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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]

Magnesium (Mg) plays an important role in numerous physiological and biochemical processes in plants. However, Mg deficiency is common worldwide, especially in greenhouse vegetable systems, due to the overuse or misuse of fertilizers. This study investigated the effects of different Mg application strategies in alleviating Mg deficiency of tomatoes in PE-film covered greenhouse. Six field treatments were used: conventional fertilization practice (C), conventional fertilization + soil warming (CW), conventional fertilization + Mg applied to soil (C + MgS), conventional fertilization + Mg applied as foliar application (C + MgF), conventional fertilization + Mg applied to soil and foliar application (C + MgSF), and conventional fertilization + Mg applied to soil and foliar application with soil warming (C + MgSFW). Foliar spray of Mg fertilizer (C + MgF, C + MgSF, and C + MgSFW) increased the total Mg uptake and Mg content of functional leaves in both winter-spring and autumn-winter seasons. Soil warming treatments (CW and C + MgSFW) were also beneficial for Mg uptake and chlorophyll biosynthesis compared with no-warming treatments (C and C + MgSF), especially in autumn-winter season. Additionally, Mg fertilizer application and soil warming increased tomato yields; the C + MgSFW treatment had the highest increase in yields compared with the C treatment. Therefore, foliar Mg fertilizer application combined with soil warming, while considering seasonal variation, is feasible for reducing Mg deficiency in tomatoes under PE-film covered greenhouse vegetable systems. [ABSTRACT FROM AUTHOR]

Solvent sublation, a surface chemical technique, was used to separate and concentrate benzo(a)pyrene from soil followed by determination using high-performance liquid chromatography with fluorescence detection. In the pretreatment, the effects of the sublation solvent, gas flow rate, and sublation time on the efficiency were investigated. Under the optimized conditions, the method showed good linearity in the range from 0.05 to 100 µg/L with an excellent correlation coefficient (r = 0.9981). The limit of detection was 0.24 µg/kg. The method was efficient and the recovery obtained with fortified soil was 88.2 to 105.3%, indicating that solvent sublation is an alternative approach to preconcentrate benzo(a)pyrene in soil. [ABSTRACT FROM PUBLISHER]

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]