Light-absorption ratio variation approach to determination of nickel (II) in ng/ml level with 1, 5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan

Determination of dissolved nickel in natural waters using a rapid microplate fluorescence assay method

A new microplate analytical procedure is described for the determination of nickel (Ni²⁺) ions in natural water samples. A lophine analogue fluorescent sensor was synthesized and a spectral study showed a selective fluorescence quenching effect of chemical sensor by Ni²⁺ under optimized conditions. Density functional theory (DFT) calculations confirmed the formation of a Ni(II)L₃ complex obtained by the Job plot. The calculations showed that the fluorescence emission peak of L collapses due to the distortion of L in the complex. The simple and fast microplate procedure allowed us to quantify Ni²⁺ with a linear response from 1.6 to 40 µg L^-1 and a quantification limit of 5.4 µg L^-1 without the need of a preconcentration step. The optimized procedure using high-throughput microplate assay has been applied for the determination of Ni²⁺ in natural water samples with good analytical performances.

Ratiometric fluorogenic determination of endogenous hypochlorous acid in living cells

Hypochlorous acid (HClO) is one of the most important ROS (reactive oxygen species) and common pollutant in tap-water. However, the determination of HClO with fast response and high sensitivity/selectivity is still an urgent demanding. Here we fabricated a ratiometric fluorescent probe RC based on TBET (through-bond energy transfer) on the platform of coumarin and rhodamine with the thiosemicarbazide group as the linker. This probe could display the characteristic fluorescence emission of coumarin. Upon addition of HClO, the linker was reacted into an oxadiazole, resulting in the opening of spiro-ring of rhodamine. The resultant then gives ratiometric fluorogenic changes. The probe exhibits fast response and high selectivity and sensitivity towards HClO with a low limit of detection (~140 nM). Eventually, RC is successfully applicated for determining spiked HClO in water samples and imaging endogenous HClO in living cells.

Highly sensitive determination of Cu(II) iron in ng/mL level in natural waters using Sulfochlorophenol S

The highly sensitive complexation of Cu(II) with Sulfochlorophenol S (SCPS) at pH 4.03 was characterized by the spectral correction technique. This reaction was used to determine the Cu(II) content in various sources by the light-absorption ratio variation approach (LARVA). The limit of detection of Cu(II) was only 1.35 ng/mL, thus facilitating the direct monitoring of natural water. The Cu(II) contents in the Huangpu River, Yangtze River, and Taihu Lake of China were determined with satisfactory results, and the recovery rates of Cu(II) using SCPS were between 94.5 and 102.6 %.

The effects of copper ions on the catalytical degradation of azo dye acid chrome blue K

The effects of Cu2+ on the catalytical degradation of acid chrome blue K (ACBK) in UV-TiO2 and H2O2 processes were studied. In these two processes, Cu2+ markedly depressed the catalytical degradation of ACBK by its interaction with ACBK. Through this interaction, the new complex Cu(ACBK)2 formed. The formation of this new complex was favorable to protect some groups in ACBK from the oxidation of reactive oxygen generated in UV-TiO2 and H2O2 processes, and consequently had suppressing effects on degradation of ACBK. In addition, Cu2+ also inhibited the degradation of ACBK in UV-TiO2 process by influencing the adsorption of ACBK on the surface of TiO2 particles.

Continuous flow analysis combined with a light-absorption ratio variation approach for determination of copper at ng/ml level in natural water

The complexation between Cu(II) and naphthochrome green (NG) is very sensitive at pH 4.09 with the formation of complex ion [Cu(NG)2(H2O)2](2-). It can thus used for the determination of Cu(II) by the light-absorption ratio variation approach (LARVA) with a good selectivity. Both the ordinary detection procedure and continuous flow analysis (CFA) were carried out, where the latter is fit for continuous and rapid analysis of samples. The limit of detection (LOD) of Cu(II) is only 1 ng/ml, which is favorable for direct monitoring of natural water. About 30 samples could be analyzed per hour by CFA. Cu(II) contents in Yangtze River, West Lake, Taihu Lake of China and seawater near Shanghai were determined with satisfactory results. The CFA-LARVA spectrophotometry was the first to be coupled and it will play an important role in the in-situ analysis of natural water quality.

A novel detection approach based on chromophore-decolorizing with free radical and application to photometric determination of copper with acid chrome dark blue

A novel detection approach named chromophore-decolorizing with free radicals is developed for determination of trace heavy metal. The hydroxyl radicals (HO) generated from Fe(III) and hydrogen peroxide will oxidize the free chromophore into almost colorless products. The copper-acid chrome dark blue (ACDB) complexation was investigated at pH 5.07. In the presence of Fe(III) and hydrogen peroxide, the excess ACDB was decolorized in the Cu-ACDB reaction solution, and the final solution contained only one color compound, the Cu-ACDB complex. After oxidation of free hydroxyl radicals, the complexation becomes sensitive and selective and it has been used for the quantitation of trace amounts of Cu(II) dissolved in natural water. Beer's law is obeyed in the range from 0 to 0.500 microg mL(-1) Cu(II) and the limit of detection is only 6 microg L(-1) Cu(II). Besides, the Cu-ACDB complex formed was characterized.

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

The chromophore chlorophosphonazo-p-Cl (PCCPA) was used to complex Co(II) and Cu(II) at pH 9.18. The formation of Co(PCCPA)2 and Cu(PCCPA)2 complexes were characterized by the spectral correction technique. Co(II) could competitively substitute Cu(II) from the Cu(II)-PCCPA complex via electrophilic effect. With the assistance of the light-absorption ratio variation approach, the electrophilic substitution complexation showed a high selectivity and good sensitivity with 1.9 ng mL(-1) of LOD. The proposed method has been applied to the direct detection of Co(II) in surface water and wastewater with good percent of recovery.