Al determination in whole blood samples as AlF via high-resolution continuum source graphite furnace molecular absorption spectrometry: potential application to forensic diagnosis of drowning

Abstract

In this work, a new methodology for direct determination of Al in whole blood samples by means of high-resolution continuum source graphite furnace molecular absorption spectrometry has been developed, based on the formation of the AlF diatomic molecule in the graphite furnace and the subsequent monitoring of its molecular absorption. The proposed methodology provides an alternative method to conventional atomic absorption, solving most of the problems related to the latter technique, particularly matrix effects, providing a straightforward alternative for blood analysis. The addition of NH₄F·HF, which is required for promotion of the AlF molecule, was found to improve sample matrix removal for whole blood samples, whether they contain EDTA or heparin as anticoagulant agents. Besides minimizing residues in the graphite platform, this circumstance enabled the use of aqueous standards to build a calibration curve, avoiding the need for the cumbersome method of standard additions, while not affecting significantly detection capabilities (1.8 μg L⁻¹ LOD). The method developed was also used for exploring the possibilities of Al as a chemical marker assisting forensic diagnosis of death-by-drowning. For this purpose, a set of samples (water and blood) obtained from 8 drowning suspects and two controls were analysed for their Al levels. Although additional studies with a large number of samples would be needed in order to draw definitive conclusions from a forensic point of view, a positive correlation between Al concentration in the drowning water and Al concentration in the blood of drowning suspects was found, supporting the validity of Al as a marker for drowning diagnosis.