Determination of lead in complex sample matrices by atomic fluorescence spectrometry: optimisation of online hydride generation

Lead hydride or plumbane (PbH4) generation was optimised by exploiting a simple flow-injection method coupled to atomic fluorescence spectrometry (HG-AFS), and allowing ultra-trace lead determination. Plumbane was generated through two methods: (1) 5% (v/v) H2O2 was employed as oxidant with 1.5% (m/v) KBH4 as a reducing agent and 1.5% (v/v) HCl solution; (2) with 1.5% (m/v) K-3[Fe(CN)(6)] as an oxidant/sensitiser, 1% (m/v) KBH4 as a reducing agent and 1.5% (v/v) HCl. Variables such as reagent concentrations, flow rates and sample and reagent volumes were tested and critically compared. The best results were obtained with potassium ferricyanide K-3[Fe(CN)(6)], achieving a detection limit of 0.03 mu g PbL-1 and a relative standard deviation (RSD) of 1.1%. The selected method was validated by analysis of certified reference materials such as SRM-2976 (mussel tissue) and BCR-610 (groundwater), with good agreement with the certified values. The developed methodology was successfully applied to different environmental sample matrices, such as rain water, tap water, ground water, spring water and drinking water, and biological samples, i.e., human blood, plasma and serum.