Fabrication of cefotaxime sodium-functionalized gold nanoclusters for the detection of copper ions in Chinese herbal medicines.

Antibiotic-based gold nanoclusters (AuNCs) are a good sensing platform for specific recognition; however, the related studies are few. Herein, a simple and facile strategy was proposed for the fabrication of bright blue fluorescent AuNCs through the degradation product (DCTX) of cefotaxime sodium that induced the reduction of HAuCl4. Various analytical techniques were applied to characterize the prepared AuNCs@DCTX. AuNCs@DCTX exhibited a strong emission peak centered at 420 nm and a quantum yield of 11.8%. Furthermore, an aggregation-induced fluorescence quenching mode endowed the AuNCs@DCTX probe with good specificity and sensitivity for Cu2+ detection. The proposed probe had a linear range of 0.01-40 µM, a precision with a relative standard deviation of 1.2% (n = 8), and a detection limit of 8 nM (signal/noise = 3). Interestingly, the probe could be reused through switching the "off" and "on" states by the addition of Cu2+ and EDTA. The practicality of the sensing platform was investigated for the determination of Cu2+ in four Chinese herbal medicines (CHMs), and the results were in accordance with those obtained by the FAAS method. This study has provided an alternate way for the fabrication of thiolate-protected AuNCs for sensing applications.

Investigation of 1-Dodecylimidazolium Modified Filter Papers as a Thin-Film Microextraction Phase for the Preconcentration of Bisphenol A from Plant Oil Samples.

Based on the tunability of ionic liquids (ILs) according to the specific requirement of an application, 1-dodecylimidazolium chloride with amphiphilic structures was chemically fabricated on the surface of filter papers (DIL-FPs) for the first time. After synthesis, DIL-FPs was characterized by scanning electronic microscopy, energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. DIL-FPs was used as a novel thin-film microextraction (TFME) phase for the preconcentration of amphiphilic bisphenol A from plant oil samples. The related extraction variables were studied in a spiked sunflower seed oil. Under the optimal conditions, the linear range was 5.0 - 1000 µg L-1 with a correlation coefficient of 0.9976. The limit of detection (S/N = 3) and the enrichment factor of the proposed method were 2.7 µg L-1 and 118, respectively. The intra-day precision and inter-day precision for six repeated determinations were 2.3 and 4.9%, respectively. These plant oil samples used in this work were free of bisphenol A contaminations. The recovery study carried out in different plant oil samples and mean recoveries ranged from 77.16 to 97.10%. The developed DIL-FPs extraction film phase followed by HPLC-UV provides a potential pretreatment strategy for the analysis of weak organic acid compounds in plant oil samples.

[Speciation analysis of selenium by flow-injection catalytic spectrophotometry].

A new flow-injection catalytic spectrophotometric method was proposed for the determination of Se(IV) based on its catalytic effect on the reduction reaction of azure I by Na2S in pH 7.0 citric-acid sodium-hydrogen-phosphate buffer solution. Some different schematic diagrams of FIA were compared. Effects of the flow rates of reagents and sample, the medium and its acidity, the temperature, and coexistent substances were studied respectively. The amount of used reagents and the experimental conditions for sampling volume and coil length were optimized by using the controlled and weighed centroid simplex method. The Linear range of the determination is 0.1-2.0 mg x L(-1), the detection limit is 0.015 mg x L(-1), the relative standard deviation is less than 3.1%, and the sampling frequency is 120 samples per hour. The method has been applied to the determination of organic selenium and inorganic selenium in garlic and selenium-yeast. It was found that garlic had a strong enriching effect for selenium, and the conversion ratio of organic selenium decreased with increasing the concentration of selenium in the environment. The recovery of this method is 97.1%-104.3%.