Arsenic determination ETAAS

Gaseous and volatilised analytes can also be easily determined by FAAS and ETAAS. For example, the determination of several elements by the formation of covalent volatile hydrides e.g. arsenic, selenium) and cold vapour generation (mercury and cadmium) is feasible with good analytical sensitivity (see Section 1.4.1.1). 

A systematic difference was observed between high chromium values obtained by NAA techniques and ICP-MS and ICP-AES data. It was suspected that in some cases the digestion method used was not sufficiently strong to decompose the matrix the addition of HF after HNO3 decomposition is a prerequisite. The main problem was, however, related to strong interferences occurring at mass 52 with argon. As already mentioned for arsenic, ICP-MS and ICP-AES were not considered to be suitable for certification and the different sets were consequently withdrawn ETAAS is clearly more reliable for chromium determination in comparison to ICP-MS. 

Sperling et al.[4] determined arsenic(lll) and total arsenic in sea and lake waters by ETAAS, following on-line reduction and preconcentration of the DDC complex using a micro-colunm packed with C g sorbent, using a manifold modified on the basis of that shown in Fig. 4.11. A mixture of sodium sulphite, hydrochloric acid, sodium thio-sulphate and potassium iodide was used to achieve fast reduction of arsenic(V) to arsenic(IIl), and ethanol was used to elute the sorbed arsenic-DDC complex. The detection limits for As(ni) and As(ID+V) were 0.11 and 0.15 pg 1 respectively. 

The developed flow system was applied to the determination of the inorganic species of arsenic in groundwater samples originating from Tierra de Pinares (Segovia, Spain) as described in the Experimental section. Five replicate determinations of both total As and As(III) were carried out on each sample by the standard additions method. Results are displayed in Table 7. Total As was also determined in samples by electrothermal atomic absorption spectrometry (ETAAS) for comparison. 

Table 7. Contents (mean, n=5) of As(III), As(V) and total As, determined in groundwater samples by the proposed SI-ASV system, and comparison between total arsenic concentrations determined by SI-ASV and ETAAS. Concentration units, pg H.

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