Sensitive determination of trace molybdenum in natural waters using dispersive liquid–liquid microextraction and electrothermal atomic absorption spectrometry

Abstract

A simple, sensitive and rapid method involving dispersive liquid–liquid microextraction was developed for the determination of molybdenum using electrothermal atomic absorption spectrometry. After injection of a ternary mixture containing trichloroethylene (extractor solvent), ethanol (disperser solvent) and ammonium pyrrolidinedithiocarbamate (chelating reagent), the extraction of molybdenum into the aqueous phase occurs. The quantity of the element in the enriched phase was measured using electrothermal atomic absorption spectrometry. Under optimized conditions (pH 2.5, 2.0 mL of disperser solvent, 50 μL of extraction solvent, 50.0 μL of 0.10% m/v chelating solution and centrifugation at 3000 rpm for 2.5 minutes), the method has a detection limit of 0.013 μg L⁻¹, a quantification limit of 0.044 μg L⁻¹ and an enrichment factor of 75 for a sample volume of 5.0 mL. The certified reference material NIST 2781, Domestic Sludge, was used to assess the accuracy of the method. The proposed procedure was successfully applied to the determination of molybdenum in natural water samples.