Main content of VB3 and VB7 in the tea.

<p>Main content of VB3 and VB7 in the tea.</p

The synthesis procedure of AEAO.

<p>The synthesis procedure of AEAO.</p

Generalized One-Pot Strategy Enabling Different Surface Functionalizations of Carbon Nanodots to Produce Dual Emissions in Alcohol–Water Binary Systems

Fluorescent dual-emission carbon nanodots (DECNDs), which contained two different emitters, the blue emitters (λ_ex = 315 nm, λ_em = 386 nm) and the yellow emitters (λ_ex = 365 nm, λ_em = 530 nm), were first and simply synthesized by one-step hydrothermal treatment using ascorbic acid (AA) as a carbon source in alcohol–water binary systems. The two emitters could be easily separated through extraction with chloroform. A series of experiments demonstrated that the alcohol–water binary systems played a vital role in synthesis of DECNDs, and the dual emissions were ascribed to two types of carbon nanodots due to the different modified ligands on their surfaces, such as ascorbic acid capped on the blue emitters and alcohol molecules capped on the yellow emitters. By taking advantage of the unique dual-emission characteristic, some new applications were developed. For instance, on the basis of the independent responses of dual emissions to low pH values, the DECNDs could be used as a reliable and accurate pH sensor in acid medium, and both intensity of a single emission and intensity ratios of dual emissions could be employed to construct calibrations for pH measurement. Besides, the obtained DECNDs also exhibited excellent biocompatibility and low cytotoxicity, suggesting great potential for biomedical applications

Box-Behnken design and observed response.

<p>Box-Behnken design and observed response.</p

A novel and sensitive method for determining vitamin B3 and B7 by pre-column derivatization and high-performance liquid chromatography method with fluorescence detection - Fig 5

<p>The 3D response surface of peak area affected by varying derivatization temperature and time(a), varying derivatization temperature and EDC dosage (b), derivatization time and EDC dosage (c).</p

Linear range, correlation coefficient, precision, accuracy, quantitative limits, detection limits and repeatability.

<p>Linear range, correlation coefficient, precision, accuracy, quantitative limits, detection limits and repeatability.</p

Gas Purge Microextraction Coupled with Stable Isotope Labeling–Liquid Chromatography/Mass Spectrometry for the Analysis of Bromophenols in Aquatic Products

A green, sensitive, and accurate method was developed for the extraction and determination of bromophenols (BPs) from aquatic products by using organic solvent-free gas purge microsyringe extraction (GP–MSE) technique in combination with stable isotope labeling (SIL) strategy. BPs were extracted by NaHCO₃ buffer solution, with recoveries varying from 92.0% to 98.5%. The extracted solution was analyzed by SIL strategy, during which analytes and standards were labeled by 10-methyl-acridone-2-sulfonyl chloride (<i>d</i>₀-MASC) and its deuterated counterpart <i>d</i>₃-MASC, respectively. The labeling reaction was finished within 10 min with good stability. The liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) sensitivity of BPs was greatly enhanced due to the mass-enhancing property of MASC, while the matrix effect was effectively minimized by the SIL strategy. The limits of detection (LODs) were in the range of 0.10–0.30 μg/kg, while the limits of quantitations (LOQs) were in the range of 0.32–1.0 μg/kg. The proposed method also showed great potential in the qualitative analysis of other bromophenols in the absence of standard

The extraction process of tea samples.

<p>The extraction process of tea samples.</p

Estimated regression coefficients for the quadratic polynomial model and ANOVA for the experimental results in the optimization of flavonoids extractions.

<p>Estimated regression coefficients for the quadratic polynomial model and ANOVA for the experimental results in the optimization of flavonoids extractions.</p

Comparisons of the proposed method with previously reported methods.

<p>Comparisons of the proposed method with previously reported methods.</p