Analysis by atomic absorption spectrometry

NH3 is used (with an inline-filter), it should first be bubbled through an ammoniacal solution of EDTA ca. 0.01 mol/L) to reduce copper and nickel impurities before passing into distilled water. Alternatively, gaseous NH3 may be obtained from a 25 % ammonia solution (a.g.) by heating. 

Solvents. Organic solvents such as Freon or chloroform, employed to extract and pre-concentrate trace elements from seawater solutions are commonly purified by smooth distillation in vitreous silica stills or better by sub-boiling distillation in quartz stills. Chloroform of reagent grade quality is best cleaned by first extracting with the purest available 2 mol/L HCl (to reduce the inorganic salt content) and subsequent distillation. 

The use of carefully cleaned reagents is essential for low laboratory or method blanks (see section on Qualitiy control in Chapter 1). In order to prove whether or not the laboratory analysis is correct, certified reference materials (CRMs) have been developed. The values certified for certain elements (with specified uncertainties) are commonly based on the results of analyses by at least two reliable independent methods. 

Suitable reference material should match matrix composition and analyte concentration of the unknown samples as close as possible. Of the relatively large number of suppliers only very few offer reference materials for trace analysis in seawater (see Howard and Sta-tham, 1993). Such material collected in the off-shore North Atlantic mixed layer (NASS) and Nova Scotia estuarine (SLEW) and nearshore coastal waters (CASS) respectively, is available from the National Research Council of Canada (Ottawa, Canada KIA OR6). These samples have been certified for 13 elements (As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni, U, Se, Zn). 

Analyses of certified reference samples are not only a great help in assessing the precision and accuracy of a newly developed analytical procedure, but such measurements also are essential for quality control programmemes in routine measurements (see Chapter 1). It should be emphasized, however, that accurate analyses of reference materials do not necessarily indicate accuracte results for collected field samples. If analytes have been lost, or were added through contamination during sampling, this bias will not be monitored, of course, by the use of CRMs. 

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Asplla, K. I., Chakrabartl, C. L., and Bratzel, M. P., Jr. "Pyrolytic Graphite-Tube Micro-Furnace for Trace Analysis by Atomic Absorption Spectrometry". Anal. Chem. (1972),... 

Pellenberg and Church [58] have discussed the storage and processing of estuarine water samples for analysis by atomic absorption spectrometry. 

Monien and Stangel [598] studied the performance of a number of alternative chelating agents for vanadium, and their effect on vanadium analysis, by atomic absorption spectrometry with volatilisation in a graphite furnace. Two promising compounds were evaluated in detail, namely 4-(2-pyridylazo) resorcinol in conjunction with tetraphenylarsonium chloride and tetramethylenedithiocar-bamate. These substances, dissolved in chloroform, were used for extraction... 

Zhuang et al. [664] used palladium salts as a coprecipitation carrier for the concentration of cadmium, cobalt, and lead in seawater prior to analysis by atomic absorption spectrometry. 

Workers at the Department of the Environment, UK [47], have described a procedure for the determination of methylmercury compounds in soils and sediments which involves extraction with a carbon tetrachloride solution of dithizone, reduction to elemental mercury then analysis by atomic absorption spectrometry. 

Bettembourg, J. M., Blue Glasses of Stained-Glass Windows. Analysis by Atomic Absorption Spectrometry, Int. Congr. Glass, Artistic Hist. Commun., 9th, 1971 (1972) 225-239 (French). 

It is clear then that the chemical flame is an effective means by which a free, neutral atom population may be produced from a sample solution for analysis by atomic absorption spectrometry. The fact that flames were inherited from the older technique of flame emission spectrometry may account in part for their popularity, although they also have the following advantages for use in AAS ... 

The differentiation of inorganic As(III) and As(V) can be achieved by exploitation of the pH sensitivity of the reduction of arsenic compounds by sodium borohydride, as adapted to analysis by atomic absorption spectrometry . An alternative to pH control of arsine production involves suppression of As(V) reduction by the addition of DMF . 

Yanagisawa, M., Suzuki, H., Kitagawa, K. and Tsuge, S. (1983) Separative column atomizer (SCA) for direct analysis by atomic absorption spectrometry. GC separation caracteristics. Spectrochim. Acta, 38B, 1143-1149. 

The nearest sites from which stream sediments were collected for analysis by atomic absorption spectrometry are two streams near Chapada dos Guimariies, for which data on the content of various metals, are reported in Table IV The water chemistry of these streams, especially the conductivity and water hardness, is similar in that in the headwaters of the Rio das Mortes. Due to differences in the methods of collection and fractionation of the sediment samples by different researchers, much of the data in the literature are not strictly comparable. Nevertheless, from various data compiled by Petr and Irion (P), it is evident that the amounts of most metals in these samples are much less than those in the clay fraction of river sediments in many parts of the world. Unfortunately, these authors provided no comparative data for iron, which was present in rather large amounts in the Chapada sediment samples. Especially notable is the very small amount of calcuim present, which accounts for the undetectable water hardness. The Ca content of the clay fraction of the sediment in various rivers of the world is 90 to... 

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