Synergetic enhancement effect of room temperature ionic liquids and ammonium pyrrolidine dithiocarbamate on the chemical vapor generation of iron, cobalt and nickel in environmental and biological samples by atomic absorption spectrometric determination

Abstract

A new method based on chemical vapor generation (CVG) coupled with flame atomic absorption spectrometry (FAAS) was developed for the determination of iron, cobalt and nickel in environmental and biological samples. Room temperature ionic liquids (RTIL) combined with ammonium pyrroldinedithiocarbamate (APDC) were used to synergetically enhance the CVG of iron, cobalt and nickel. The addition of RTIL leads to 2.5, 3.2, 3.0 times improvement in the CVG efficiencies of Fe, Co and Ni, respectively. The efficiencies for the CVG of Fe, Co and Ni in the presence of RTIL and APDC were 42%, 61% and 54%, respectively. Volatile species of iron, cobalt and nickel were effectively generated through reduction of acidified analyte solutions with KBH₄ in the presence of 0.02% or 0.01% (m/v) APDC and 0.1% or 0.2% (m/v) 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM]PF₆). Some parameters that influenced CVG and subsequent determination were evaluated in detail, such as the concentrations of RTIL, APDC, nitric acid (HNO₃) and KBH₄; flow rates of carrier gas, lengths of reaction tube and transfer tube, as well as interferences. Under optimized conditions, the detection limits (LODs) for Fe, Co and Ni were 18, 14 and 11 ng mL⁻¹, respectively. Relative standard deviations for five replicate determinations of the standard solution containing 500 ng mL⁻¹Fe, Co and Ni were 5.3%, 4.6% and 4.3%, respectively. The proposed method was successfully applied to the determination of iron, cobalt and nickel in certified environmental and biological reference materials with satisfactory results.