive detector, such as anodic stripping voltammetry, may make possible the determination of trace metals in seawater on a routine basis. 

Example 5.1 Total Metal Analysis of Soil, followed by Flame Atomic Absorption Spectroscopy... 

Figure 5.27 Typical results obtained for the total metal analysis of soil using flame atomic absorption spectroscopy. Digestion procedures , aqua regia 0, US EPA Method 3050B , US EPA Method 3050B (optional) [32] (cf. DQ 5.9).

Example 5.2 Total Metal Analysis of Soil Using X-Ray Fluorescence Spectroscopy - Comparison with Acid Digestion (Method 3050B), followed by Flame Atomic Absorption Spectroscopy... 

Figure 5.29 Sequential extraction results obtained for (a) Soil A , and (b) Soil CONTEST 32.3A , Step 1 , Step 2 S, Step 3 , residual fraction. Comparisons of the sequential extraction/flame atomic absorption spectroscopy (FAAS) total metal analysis and acid digestion/FAAS approaches for (c) Soil A , and (d) Soil CONTEST 32.3A , sequential total S, FAAS total [32] (cf. DQ 5.11).

Most other metals present in pharmaceuticals are present in sufficient concentrations that high sensitivity is not imperative and they may therefore be determined by flame atomic absorption spectroscopy. These products are extremely variable in composition but nonetheless yield easily to this type of analysis, which is generally unaffected by compounding agents such as binders or expanders. Thus, the elements Na, K, Mg, Ca, Mn, Fe, Co, Cu, Zn, and Mo are among those determinable by flame (51-53) and, recently, furnace (54) atomic absorption in multivitamin-mineral tablets. Chemical interactions between some metals dictate the use of an internal standard when several elements are present simultaneously. It should be noted here that a spark emission or ICP spectrometer equipped with an appropriate polychromator would have the advantage of simultaneous and therefore more rapid analysis in these multielemental products. These techniques have probably not been fully utilized in this regard. 

Flame atomic absorption spectroscopy (AAS) is a specialized spectroscopic technique widely used in analytical laboratories to find the levels of trace metals in solution. By consulting a textbook on analytical chemistry, find out (i) what light sources are used in AAS and (ii) the purpose of the flame. 

Flame Atomic Absorption Spectroscopy (FAAS) >1.0 Any matrix Perkin-Elmer (1982) Not sensitive enough for biomonitoring wifiiout extensive sanqile digestion, metal chelation and organic solvent extraction. 

Sebor, G., Long, L, Kolihova, D., Wasser, O., (1982) Effect of the type of organometallic iron and copper compounds on the determination of both metals in petroleum samples by flame atomic absorption spectroscopy. Analyst, 107,1350-1355. 

Analytical methods of atomic spectroscopy have been used in forestry and wood product research since their earliest development. Nowadays, almost all of the spectroscopic techniques available are employed in the analysis of metals and trace elements in diverse samples of industrial and environmental origin. The techniques that find most regular application include flame atomic absorption spectroscopy (F-AAS), graphite furnace atomic absorption spectroscopy (GF-AAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and, occasionally, also direct current plasma atomic emission spectroscopy (DCP-AES). In many applications F-AAS is a sufficiently sensitive and precise technique however, in the analysis of some environmental samples for trace elements (forest soils, plant material and water) where concentrations may be very low (of the order of 100 ng mL" ) the greater sensitivity of GF-AAS and ICP/DCP-AES is required. In considering the applications of atomic spectroscopy to forestry and... 

Atomic absorption spectrometry (AAS) has been used to determine cationic and anionic surfactants indirectly. Two methods have been put forward based on the formation of the ion pair between surfactant and hexanitrocobaltate (for cationic compounds) or bis(benzoyl)pyridine thiosemicarbazone cobalt (III) (for anionic compounds). In the former case, the complex is extracted with 1,3-dicloroethane and in the latter with an isopentylacetate and isopentyl alcohol mixture. Concentration of cobalt is determined in the organic phase using electrothermal atomic absorption spectroscopy (ETAAS), while for anionic surfactants, flame atomic absorption spectroscopy (FAAS) can also be used. Interferences like metal ions, anions and organic compounds do not have a great relevance. The two methods were applied to determine dodecyltrimethylammonium bromide in shampoos (Chattaraj and Das, 1992) and sodium lauryl sulfate (SDS) in toothpastes (Chattaraj and Das, 1994). 

Atomic absorption spectroscopy is more suited to samples where the number of metals is small, because it is essentially a single-element technique. The conventional air—acetylene flame is used for most metals however, elements that form refractory compounds, eg, Al, Si, V, etc, require the hotter nitrous oxide—acetylene flame. The use of a graphite furnace provides detection limits much lower than either of the flames. A cold-vapor-generation technique combined with atomic absorption is considered the most suitable method for mercury analysis (34). 

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. 

Essentially the same spectrometer as is used in atomic absorption spectroscopy can also be used to record atomic emission data, simply by omitting the hollow cathode lamp as the source of the radiation. The excited atoms in the flame will then radiate, rather than absorb, and the intensity of the emission is measured via the monochromator and the photomultiplier detector. At the temperature achieved in the flame, however, very few of the atoms are in the excited state ( 10% for Cs, 0.1% for Ca), so the sample atoms are not normally sufficiently excited to give adequate emission intensity, except for the alkali metals (which are often equally well determined by emission as by absorption). Nevertheless, it can be useful in cases where elements are required for which no lamp is available, although some elements exhibit virtually no emission characteristics at these temperatures. 

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. 

Investigation of atomic spectra yields atomic energy levels. An important chemical application of atomic spectroscopy is in elemental analysis. Atomic absorption spectroscopy and emission spectroscopy are used for rapid, accurate quantitative analysis of most metals and some nonmetals, and have replaced the older, wet methods of analysis in many applications. One compares the intensity of a spectral line of the element being analyzed with a standard line of known intensity. In atomic absorption spectroscopy, a flame is used to vaporize the sample in emission spectroscopy, one passes a powerful electric discharge through the sample or uses a flame to produce the spectrum. Atomic spectroscopy is used clinically in the determination of Ca, Mg, K, Na, and Pb in blood samples. For details, see Robinson. 

Atomic Absorption Spectroscopy. One of the more sensitive instruments used to detect metal-containing toxicants is the AA spectrophotometer. Samples are vaporized either by aspiration into an acetylene flame or by carbon rod atomization in a graphite cup or tube (flameless AA). The atomic vapor formed contains free atoms of an element in their ground state, and when illuminated by a light source that radiates light of a... 

In 1952, Walsh in Australia realized the inherent advantages of atomic absorption spectroscopy over methods based on flame emission for quantitative analysis, and he has given a personal account of the development of the technique.197 Walsh s death in 1998 resulted in a memorial issue of the journal Spectrochimica Acta (B). As well as a brief biography of Walsh and a list of his publications, this contained 22 papers on all aspects of the history of atomic absorption spectroscopy. Together they constitute a valuable record of the birth of this important technique, the difficulties of bringing satisfactory instruments to market, and the history of the application of the method to quantify metals in a wide variety of materials and environments.198... 

Atomic spectroscopy is a quantitative technique used for the determination of metals in samples. Atomic spectroscopy is characterized by two main techniques atomic absorption spectroscopy and atomic emission spectroscopy. Atomic absorption spectroscopy (AAS) is normally carried out with a flame (FAAS), although other devices can be used. Atomic emission spectroscopy (AES) is typified by the use of a flame photometer (p. 168) or an inductively coupled plasma. The flame photometer is normally used for elements in groups I and II of the Periodic Table only, i.e. alkali and alkali earth metals. 

When new analytical tools become available, more often than not considerations of responsibility to the patient, practicality, and economy will keep the clinical chemist from accepting such newly developed techniques without careful deliberation. It appears that presently atomic abso tion spectroscopy is slowly finding entrance into medical research and service laboratories, and there is reason to expect that this technique will find wider use and greater application than emission flame spectroscopy. Virtually all metals, with very few exceptions, can be determined by atomic absorption spectroscopy. It is anticipated that this technique not only will replace currently used analytical methods for metals, but will also make feasible the routine determination of elements now impractical by conventional means. Furthermore, the operational stability of available instruments and the simplicity of actual performance of measiurements make this technique well suited for automation, by addition of an automatic sample feed and automatic recording. 

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