of halogen elements [4]. In such cases, a typical dilution of the sample
may be necessary before the analysis [5], or a preliminary separation
and/or preconcentration step may be required to eliminate interferences
and/or to improve detection limits for metals in the low μg L−1
range [6]. Moreover, when the analysis is performed by using solid
sorbents followed by spectrophotometric techniques, an additional
elution step after the preconcentration procedure is necessary to
recover the species in an appropriate medium.