Determination of Cobalt at ng ml-1 Level in Water Using the Electrophilic Substiution Complexation between Co(II) and Chlorophosphonazo- p-Cl-Cu(II) Complex

Colorimetric and fluorescent chemosensor for highly selective and sensitive relay detection of Cu2+ and H2PO4- in aqueous media

In this manuscript, a new colorimetric and fluorescent chemosensor (T) was designed and synthesized, it could successively detect Cu²⁺ and H₂PO₄^- in DMSO/H₂O (v/v=9:1, pH=7.2) buffer solution with high selectivity and sensitivity. When added Cu²⁺ ions into the solution of T, it showed a color changes from yellow to colorless, meanwhile, the green fluorescence of sensor T quenched. This recognition behavior was not affected in the presence of other cations, including Hg²⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Cr³⁺, and Mg²⁺ ions. More interestingly, the Cu²⁺ ions contain sensor T solution could recover the color and fluorescence upon the addition of H₂PO₄^- anions in the same medium. And other surveyed anions (including F^-, Cl^-, Br^-, I^-, AcO^-, HSO₄^-, ClO₄^-, CN^- and SCN^-) had nearly no influence on the recognition behavior. The detection limits of T to Cu²⁺ and T-Cu²⁺ to H₂PO₄^- were evaluated to be 1.609×10^-8M and 0.994×10^-7M, respectively. In addition, the sensor T also could be served as a recyclable component and the logic gate output was also defined in sensing materials. The test strips based on sensor T were fabricated, which acted as a convenient and efficient Cu²⁺ and H₂PO₄^- test kits.

Determination of cobalt in water samples by atomic absorption spectrometry after pre-concentration with a simple ionic liquid-based dispersive liquid-liquid micro-extraction methodology

A rapid dispersive liquid-liquid micro-extraction (DLLME) methodology based on the application of 1-hexylpyridinium hexafluorophosphate [C6py][PF6] ionic liquid (IL) as an extractant solvent was applied for the pre-concentration of trace levels of cobalt prior to determination by flame atomic absorption spectrometry (FAAS). 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was employed as a chelator forming a Co-PMBP complex to extract cobalt ions from aqueous solution into the fine droplets of [C6py][PF6]. Some effective factors that influence the micro-extraction efficiency include the pH, the PMBP concentration, the amount of ionic liquid, the ionic strength, the temperature and the centrifugation time which were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and the enrichment factor were 0.70 µg L−1 and 60, respectively. The relative standard deviation (RSD) for six replicate determinations of 50 µg L−1 Co was 2.36%. The calibration graph using the pre-concentration system was linear at levels 2–166 µg L−1 with a correlation coefficient of 0.9982. The applicability of the proposed method was evaluated by the determination of trace amounts of cobalt in several water samples.