Flow injection wetting-film extraction system for flame atomic absorption spectrometric determination of cadmium in environmental waters

A newly simple flow injection wetting-film extraction system coupled to flame atomic absorption spectrometry (FAAS) has been developed for trace amount of cadmium determination. The sample was mixed on-line with sodium diethyl dithiocarbamate and the produced non-charged Cd(II)-diethyl dithiocarbamate (DDTC) chelate complex was extracted on the thin film of diisobutyl ketone (DIBK) on the inner wall of the PTFE extraction coil. The wetting-film with the extracted analyte was then eluted by a segment of the cover solvent, and transported directly to the FAAS for evaluation. All the important chemical and flow parameters were optimized. Under the optimized conditions an enhancement factor of 35, a sample frequency of 22 h⁻¹ and a detection limit of c_L = 0.7 μg l⁻¹ Cd(II) were obtained for 60 s preconcentration time. The calibration curve was linear over the concentration range 1.5-45.0 μg l⁻¹ Cd(II) and the relative standard deviation, R.S.D. (n = 10) was 3.9%, at 10.0 μg l⁻¹ concentration level. The developed method was successfully applied to cadmium determination in a variety of environmental water samples as well as waste-water sample.