“…Among these, atomic spectroscopic methods, such as atomic absorption spectrometry (AAS) [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] with flame [ 16 , 19 , 20 ] or electrothermal atomization [ 16 , 17 , 18 ], atomic fluorescence spectrometry (AFS) [ 21 ] inductively coupled optical emission spectrometry (ICP-OES) [ 16 , 22 ], inductively coupled plasma mass spectrometry (ICP-MS) [ 23 , 24 ], and X-ray fluorescence (XRF) [ 19 , 25 ], have been the most frequently employed. On the contrary, electroanalytical [ 26 ] or neutron-activation-based techniques, such as neutron activation analysis (NAA), have been used to a lesser extent [ 27 , 28 , 29 ].…”