Analytical flameless atomic absorption

Analytical Response In Flameless Atomic Absorption Spectrometry". Anal. Chem. (1973), 1812-1816. 

Millward and Bihan [59] studied the effect of humic material on the determination of mercury by flameless atomic absorption spectrometry. In both fresh and seawater, association between inorganic and organic entities takes place within 90 min at pH values of 7 or above, and the organically bound mercury was not detected by an analytical method designed for inorganic mercury. The amount of detectable mercury was related to the amount of humic material added to the solutions. However, total mercury could be measured after exposure to ultraviolet radiation under strongly acid conditions. 

Results(79) from a Round Robin analyses for the lead content of air particulate filters were given along with the average values obtained from 65 laboratories participating in the study. The procedures used by the other laboratories included x-ray, FAA, flameless atomic absorption, emission spectrometric, and dithizone-spectropho-tometric. The overall analytical agreement was very good. 

Trace levels (10 to 10 g/g of sample) of silver can be accurately determined in biological samples by several different analytical techniques, provided that the analyst is well acquainted with the specific problems associated with the chosen method. These methods include high frequency plasma torch-atomic emission spectroscopy (HFP-AES), neutron activation analysis (NAA), graphite furnace (flameless) atomic absorption spectroscopy (GFAAS), flame atomic absorption spectroscopy (FAAS), and micro-cup atomic absorption spectroscopy (MCAAS). 

Table III shows that two quite different analytical techniques, Flameless Atomic Absorption Spectroscopy and Neutron Activation Analysis, yield equivalent frequencies of detection of firearms discharge residue.

The immediate source of nutrient elements for plants is the soil solution but there is a paucity of information concerning its composition especially for micronutrients. A number of practical problems arise in studying the soil solution and the first is actually getting a sample of it. The soil solution can be removed for analysis by centrifugation or direct suction. Some workers prefer a saturation extract , when the soil is allowed to equilibrate with water which is then extracted by mild suction. The solutions extracted by these techniques are very dilute and consequently not stable chemically. They present considerable analytical problems although these have eased in recent years now that very sensitive flameless atomic absorption methods have become widely available. 

Many alternative techniques, both qualitative and quantitative, have been investigated either for screening purposes or as primary methods. Such techniques include atomic absorption spectrophotometry, molecular luminescence, electron spin resonance spectrometry, X-ray analysis methods, and electro analytical methods. Flameless atomic absorption spectrophotometry (FAAS) is the technique that has almost completely replaced NAA. 

In flameless atomic absorption the analyte often tends to react with the graphite furnace or rod to form carbides. In such cases atomisation is suppressed. Release agents are used to react preferentially with the graphite releasing the analyte on atomisation. An application of this is in the determination of aluminium, barium, beryllium, silicon and tin. A large enhancement of the signal has been observed [47] when calcium (as the nitrate) is added to the analytical solutions. This has been suggested as due to a reduction in the formation of carbide in the presence of calcium. A calcium level of 1000 to 2000 mg l-1 in the solutions has been reported as the optimum in most cases. 

The Element.—Analytical methods for the determination of trace quantities of selenium in two very different materials have been described. The first275 employs the use of flameless atomic absorption spectrophotometry for the direct determination of selenium (and Pb, Bi, Se, Te, and Tl) at p.p.m. levels in high-temperature alloys. The second method276 is able to determine the selenium content of plant material at levels as low as 0.005 fxg g The method involves the reaction of SeIV with 4-nitro-o-phenylenediamine to form 5-nitropiaselenol, which may be detected by means of a gas chromatograph. 

The first requirement can be easily fulfilled by the preconcentration of the analyte before the analysis. Preconcentration has been applied to sample preparation for flame atomic absorption (25) and, more recently, for ICP (79,80) spectroscopy. However, preconcentration is not completely satisfactory, because of the increased analysis time (which may be critical in clinical analysis) and the increased chance of contamination or sample loss. Most important, however, a larger initial sample size is necessary. The apparent solution is a more sensitive technique. Table 2 lists concentrations of various metals in whole blood or serum (81,82) in comparison to limits of detection for the various atomic spectroscopy techniques. In many cases, especially for the toxic heavy metals, only flameless atomic absorption using a graphite furnace can provide the necessary sensitivity and accommodate a sample of only a few microliters (Table 1). The determination of therapeutic gold in urine and serum (83,84), chromium in serum (85), skin (86) and liver (87), copper in semen (88), arsenic in urine (89), manganese in animal tissues (90), and lead in blood (91) are but a few examples in analyses which have utilized the flameless atomic absorption technique. 

The determination of mercury in hair by flameless atomic absorption spectroscopy (Association of Official Analytical Chemists, International, Method 971.21, 16th ed., modified for hair)... 

Chikuma M., Aoki H., Tanaka H. Determination of metal ions in environmental waters by flameless atomic absorption spectrometry combined with preconcentration using a sulfonated dithizone-loaded resin. Analytical Sciences 1991 7 1131-1134. 

Recommended Air Volume 960 L Recommended Sampling Rate 2.0 L/min Analytical Procedure Air filter samples are digested with nitric acid. After digestion, a small amount of hydrochloric acid is added. The samples are then diluted to volume with deionized water and analyzed by either flame atomic absorption spectroscopy (AAS) or flameless atomic absorption spectroscopy using a heated graphite furnace atomizer (AAS-HGA). 

The most common analytical methods that can sensitively measure manganese include neutron activation analysis, X-ray fluorescence, proton-induced X-ray emission, inductively coupled plasma emission, EPR, and flameless atomic absorption spectrophotometry (AAS). Currently, the most common method employed is flameless AAS. All of these methods, with the exception of EPR, measure the total concentration of manganese in the samples. EPR allows selective measurement of bound versus free manganese. 

Nickel and vanadium along with iron and sodium (from the brine) are the major metallic constituents of crude oil. These metals can be determined by atomic absorption spectrophotometric methods (ASTM D-5863, IP 285, IP 288, IP 465), wavelength-dispersive X-ray fluorescence spectrometry (IP 433), and inductively coupled plasma emission spectrometry (ICPES). Several other analytical methods are available for the routine determination of trace elements in crude oU, some of which allow direct aspiration of the samples (diluted in a solvent) instead of time-consuming sample preparation procedures such as wet ashing (acid decomposition) or flame or dry ashing (removal of volatile/combustible constituents) (ASTM D-5863). Among the techniques used for trace element determinations are conductivity (IP 265), flameless and flame atomic absorption (AA) spectropho-... 

Iron concentrations in extracts were measured in triplicates with a Hitachi-Z8100 atomic absorption spectrophotometer equipped with a Zeeman correction system. The flame atomizer was used for extracts from total digestions and acid extractions the flameless graphite furnace was used for extracts of sulfidic iron. The contents of iron from sequential extractions were corrected for water contents (but not for salt contents) in sediments in order to get concentrations on a dry weight basis. Accuracy and precision for Fe analysis were checked by replicate extraction analysis (n = 5) of standard reference material BCSS-1, which is issued by the National Research Council, Canada and has a certified iron content of 3.287 0.098% our analytical value was 3.266 0.056%, indicating good accuracy of our analyses. The relative precision for iron determination in this study is better than 5%. 

The approved reference method for enforcement purposes (CFR, 1982, 40 58) uses hi-vol samplers and measures lead by atomic absorption spectrometry (AAS). This laboratory method, which has been available in various analytical configurations for several decades, has been shown to be particularly reliable and sensitive for measuring lead quantitatively in a large range of environmental media. Flameless AAS is a more sensitive variation of this technique than conventional flame methods and has been the choice for many years. As with any lead measurement method, sample handling must minimize both contamination with lead and loss of lead from the sample. Comparatively, the contamination problem is still the more problematic and this is certainly the case for analyses in U.S. urban areas and in other industrialized nations (NAS/NRC, 1993 Patterson, 1983 Settle and Patterson, 1980). For air sample analyses, the codified reference method using AAS is quite adequate for a wide range of air lead concentrations. 

---