Speciation analysis of vanadium in natural water samples by electrothermal vaporization inductively coupled plasma optical emission spectrometry after separation/preconcentration with thenoyltrifluoroacetone immobilized on microcrystalline naphthalene

A sensitive and simple method for low temperature electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) determination of V(IV) and V(V) after separation/preconcentration by a micro-column packed with immobilized thenoyltrifluoroacetone (TTA) on microcrystalline naphthalene has been developed. Thenoyltrifluoroacetone was used as both a chelating agent for micro-column separation/preconcentration and a chemical modifier for ETV-ICP-OES determination of vanadium. Both vanadium species could be trapped by micro-column at pH 4.0, and the vanadate (VO2+) ion could be collected selectively at pH 2.4. Solid material loaded with analyte in the micro-column was dissolved with 100 μL of acetone containing 2.0 mmol L−1 TTA and the vanadium was determined subsequently by ETV-ICP-OES. The concentration of vanadyl (VO2+) ion was calculated by subtracting the vanadate concentration from the total concentration of vanadium. Under the optimized experimental conditions, the detection limit (3σ) for the preconcentration of 5 mL of aqueous solution is 0.068 μg L−1 for both species and the relative standard deviations were 4.3% for vanadium(V) and 4.8% for vanadium(IV) (c=10 μg L−1, n=7), respectively. The method was applied successfully to the determination of vanadium(IV) and vanadium(V) in natural water samples.