In recent years, the safety of copper in drinking water has increasingly been questioned. Copper speciation is an important factor that affects its bioavailability and toxicity; thus, it is critical to investigate the speciation of copper that is ingested from food and drinking water during in vitro digestion. After digestion, water- and food-derived copper formed 60 ± 4% 0.1–1 kDa and 49 ± 6% 10–1,000 kDa copper complexes, respectively. Under simulated fasting drinking water conditions, up to 90 ± 2% 0.1–1 kDa copper complexes formed. In addition, using ion selective electrode analysis, water-derived copper was detected that contained higher Cu²⁺ concentrations after digestion than those of food-derived copper. These results indicate that water-derived copper forms smaller-sized species and exhibits higher Cu²⁺ concentrations during digestion than those of food-derived copper, thereby highlighting the importance of reassessing the safety limit for copper in drinking water.

A rapid and efficient method based on a novel nitrogen-doped porous graphene nanostructure (NDPG) was used for the speciation of mercury in water and human blood samples by the CV-AAS. The mixture of the NDPG, ionic liquid, and acetone was rapidly injected into the human blood, water, and food samples for mercury separation by the cloud point assisted dispersive ionic liquid-micro solid-phase extraction (CPA-DIL-μ-SPE) at pH 7.5. The UV-microwave accessory converted the organic mercury (R-Hg) to inorganic mercury, and total mercury (TM) was determined. Finally, the organic mercury was calculated by subtracting the inorganic and entire mercury contents. By optimizing, the linear range, LOD, and enrichment factor were obtained (0.01–6.80 µg/L; 0.005–3.60 µg/L), (2.6 ng/L; 1.2 ng/L) and (9.8; 20.2) for the mercury species in human blood and water/food samples, respectively (Mean of RSD < 1.9 %). The CRM samples obtained the validation of the procedure.

A preconcentration procedure based on cloud point extraction and back-extraction (CPE-BE) was proposed for speciation of inorganic vanadium (V⁴⁺ and V⁵⁺) followed by determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). Two consecutive steps are used in this technique. The traditional CPE technique was applied as a first step, V⁵⁺ reacts with bis(3,4-dihydroxybenzylidene)isophthalohydrazide (DHBIP) forming a hydrophobic complex at pH 7.0. The formed complex is then entrapped in a surfactant-rich phase of Triton X-114, while V⁴⁺ kept in the aqueous phase. Following this stage, a back-extraction step was performed to minimize the deteriorating effect of the organic matrix on the plasma performance. For this purpose, the surfactant-rich phase containing the analyte was incubated at 45 °C with 1.0 mL of 1.0 mol L⁻¹ of HNO₃ solution for 15 min. Finally, the analyte in the aqueous phase was determined by ICP-OES. The total vanadium was determined as V⁵⁺ after oxidation of V⁴⁺ by using hydrogen peroxide. The calibration graph is linear from 0.4–750.0 μg L⁻¹ for V⁵⁺ at the optimum conditions (pH 7.0, 10⁻⁴ mol L⁻¹ DHBIP, 0.1 % (v/v) Triton X-114 and 45 °C). The detection and quantification limits of V⁵⁺ were 0.12 μg L⁻¹and 0.40 μg L⁻¹, respectively, with an enrichment factor of 49.5, and the relative standard deviation was less than 2.5 % (n = 7, c = 10 μg L⁻¹). The method has been used for speciation of inorganic V in water samples and determination of total V in cabbage, carrots, mint, and tomato samples with satisfactory results.

A novel ultrasound-assisted liquid phase microextraction (UALPME) based on environmental friendly extractants, deep eutectic solvent (DES) was first time presented for speciation of selenium. In present study, five DES solvents of different composition was prepared and used as efficient extractive medium for hydrophobic chelate of Se(IV) with 3,3′-Diaminobenzidine (DAB). The total inorganic Se species were determined after pre-reduction of Se(VI) to Se(IV), prior to applying developed method. The concentration of Se(VI) was calculated by the difference of Se(IV) values and total selenium contents. The concentration of Se in DES rich phase was measured with electrothermal atomic absorption spectrometer (ETAAS). The effects of different parameters on extraction efficiency of study analyte, including pH, ligand concentration, type and volume of DES, sonication time, volumes tetrahydrofuran and aqueous samples were examined. At the optimum conditions, limit of detection and quantification, preconcentration factor, and relative standard deviation (RSD %) were determined as 4.61ngL⁻¹, 15.4ngL⁻¹, 50% and 4.1%, respectively. The accuracy of the presented method was confirmed by analysis of certified reference material and standard addition method for different water and ice tea samples. The developed method was effectively applied to real water and food samples.