Analytical proposal for trace element determination in human hair. Application to the Biscay province population, northern Spain

The proposed methodology was applied to 114 donors aged 0–90years old from various geographical areas of the Biscay province (northern Spain) which were characterized by differing environmental conditions and dietary habits. 22 trace elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Sr, Ti, V and Zn) were determined by inductively coupled plasma techniques (ICP) with mass spectrometry (MS) and optical emission (OES) detections. Analytical steps were deeply discussed including pre-treatment (washing) and acid treatment (microwave system). Additionally, the pre-treated and non pre-treated human hair samples were studied by scanning electron microscope coupled to an energy dispersive X-ray spectrometer (SEM–EDX). This microscale characterization was found essential to assess the proposed human hair washing step prior to the analytical determinations.