The interfacial perimeter of nanogold and supports is often deemed as the catalytically active sites for many reactions, while the geometrical configuration of the interfacial perimeter at atomic scale is...

A new voltammetric method for the determination of chloramphenicol (CAP) is developed. The method is based on the reaction of chloramphenicol and zinc in HCl solution to form a new substance [I] which produced a sensitive oxidation peak at 0.825 V (vs. Ag/AgCl) in pH 7.0 phosphate buffer solutions using differential pulse voltammetry (DPV). There is a linear relationship between the intensity of the peak current and the concentration of CAP. Effects of different chemical and variables such as pH, heating time on the determination of CAP have been optimized. It had been discussed that the electrochemistry characteristic and the reaction mechanism. Calibration graphs were linear in the 0.8 to 30.0 μg mL −1 concentration range with a correlation coefficient of 0.9983. The relative standard deviation for 9 repetitive determinations of 10.0 μg mL −1 CAP was 2.7%. The method has been successfully applied to pharmaceutical formulations and spiked milk samples.

An inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol S (BPS). The proposed method is based on the inhibitory effect of BPS on the fluorescence quenching of rhodamine B (RhB) caused by potassium bromate in a dilute phosphoric acid medium. Under the optimal conditions of the experiment, the detection limit for BPS was 0.021 mg/L, and the linear range of determination was from 0.035 mg/L to 0.750 mg/L. The relative standard deviations of 11 measurements for 0.20 mg/L and 0.40 mg/L BPS solutions were 2.74 % and 1.87 %, respectively. The method was successfully applied to the determination of bisphenol S derived from commercially available plastic film samples in hot water. A possible reaction mechanism of the inhibitory effect of BPS on the fluorescence quenching of RhB was proposed.

A new fluorescent probe, 6-amino-1,3-naphthalenedisulfonic acid (ANDSA), has been developed for the determination of trace nitrite in different waters. This probe is based on the selective reaction of nitrite with ANDSA in hydrochloric acid solution to form the corresponding diazonium acid in sodium hydroxide solution at room temperature. The diazonium acid produced has high fluorescence intensity at 488 nm (excitation at 367 nm), whereas ANDSA has high fluorescence intensity at 465 nm (excitation at 354 nm). The synchronous fluorescence (Δλ = 121 nm) spectrum and the first-derivative synchronous fluorescence spectrum of diazonium acid greatly overlapped with those of ANDSA. The zero-crossing method was used to measure the first-derivative value (dF/dλ) of the first-derivative spectra, in which physical separation of excess ANDSA was unnecessary. The zero-crossing point was located at 351.2 nm for ANDSA, at which dF/dλ of diazonium acid was proportional to the nitrite concentration. Therefore, dF/dλ at 351.2 nm was selected as the analytical signal. Under the optimized experimental conditions, the signal intensity was linear over a nitrite concentration range of 0.006-0.075 mg L, with a correlation coefficient better than 0.9994. The limit of detection was 2.1 μg L for the determination of nitrite by the proposed method. The relative standard deviation of the method for the determination of nitrite in real water samples was below 2.45%, and the corresponding recoveries were between 95.7% and 104.1%. The validity of the proposed method was further confirmed by comparison with the reference method with use of the t test. Graphical abstract ANDSA reacts with nitrite to form diazonium acid with higher fluorescence intensity. For ANDSA, dF/dλ was zero at 351.2 nm, whereas dF/dλ of diazonium acid at 351.2 nm was close to the maximum value.

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