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Boletus brunneissimus Chiu carbon dots (Bb-CDs) with good fluorescence performance were successfully prepared by the hydrothermal method (200°C, 12 h) using the edible fungus Boletus brunneissimus Chiu as the carbon source. The Bb-CD fluorescent nanoprobe was applied to detection of riboflavin, and its fluorescence-quenching mechanism was investigated. The structure and optical properties of the Bb-CDs were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. In the riboflavin concentration (C) range of 0–50 μM, the fluorescence-quenching effect of the Bb-CDs (y) showed a good linear relationship with the riboflavin concentration. The linear equation was y = 0.00304C + 0.02151 (R2 = 0.99497), and the detection limit was 45 nM. Therefore, the Bb-CDs showed high detection sensitivity and a low detection limit for riboflavin. Moreover, the fluorescence-quenching mechanism of the Bb-CDs by riboflavin belonged to the fluorescent inner filter effect. The Bb-CDs were successfully used as a fluorescent nanoprobe to detect riboflavin in actual fruit samples, which provides a new concept for application of CDs to biological detection. [ABSTRACT FROM AUTHOR]

A novel preconcentration technique termed suspension dispersive solid phase extraction (SDSPE) was developed for selective separation and preconcentration of cobalt, nickel, and copper in environmental water. The method is based on the reaction of zinc sulfate and sodium hydroxide to form zinc hydroxide. The suspension results from the dispersion of the fine particles of the sorbent in the aqueous sample. The complexes of metal ions in the bulk aqueous sample with 1-(2-pyridylazo)-2-naphthol (PAN) were loaded on sorbents. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was eluted by methanol and determined by flame atomic absorption spectrometry. Key parameters such as the type and mass of sorbent, type and volume of eluent, concentration of the chelating agent, equilibration time, and sample volume were optimized and an enrichment factor of 20 was obtained with a sample volume of 40 mL. The limits of detection for Co, Ni, and Cu were 2.4, 1.7, and 1.5 µg L−1, respectively. The relative standard deviations were 4.3%, 2.7%, and 1.6% at 10 µg L−1for Co, Ni, and Cu, respectively. The method was successfully employed for the determination of these metals in environmental waters. [ABSTRACT FROM AUTHOR]

A novel metal-doped carbon quantum dot, zinc-chlorine co-doped carbon quantum dots (Zn/Cl-CQDs), has been developed for the fluorescent probe detection of vitamin B2 and the analysis of the correlation properties of this carbon quantum dot and vitamin B2. Stability experiments demonstrate that Zn/Cl-CQDs possess good fluorescence properties under alkaline conditions. However, when vitamin B2 is added into Zn/Cl-CQDs, the fluorescence intensity decreases sharply, indicating that the fluorescence sensor shows rapid and sensitive detection of vitamin B2 under the static quenching. Lastly, the use of Zn/Cl-CQDs in the detection of vitamin B2 tablets and vitamin B2-rich fruits resulted in recovery rates of 98.2% and 100.6%, respectively. Therefore, this method can be well applied to the detection and analysis of vitamin B2, and has great development prospects in the pharmaceutical industry and food monitoring fields., Competing Interests: All authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

A simple and practical extraction method of supramolecular solvents (SUPRAS) was developed for separation and enrichment of trace amounts of palladium (Pd) and silver (Ag) in water samples prior to flame atomic absorption spectrometry (FAAS) analysis. The SUPRAS selected was made up of an aqueous solution containing tetrahydrofuran and nonanoic acid. Pd and Ag reacted with diethyldithiocarbamate to form hydrophobic chelates, which were extracted into the vesicles of SUPRAS. Different parameters such as the concentration of chelating agent, sample pH, supramolecular solvent and the effect of foreign ions were studied. Under the optimal conditions, the linear ranges of Pd and Ag were from 10 to 1,000 μg/L. The relative recoveries of Pd and Ag in tap and river water samples at the spiking level of 10 ug/mL ranged from 90.8 to 116%. The relative standard deviations were 3.6-4.0% (n = 9), the limits of detection were 2.8 and 1.9 μg/L and the enrichment factors were 36 and 18 for Pd and Ag, respectively. The quantification limits were 3.2 and 2.4 μg/L. The method was successfully applied to the determination of Pd and Ag in water samples.