Cadmium determination ETAAS

Work Item B determination of mercury by CVAAS after pressure digestion. Work Item C determination of lead and cadmium by ETAAS after dry ashing. Work Item D performance criteria and general considerations. 

Work Item H determination of lead and cadmium by ETAAS after microwave digestion. 

As to the analysis of trace elements in paper, cardboard and raw materials for the production of paper, high concentration elements such as Cu, Fe or Ti can easily be determined by FAAS Cd and Pb are frequently analysed by GFAAS. Cadmium in pulp and paper was determined by AAS after pressurised digestion with nitric acid [145]. An interlaboratory comparison of Cd in wrapping paper was reported, mainly based on pressure digestion in FIFE bombs with sub-boiled nitric acid, followed by ETAAS [59]. For wrapping paper used for foodstuffs, next to the total content of toxic heavy metals, the soluble or leachable fraction is of particular interest. 

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). 

Work Item F determination of lead, cadmium, chromium and molybdenum by ETAAS after pressure digestion. 

Human activities often mobilize and redistribute natural compounds in the environment to an extent that they can cause adverse effects. Much attention has been paid to the determination of trace of pollutant elements on account of their significant effect on the environment. The potential of USAL has been put into use in environmental element analysis. Thus, the US leaching of cadmium from coals and pyrolysed oil shale prior to ETAAS [56] resulted in a twofold increase in precision, better detection limits and decreased background absorbance in relation to total digestion. Cadmium has also been successfully leached with US assistance from ash samples with subsequent flow-injection coid-vapour atomic absorption spectrometry [57]. Additional examples include the leaching of germanium from soiis with an uitrasonic probe in 10 min [58] or that of lead from coal in 60 s [59]. 

Table 8.22 presents the results of the comparison of different methods used in this certification. The CVs within one method are generally of the same order of magnitude as the CVs between different techniques. For ICPMS (cadmium), ETAAS (nickel) and FAAS (zinc) the larger CVs are due to operating close to the limits of determination ... 

Cadmium. In the first two steps, FAAS was not considered to be a suitable technique for the determination of the low Cd content and the corresponding sets were consequently withdrawn. Some ETAAS results were below determination limits and were therefore rejected. Conclusions could hardly be drawn on the basis of the three remaining results, except that the extractable Cd content was too low for the purpose of testing the extraction scheme for both steps 1 and 2. 

Despite the improved sensitivity of the flame AAS methods with on-line column preconcentration, the detection limits achieved are still insufficient for most unpolluted water samples. Cadmium in such samples (CASS-1, CASS-2, NASS-2, SLRS-1, etc.) have been successfully determined using an ETAAS system with on-line sorbent extraction preconcentration similar to the one described in Sec. 8.8.3. A detection limit of 0.0008 /ig 1 Cd was achieved with almost complete removal of the interfering matrix of sea water samples [10]. 

Porta et al.(ll] silso developed an on-line column preconcentration method for the determination of cadmium and other trace metals (Pb, Cu, Ni, and Fe) in Antarctic sea water using ETAAS. A detection limit of 0.(KX)4 /ig 1 was achieved for cadmium. The APDC complexes of the trace metals were collected on a micro column packed with C 8< XAD-7 or XAD-2 sorbent and acetonitrile was used for elution. According to the authors, the main drawback of the method is at least two successive 80 //I elutions (with an intermediate evaporation in the furnace) are necessary to recover all the analytes from the column. 

The dual-column and single-column ion-exchange precoilcentration flame AAS systems as well as the DDC-Cis sorbent extraction flame AAS and ETAAS systems used for the determination of cadmium were also used for the determination of copper in water samples. The detection limit for the dual-column system was 0.07-0.09 /ig l at 60 samples h [7] for the sorbent extraction preconcentration flame AAS system, 0.2 /xg r at 120 samples h [9] for the sorbent extraction ETAAS system, 0.02 /xg 1 at approximately 20 samples h [10]. The sensitivity of sorption column preconcentration methods with flame AAS detection should be sufficient for the determination of copper in most natural water samples. 

Fang and Dong [3] determined cadmium in whole blood digests by ETAAS with on-line coprecipitation-dissolution also using the Fe(II)-HMDTC system, achieving a detection limit of 0.003 /ig 1 ... 

Fang and Dong [3] determined nickel in whole blood digest by ETAAS following on-line coprecipitation-dissolution using the same filterless system as for cadmium. A detection limit of 0.02 pg 1 was reached, making it possible to determine nickel in the blood of unexposed persons. 

The sensitivity of flame AAS is insufficient for the determination of cadmium in urine at nonnal levels. ETAAS methods require sample digestion and/or chemical modification of the sample matrix, resulting in complicated procedures. In this procedure, cadmium is determined efficiently by flame AAS in undigested urine following an on-line separation of the matrix and preconcentration of the analyte using a micro-column packed with CPG- 8HQ ion-exchanger (quinolin-8-ol immobilized on porous glass). 

The most common analytical procedures for measuring cadmium concentrations in biological samples use the methods of atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES). Methods of AAS commonly used for cadmium measurement are flame atomic absorption spectroscopy (FAAS) and graphite furnace (or electrothermal) atomic absorption spectroscopy (GFAAS or ETAAS). A method for the direct determination of cadmium in solid biological matrices by slurry sampling ETAAS has been described (Taylor et al., 2000). 

Fang and Dong [60] adapted the online coprecipitation preconcentration for ETAAS. They determined cadmium and nickel in digested whole blood. Enrichment factors of 16 and 8 were obtained for cadmium and nickel, respectively, using 20- and 40-sec precipitate collection times at a flow rate of 3 mL/min for cadmium and 2 mL/min for nickel. The detection limits were 0.003 p,g/liter for cadmium and 0.02 ng/liter for nickel. 

O. Acar. Determination of cadmium, copper and lead in soils, sediments and sea water samples by ETAAS using a Sc + Pd + NH4NO3 chemical modifier. Talanta 65 672-677, 2005. 

M. B. Dessuy, Multivariate optimisation and validation of an analytical method for the determination of cadmium in wines employing ETAAS, /. Brazil. Chem. Soc., 2009, 20(4), 788-794. 

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