Sensitivity GFAAS

GFAAS has many advantages over FA AS, such as fast and complete atomisation of the sample (almost 100% of the sample is atomised as opposed to 0.1 % in FAAS), low cost, the fact that the sample is easy to remove after analysis and, most importantly, that it gives 2-3 orders of magnitude better sensitivity. GFAAS is normally used in conjunction with an autosampler. Recent developments in GFAAS have been described elsewhere. ... 

At copper concentrations below 5 /precision data in Figure 1 became just acceptable, the more sensitive GFAAS can be used with advantage. For instance Carelli et al. (1982) reported an RSD better than 3% for copper in urine down to 0.2 /sample throughput of FAAS is more attractive than the slow rates encountered with GFAAS methods. 

Sample preparation for the determination of trace concentration levels of the many priority pollutant metals is strongly connected to the nature of the determinative technique. Historically, FIAA was first used to measure metals. The more sensitive GFAA technique followed. Along about the same time as GFAA was being developed, ICP-AES came along. ICP-AES afforded the opportunity to measure more than one metal in a sample at a time, the so-called multielement approach. In recent years, the development of ICP-MS has carried trace metal analysis to significantly lower IDEs and introduced the opportunity to identify and to quantitate the various elemental isotopes. 

In industrial research laboratories, AAS (in particular FAAS) is no longer being used to the same extent as in the past, despite the aforementioned important improvements in AAS technology. More rapid, multi-element methods have gradually taken over, such as ICP-AES, ICP-MS and NAA. However, the determination of one element is faster with AAS than with an ICP technique. Also, ICP-AES does not supersede GFAAS in terms of sensitivity and selectivity. 

The primary methods of analyzing for lead in environmental samples are AAS, GFAAS, ASV, ICP/AES, and XRFS (Lima et al. 1995). Less commonly employed techniques include ICP/MS, gas chromato-graphy/photoionization detector (GC/PID), IDMS, DPASV, electron probe X-ray microanalysis (EPXMA), and laser microprobe mass analysis (LAMMA). The use of ICP/MS will become more routine in the future because of the sensitivity and specificity of the technique. ICP/MS is generally 3 orders of magnitude more sensitive than ICP/AES (Al-Rashdan et al. 1991). Chromatography (GC,... 

DeJonghe et al. 1981 NIOSH 1978b). GFAAS detection is more sensitive than PID, but both have good accuracy. 

A combination of hydride generation with GFAAS was proposed for signal enhancement, instead of flame AAS. It was found that older tubes had better sensitivity than new ones31. 

Flame atomic absorption spectrometry (FAAS) can be used to detect most elements present at levels greater than about 100 pg 1 . For more sensitive determinations graphite furnace atomic absorption spectrometry (GFAAS) is the technique of choice. In addition, if the volume of the fraction is limited GFAAS is ideally suited for the determination because only a few microfitres (5-20 pi) of sample... 

In some cases, it is essential to use a sensitive technique like GFAAS in order to measure the level of contamination in the reagents used. This is important because the presence of extraneous contamination may lead to the formation of artifacts or the amount of element associated with particular species (those that can incorporate the analyte in-vitro) may be overestimated. 

GFAAS technique is more sensitive than FAAS methodology for determination of silver in water samples. Rain and stream water have been analyzed by GFAAS technique to detect silver at ng/mL levels (Rattonetti 1974). 

The formed free atoms absorb the light at a characteristic wavelength from a hollow cathode lamp that is positioned on one side of the flame. A spectrophotometer with a grating monochromator located on the other side of the flame measures the intensity of the light beam. Because absorption is proportional to the number of free atoms that are produced in the flame, the light energy absorbed by the flame is a measure of the element s concentration. The FLAA technique is relatively free of interelement spectral interferences, but it has the sensitivity that is inferior to ICP-AES or GFAA. 

GFAAS has also been used for measuring trace levels of vanadium in the serum and urine of humans and animals (Ishida et al. 1989 Mousty et al. 1984). Detection limits of 0.08 ag/L in serum and 0.06 ag/L in urine were achieved (Ishida et al. 1989). The GFAAS technique is as sensitive as NAA, and is also rapid, simple, relatively free from interference, and relatively inexpensive (Ishida et al. 1989 Krishnan et al. 1976). 

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