Development and optimization of a digestion method for heavy metal determination in scleractinian corals by Atomic Absorption Spectrometry (AAS).

Abstract

In the last decade a great number of studies have been directed especially to the evaluation of the environmental impact of heavy metal concentration levels in coral barriers. Related to studies in scleractinian corals, many chemical techniques have been proposed to determine heavy metals but Atomic Absorption Spectrometry (AAS) is the most widely used; however, regarding sample pretreatment methods there is not a unique criterion on the requirements to obtain the precise and accurate results needed in this analysis. So, in this paper the application of several widely used pretreatment methods for digestion of corals and sediments were studied in which HNO₃, HCl and HClO₄ are used in different conditions (concentration, temperature, etc.), with the aim of comparing their efficiency. The method in which a combination of HNO₃ and HClO₄ was used resulted the most effective one. A 2² experimental design was carried out to study the influence of the HNO₃ volume as well as to optimize the HNO₃:HClO₄ mixture. Finally the method was validated using reference certificate material (SOIL-7) using the NIST accuracy test and applying it in the analyses of different coral samples which produced results with appropriate analytical quality.