Highly Sensitive Spectrofluorometric Determination of Trace Amount of Gallium with Salicylaldehyde-5-bromo-salicyloylhydrazone

オhe fluorescent reagent, salicylaldehyde-5-bromo-salicyloylhydrazone (SABSH) was synthesized and its ionization constants were determined spectrophotometrically. The fluorescent reaction of this reagent with gallium was studied. Based on this chelation reaction, a highly sensitive spectrofluorometric method was developed for the determination of gallium in a ethanol-water (3+2, V/V) medium at pH 2.3. Under these conditions, the GaⅢSABSH complex has excitation and emission maxima at 390 and 457 nm, respectively. The linear range of the method is from 0.0 to 1×10-4 g/L and the detection limit is 4×10-7 g/L of gallium when a standard additions method is used. The molar ratio of gallium to the reagent is 1∶1. Interferences were evaluated. The method was successfully applied to the determination of gallium in soil samples. Extraction with n-butyl acetate from 6 mol/L hydrochloric acid medium was used to separate gallium from the interfering elements in the soil samples.

Spectrofluorometric Study of the Inclusion Complexation of Fluorescent Whitening Agents and β-Cyclodextrins

The inclusion complexation behavior of 2,5-Bis(5-tert-butyl-benzoxazol-2yl)-thiophene (UVOB) with native β-cyclodextrin (βCD) and βCD-monochlorotriazinyl (βCD-MCT) was evaluated by fluorescence spectroscopy. The association constant (Ks), stoichiometry, , and were evaluated at 25℃ ± 0.1℃ in phosphate buffer solution (pH = 10.5, 0.1 mo•dm–3) in order to find out the complex formation ability and stability. Fluorescence enhancement for UVOB and UVBNB with both CDs has been observed as a result of the complex formation. A stoichiometry 1:1 for UVOB in both CDs was observed;a stoichiometry 3:1 for UVBNB in both CDs has been observed. The Ksvalues for UVOB were 4916 ± 137 M–1 and 655 ± 19 M–1 (acetone: water 90/10, v/v) with βCD and βCD-MCT, respectively. The value obtained indicates a spontaneous and stable complex formation, but the complex βCD-UVOB showed high Ks value as an indicative of a high concentration of complex formed. Additionally, Ks and thermodynamic parameters and were evaluated in a commercial product UVBNB (UVOB, 13%, v/v). In aqueous solution, the values obtained were 2552 ± 115 and 1787 ± 75 M–1 respectively. Complexation of UVOB with CDs is an interesting approach for utilization of UVOB in aqueous systems without the need of solvents and or surfactants used in commercial product (UVBNB).

Histidine‑Stabilized Copper Nanoclusters as a Fluorescent Probe for Selective and Sensitive Determination of Vitamin B_(12)

Herein,we report the highly sensitive and selective determination of vitamin B_(12)(VB_(12))using histidine-stabilized copper nanoclusters(His-CuNCs)as a fluorescent probe by the spectrofluorometry method.The as-synthesized His-CuNCs were characterized by UV–Vis absorption,steady-state emission,and high-resolution transmission electron microscopy measurements.His-CuNCs exhibited an emission maximum around 443 nm,when excited at 350 nm.The emission intensity of His-CuNCs was significantly quenched by the addition of VB_(12),hinting that the synthesized probe can be employed for sensing of VB_(12).Based on the decrease in emission intensity,the concentration of VB_(12) was determined and the emission intensity of His-CuNCs can be quenched by VB_(12) via fluorescence resonance energy-transfer mechanism.His-CuNCs showed high selectivity toward the determination of VB_(12) in the presence of other potentially interfering vitamins,cations,and anions.In addition,the proposed sensing platform displayed a sensitive response to VB_(12) in the linear range of 4.00–28.00×10^(−6) mol dm^(−3) with a limit of detection of 3.30×10^(−9) mol dm^(−3).The proposed sensing system is simple,low cost,selective,and sensitive for the determination of VB_(12) in biological samples.