Yaghoub Assadi

In this study a novel methodology is proposed for utilizing solvents less dense than water by using a dispersive liquid–liquid microextraction (DLLME) technique. Conventional microextraction vessels and facile strategy have been used. We have avoided using routine microextraction solvents in the DLLME procedure that are mostly chlorinated, dense, environmentally hazardous and expensive which limits the application of this method to some extent. The aforesaid process has been combined with fiber optic-linear array detection spectrophotometry (FO-LADS) with charge-coupled device (CCD) detector benefiting of a micro-cell. L-Ascorbate was selected as a model compound and the proposed method was carried out for preconcentration and assay of iodine produced by reduction of potassium iodate in fruit juices, soft drinks and pharmaceutical preparations. The influences of the various analytical parameters on the microextraction procedure and oxidation reaction have been evaluated and optimized. The accuracy of the method was confirmed by parallel analyses as the reference method (ISO 6557/2). The calibration curve was linear in the range of 1.76–26.40 μg mL⁻¹ of L-ascorbate with a correlation coefficient (r) of 0.9912. The LOD obtained from the calibration curve was 0.40 μg mL⁻¹.

A new simple and sensitive method has been proposed for rapid determination of trace levels of silver in environmental water samples, using dispersive liquid–liquid microextraction (DLLME) prior to its microsample introduction-flame atomic absorption spectrometry. Under the optimum conditions, the linear range was 0.1–7 µg L⁻¹ and limit of detection was 0.018 µg L⁻¹. The relative standard deviation for 0.50 and 5.00 µg L⁻¹ of silver in water sample was 4.0 and 1.7%, respectively. The relative recoveries of silver from tap, well, river, and seawater samples at spiking levels of 1.00 and 5.00 µg L⁻¹ were in the range of 86.4–98.6%.

A simple and effective homogeneous liquid–liquid extraction method has been used for the simultaneous extraction and preconcentration of cobalt, copper, and nickel after the formation of complex with 4‐benzylpiperidinedithiocarbamate potassium salt (K‐4‐BPDC), and later they were determined by flame atomic absorption spectrometry (FAAS) using (water/tetrabutylammonium ion (TBA⁺)/chloroform) as a ternary component system. The phase separation phenomenon occurred by an ion‐pair formation of TBA⁺ and perchlorate ion. After the optimization of complexation and extraction conditions ([K‐4‐BPDC]=2.0×10⁻⁴ mol l⁻¹, [TBA⁺]=2.0×10⁻² mol l⁻¹, [CHCl₃]=60.0 µl, [ClO₄ ⁻]=2.0 ×10⁻² mol l ⁻¹ and pH=6.0), a preconcentration factor of 200 was obtained for only 10 ml of the sample. The analytical curves were linear in the range of 20–1500, 15–2000, 35–1600 µg l⁻¹ and the limits of detection were 10, 5, and 15 µg l⁻¹ for Co²⁺, Cu²⁺, and Ni²⁺, respectively. The proposed method was applied for the extraction and determination of Co²⁺, Cu²⁺, and Ni²⁺ in natural water samples with satisfactory results.