Room temperature ionic liquids enhanced chemical vapor generation of copper, silver and gold following reduction in acidified aqueous solution with KBH4 for atomic fluorescence spectrometry

Abstract

Room temperature ionic liquids (RTILs), as novel solvents, have many fascinating properties which make them of fundamental interest to all chemists. Herein, we report the first application of an RTIL in the chemical vapor generation (CVG) of transition and noble metals following reduction of acidified analyte solution with KBH₄. Copper, silver and gold were selected as model analytes, and N-butylpyridinium tetrafluoroborate ([N bupy][BF₄]) was used as a model RTIL. The RTIL-enhanced CVG of copper, silver and gold was evaluated by flow injection atomic fluorescence spectrometry (FI-AFS). The addition of [N bupy][BF₄] leads to a 4.8-, 2.7- and 3.6-times improvement in the CVG efficiencies for copper, silver and gold, respectively. Interference from Zn(II), Fe(III), Co(II), Ni(II), Pb(II), Se(IV) and As(III) was also reduced in the presence of [N bupy][BF₄]. The role of the RTIL was supposed to be inhibition of further coalescence of the metal nanoparticles which may constitute the volatile metal species leaving the solution and/or reaching the atomizer, and hence prevention of the loss of volatile metal species. With the consumption of a 0.5 mL sample solution, the detection limits (3s) for Cu, Ag and Au are 19, 15 and 6.3 μg L⁻¹, respectively. The precisions (RSD, n = 11) for eleven replicate measurements of the standard solution containing 50 μg L⁻¹Cu, Ag and Au were 4.4%, 5.2% and 4.7%, respectively. The developed RTIL-enhanced FI-CVG-AFS method was successfully applied to determination of trace Cu, Ag and Au in several certified biological and geological reference materials.