Deep eutectic solvents used as extraction solvent for the determination of flavonoids from Camellia oleifera flowers by high-performance liquid chromatography.

INTRODUCTION: Camellia oleifera flowers are rich in flavonoids, but there has been little attention on their application. A simple and reliable method for determining the content of flavonoids in C. oleifera flowers would be very helpful for the utilisation of agriculture resources. OBJECTIVE: To develop an efficient analytical method for the determination of flavonoids in C. oleifera flowers by high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. METHODOLOGY: Preparing an environmentally-friendly and effective solvent - deep eutectic solvents (DESs) - for compound extraction. Then investigating the influential factors of ultrasound-assisted extraction with DESs by the Box-Behnken design combined with response surface methodology. RESULTS: DES-5 synthesised with choline chloride and lactic acid (1:2) acquired excellent extractability for four flavonoids (quercetin 3-O-rhamnoside, kaempferol 3-O-rhamnoside and their aglycones) with different polarity. The proposed method, which could simultaneously determine four flavonoids with HPLC-UV detection for the first time, displays satisfactory recovery yields and high precision with inter-day relative standard deviation lower than 5.80%. CONCLUSION: DESs could be promising solvents for efficiently and selectively extracting bioactive compounds from plant materials, and the analytical method for flavonoids of C. oleifera flowers could provide reference value for its application and be used in other plant resources.

A convenient and effective method for determining organophosphorus pesticides in citrus fruits based on a novel dispersive solid phase extraction using UiO-66/Alg bead as the sorbent.

This work presents a novel, convenient and effective method for assaying organophosphorus pesticides (OPPs) in the pulp and peel of citrus fruits. In this method, shaped UiO-66/alginate (UiO-66/Alg) beads were employed to replace the powder sorbents used in traditional dispersive solid phase extraction (d-SPE) methods. The UiO-66/Alg beads can be easily separated by only using a tweezer within 1 min, which effectively simplifies the sample pretreatment and overcomes the shortages brought by the incomplete separation of powder sorbents. Moreover, the matrix compounds can be effectively excluded by UiO-66/Alg beads, and the UiO-66/Alg beads can be reused at least 8 times. The d-SPE conditions were optimized by a single factor test. The method shows satisfactory sensitivity, accuracy and precision. Furthermore, ATR-FTIR and UV-Vis-DRS were employed to investigate the adsorption mechanism. Finally, the developed method was applied to monitor the OPPs in ten different citrus fruits.

Synergistic promotion of nitrogen vacancies and single atomic dopants on Pt/C3N4 for photocatalytic hydrogen evolution.

C3N4 is widely applied in the synthesis of single-atom catalysts. However, understanding on the active site and the reaction mechanism is not fully in consensus. Especially, bare studies have considered the coordination environment of the single-atomic dopant and the effect of nitrogen vacancy on C3N4. In this study, we found that the presence of nitrogen vacancies promotes the activation of water and reduces the activation energy barrier for hydrogen generation. The results show that a synergistic effect between single-atom Pt and nitrogen vacancies enables the catalyst to achieve a superior hydrogen production rate of 3,890 µmol/g/h, which is 16.8 times higher than that of pristine C3N4. Moreover, the catalyst is also applicable for photocatalytic hydrogen production from seawater without significantly decreased hydrogen production rate. This study paves the way for the rational design and optimization of next-generation photocatalysts for sustainable energy applications, particularly in solar-driven hydrogen production.

A simplified dispersive solid-phase extraction using a shaped zirconium-based metal-organic framework: Constructing a novel, facile and efficient method for detecting plant growth regulators in citrus fruits.

A facile, efficient and reliable method was designed and established to analyze the plant growth regulators (PGRs) in citrus fruit, based on a simplified dispersive solid-phase extraction (d-SPE) using a shaped zirconium-based metal-organic framework (UiO-66-PDMS bead) as the sorbent. In this method, UiO-66-PDMS beads directly extracted the targets from the homogenized and could be easily separated with a tweezer. It avoided the centrifugation or filtration operation required in normal d-SPE, greatly simplifying the d-SPE process. Moreover, the matrix substances were efficiently removed by this d-SPE process. The method showed good linearities (R2 ≥ 0.9995) and limits of detection (0.09-0.17 ng/g). The recoveries were in the range of 80.7-97.5 %. The intra-day and inter-day precisions were 1.5-6.3 % and 4.6-11.7 %, respectively. Additionally, the adsorption interactions between UiO-66-PDMS bead and PGRs were studied by ATR-FTIR and UV-vis DRS. Furthermore, the method was employed to screen the PGRs in ten different citrus fruits.

Investigation on the Contents of Nε-carboxymethyllysine, Nε-carboxyethyllysine, and N-nitrosamines in Commercial Sausages on the Chinese Market.

Sausages are among the most popular meat products worldwide. However, some harmful products, such as advanced glycation end-products (AGEs) and N-nitrosamines (NAs), can be formed simultaneously during sausage processing. In this study, the contents of AGEs, NAs, α-dicarbonyls and the proximate composition were investigated in two kinds of commercial sausages (fermented sausages and cooked sausages) in the Chinese market. The correlations among them were further analyzed. The results showed that the fermented and cooked sausages had different in protein/fat contents and pH/thiobarbituric acid reactive substance values due to their different processing technologies and added ingredients. The Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) concentrations varied from 3.67 to 46.11 mg/kg and from 5.89 to 52.32 mg/kg, respectively, and the NAs concentrations ranged from 1.35 to 15.88 µg/kg. The contents of some hazardous compounds, such as CML, N-nitrosodimethylamine, and N-nitrosopiperidine, were observed to be higher in the fermented sausages than in the cooked sausages. Moreover, levels of NAs in some sausage samples exceeded the limit of 10 µg/kg issued by the United States Department of Agriculture, suggesting that particular attention should be paid to mitigating NAs, especially in fermented sausages. The correlation analysis suggested that the levels of AGEs and NAs were not significantly correlated in both kinds of sausages.

Thermosensitive and magnetic molecularly imprinted polymers for selective recognition and extraction of aristolochic acid I.

Recently, the natural compound of aristolochic acid I (AAI) has attracted wide attentions due to its strong nephrotoxicity and carcinogenicity. However, the extraction of AAI based on conventional molecularly imprinted polymers (MIPs) are tedious with extensive eluent, causing secondary pollution and poor regeneration. Herein, thermosensitive and magnetic MIPs (TMMIPs) were synthesized by a surface imprinting method, which achieved thermosensitive capture/release of AAI, along with rapid magnetic separation, significantly shortening the elution time and reducing organic-solvent consumption. TMMIPs with dual-stimuli responses exhibited superior affinity, selectivity, kinetics, and regeneration ability towards AAI. TMMIPs were applied to analyze AAI in Houttuynia cordata via dispersive solid-phase extraction (d-SPE) coupled with high performance liquid chromatography (HPLC), yielding satisfactory recoveries (79.03-99.67%) and relative standard deviations (≤5.78%). The limit of detection of AAI was as low as 26.67 µg/L. TMMIPs demonstrate great applicability for fast, selective and eco-friendly extraction of AAI in complicated matrices.

[Analysis of fatty acids in leaves of Loropetalum chinense and L. chinense var. rubrum by GC-MS].

OBJECTIVE: To extract and analyze fatty acids in leaves of L. chinense Oliver and L. chinense var. rubrum Yieh. METHODS: The fatty acids were extracted with Soxhlet extractor and identified by the GC-MS method. RESULTS: 31, 26 and 30 components were identified from the leaves of L. chinense, the green leaves and red leaves of L. chinense var. rubrum. There were 19, 14 and 16 kinds of fatty acid in the respective leaves, which accounted for 99.09%, 95.31% and 98.83% of the total extraction, respectively. The main components in the extraction were oleic acid (30.77%, 47.01%, 75.28%), linoleic acid (48.49%, 29.26%, 0%), hexadecanoic acid (9.83%, 8.87%, 11.71%), octadecanoic acid (3.86%, 3.18%, 4.88%) and docosanoic acid (2.37%, 2.17%, 2.58%). CONCLUSION: Many kinds of unsaturated fatty acids exist in leaves of L. chinense Oliver and L. chinense var. rubrum Yieh. The leaves of these two plants can be used as the traditional Chinese medicine.

Simultaneous determination of organophosphorus pesticides in Chinese herbal medicines by microwave-assisted extraction coupled with dispersive-solid phase extraction and gas chromatography.

A reliable, rapid and nontoxic analytical method was proposed for the simultaneous determination of 16 organophosphorus pesticides in Chinese herbal medicines. The pesticides were extracted by ethanol and the experimental variables, such as temperature, extraction time and volume of ethanol, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-flame photometric detection. Under optimized conditions the obtained recoveries, except for isocarbophos, were in the range 73.8-123%, with relative standard deviations equal to or lower than 15.2% and limits of detection ranging from 0.001 to 0.009 mg/kg.

Fractionation, structure and conformation characterization of polysaccharides from Anoectochilus roxburghii.

Two new isolated polysaccharides, ARPP-40 (40 % ethanol precipitate) and ARPP-70 (70 % ethanol precipitate), were extracted from Anoectochilus roxburghii. The physicochemical properties of two polysaccharides were analyzed and the results showed the relative weight average molecular weights and contents of neutral sugar for ARPP-40 and ARPP-70 were 423 kDa and 97.4 %, 10.8 kDa and 51.4 %, respectively. In terms of monosaccharide composition, ARPP-40 contained only glucose, while ARPP-70 was composed of seven monosaccharides, of which glucose and galactose were the main components. Furthermore, the structure and conformation characteristics of ARPP-40 were systematically investigated. The results revealed that ARPP-40 was supposed to be a glucan and existed as a flexible chain with a polydispersity index of 1.02 in 0.1 M NaNO3 solution. The systematic information on structural and conformational properties of ARPP-40 was meaningful for its further application in food and medicinal industry.

Dispersive Solid-Phase Extraction Using Microporous Sorbent UiO-66 Coupled to Gas Chromatography-Tandem Mass Spectrometry: A QuEChERS-Type Method for the Determination of Organophosphorus Pesticide Residues in Edible Vegetable Oils without Matrix Interference.

A QuEChERS-type method without matrix interference was designed and developed to determine organophosphorus pesticide residues in edible vegetable oils, based on dispersive solid-phase extraction with cleanup using UiO-66 as sorbent. Microporous UiO-66 directly and selectively adsorbed organophosphorus pesticides and excluded interfering compounds. Clean analytes were obtained by elution and analyzed using gas chromatography-tandem mass spectrometry. The dispersive solid-phase extraction conditions (amount of adsorbent, extraction time, desorption solvent volume, and elution time) were optimized. The limits of detection of the pesticides in vegetable oils were 0.16-1.56 ng/g. Under optimized conditions, the average pesticide recoveries were 81.1-113.5%. The intraday and interday relative standard deviations for analyte recovery were <8.2 and <13.9%, respectively. Thus, the method is reliable and could detect organophosphorus pesticide residues in edible vegetable oils. Furthermore, UiO-66 can be easily recycled and reused at least 10 times, reducing the cost of analysis.

[Simultaneous analysis of multi-elements in vegetation oils by inductively coupled plasma atomic emission spectrometry].

A simple, accurate and sensitive method for the simultaneous analysis of eleven trace elements (Fe, Cu, Co, Ni, Pb, Al, Zn, Cd, Cr, Mn and Mg) in vegetation oils by ICP-AES has been developed. The oils were digested by H2 SO4 ashing method. The detection limits (MDLs) of the method for the eleven elements were in the range of 0.1-3.6 microg x kg(-1). The average recoveries at three concentrations of 0.1, 0.5 mg x kg(-1) were between 70.4% and 113% with the RSD in the range of 1.01%-10.6%. The proposed method has been applied to the determination of the above elements in soy, peanut, sesame, rape, tea and blended oils with satisfactory results.

Simultaneous determination of organophosphorus, organochlorine, pyrethriod and carbamate pesticides in Radix astragali by microwave-assisted extraction/dispersive-solid phase extraction coupled with GC-MS.

A simple, rapid and reliable method was proposed for the simultaneous determination of 27 pesticides (organophosphorus, organochlorine, pyrethroid and carbamate pesticides) in Radix astragali. The pesticides were extracted by acetonitrile and the experimental variables, such as temperature, extraction time and volume of acetonitrile, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine (PSA) as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-mass spectrometry in selected ion monitoring mode (GC-MS, SIM). The linearity of the calibration curves is good in matrix-matched standard, and yields the coefficients of determination (R(2))≥0.99 for approximately 96% of the target analytes. Under optimized conditions, the average recoveries (six replicates) for most pesticides (spiked at 0.02, 0.1 and 0.2 mg kg(-1)) range from 70% to 120%, and RSDs are less than 17.2%.

[Determination of isoxanthopterin in human urine by solid phase extraction-high performance anion-exchange chromatography coupled with integrated pulsed amperometric detection].

A sensitive, selective and environmental friendly method for the determination of isoxanthopterin in human urine by solid phase extraction (SPE)-high performance anion exchange chromatography (HPAEC) with integrated pulsed amperometric detector has been developed. The tandem solid phase extraction was employed to purify isoxanthopterin from human urine. The separation of isoxanthopterin was carried out on an IonPac AS21 anion-exchange column with eluent of 0.025 mol/L NaOH at the flow rate of 0.40 mL/min. Under the optimized conditions, the detection limit for isoxanthopterin was 0.003 mg/L, and the linear range was 0.005-0.200 mg/L. The spiked recoveries ranging from 95.4% to 96.8% were obtained in the urine samples from healthy persons and cancer patients, and the relative standard deviation (RSD) was less than 5%. The present method was successfully applied to the determination of isoxanthopterin in urine from healthy individuals and cancer patients.

Simultaneous determination of five synthetic antioxidants in edible vegetable oil by GC-MS.

A simple, quick and nontoxic analytical method for the simultaneous determination of five synthetic antioxidants [t-butyl-4-hydroxyanisole (BHA), 2,6-di-t-butyl-hydroxytoluene (BHT), t-butyl hydroquinone (TBHQ), ethoxyquin (EQ) and 2,6-di-tert-butyl-4-hydroxymethyl-phenol (Ionox 100)] in edible vegetable oil has been developed. The analytes were extracted by ethanol, then separated and detected by GC-MS. Extraction conditions such as volume of ethanol required, mixing time and number of extractions were investigated and optimized by an orthogonal array experimental design. The five compounds behaved linearly in the 0.100 approximately 20.0 mg/L concentration range, and the limits of detection (LOD) for BHA, BHT, TBHQ, EQ and Ionox-100 were 1.00, 0.92, 11.5, 0.83 and 1.39 microg/L, respectively. The recoveries at the tested concentrations of 1.00, 20.0 and 100 mg/kg were 75.6 approximately 123%, with coefficients of variation<10.0%. The proposed procedure was successfully applied to the simultaneous analysis of the five antioxidants in soybean oil, tea oil, edible blended oil, rap oil, peanut oil, peanut blended oil and sesame oil samples purchased from local supermarkets.