The use of surfactants to obtain cadmium atoms at room temperature and its application for the cold vapour AAS determination of the metal

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Abstract
So far, mercury is the only metal that has been proved to be able to form a monoatomic vapour at room temperature. This property has been widely used in analytical techniques, particularly in atomic spectroscopy, where cold vapour atomic absorption spectrometry (CV–AAS) has become the most common method for the determination of low levels of Hg. In this communication we will show evidence that cadmium appears also to be able to form ‘cold atomic vapour’ in appropriate conditions. Experimental results show that by reduction of Cd2+ with sodium tetrahydroborate in vesicles of didodecyldimethylammonium bromide (DDAB), some volatile cadmium species (probably hydrides) can be produced that transport the metal to the atomic absorption measurement cell, where atomic cadmium vapour has been proved to be present in measurable concentrations. Based on these facts, a new determination of traces of cadmium by cold vapour atomic absorption spectrometry is proposed. Such CV–AAS determination of the metal is very sensitive in normal conditions (detection limit of 0.08 ng ml–1) and the sensitivity can be improved further by working at lower temperatures for generation of the volatile species.