On-line preconcentration of nickel by carbonyl vaporization with flow injection and continuous flow systems in combination with sensitive determination by electrothermal atomic absorption spectrometry

A method is described for the detection of nickel in biological matrices, at very low concentrations and without major interferences. The on-line system involved the coupling of a flow system (continuous flow and flow injection) with transversely heated electrothermal atomic absorption spectrometry (ETAAS). Nickel was volatilized as nickel tetracarbonyl and trapped on a graphite surface. Carbonyl generation was optimized using a simple carbon monoxide generator together with sodium tetrahydroborate(III) as reagent for the formation of pure metallic nickel. The characteristic concentration was 0.13 ug per litre for an absorption of 0.0044 and the detection limit was 0.18 ug per litre (500 ul sample volume). Detection limits below 0.01 ug per litre were possible in the continuous mode. This method was not free from interferences but systematic errors were eliminated by use of the standard additions method. The method was validated by analysis of standard and certified reference materials, NIST SRM 1643c (water) and BCR CRM 281 (rye grass). Levels of nickel were in good agreement with certified values.