Determination of Heavy Metal Contamination

An important analysis regarding toxicological and legal requirements of flavourings is the control of heavy metal contaminations. Most of the heavy metals show toxic effects in humans, even in trace quantities. Their determination can only be accomplished using trace analysis techniques. In practice, the different analytical techniques Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) have been employed successfully. Both methods require complete dissolution of the sample by decomposition. 

The most common method is the AAS. This method offers a high selectivity, low detection limits and the possibility to detect a wide range of heavy metals. For different elements this method requires the use of some technical variants  

This technique is useful for determination of e.g. Ag, Ni, Cd, Cr, Zn, Cu, Pb, Co, Fe, Mn, at concentration ranges of 50 pg/1. The sample solution is sprayed as aerosol in the approx. 2300°C hot acetylene flame. The measurable absorption at the elements specific fixed wavelength is proportional to the requested quantity [2]. 

With this method heavy metals are atomized electrothermally. The detection limits are about 100-times lower than those for the Flame-AAS. Problems with interference signals at this very low measuring range (below lp/1) can be overcome by using the Zeemaim correction technique [2]. 

The Cold-Vapour technique is required for determination of mercury because mercury is insensitive to the other AAS techniques. This method utilizes the unique characteristic of mercury to exist in the atomic form at room temperature. This method can only be used for determination of mercury because of unspecific interferences for other elements [2], 

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