Trace amounts of iron were determined by flow injection catalytic kinetic spectrophotometry,based on the catalytic effects of iron on the redox reaction between potassium bromate and 4,4′-tetramethyldiaminodiphenylmethane in the presence of potassium iodide in HAc-NaAc buffer solution.The measurements were conducted at 602nm of an unstable blue product of the reaction.Flow injection technique was utilized to precisely control the timing of merging and reaction of the reagents and samples.A stopped-flow approach was used to improve the sensitivity of the system.A detection limit of 2.6×10-9g/mL was achieved at a sampling frequency of 45/h.Calibration graphs were linear for ranges of 0～0.4mg/L for Fe(III).The proposed method was validated by the analysis of a national reference material and applied to the analyses of several water samples,with recoveries of 95.9%to 97.3%.
CdSe/CdS quantum dots(QDs) functionalized by thiourea(TU) were synthesized and used as a fluorescent sensor for mercury ion detection.The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid(TGA).It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg^(2+).The quantitative detection of Hg^(2+) with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg^(2+) added in the range of1-300 μg L^(-1).A detection limit of 0.56 μg L^(-1) was achieved.The sensor showed superior selectivity for Hg^(2+) and was successfully applied to the determination of mercury in environmental samples with satisfactory results.
A simple and selective method for the determination of silver ions was developed by utilizing the redshift in emission wavelength of the core-shell CdSe/CdS quantum dots(QDs) functionalized with rhodanine upon the addition of Ag^+.A linear relationship was observed between the shift and the increase in concentration of Ag^+ in the range of 0.0125-12.5 μmol/L The mechanism of the red-shift was investigated and suggested that the coordination between Ag^+ and rhodanine on the QDs surface caused an increase of particle size,which resulted in the red-shift of the QDs' emission wavelength.A detection limit of 2 nmol/L was achieved.The developed method showed superior selectivity and was successfully applied to the determination of silver in environmental samples.
