Wan Cao

Trace-chitosan-wrapped multi-walled carbon nanotubes as a new sorbent in dispersive micro solid-phase extraction to determine phenolic compounds.

This report describes the use of trace-chitosan-wrapped multi-walled carbon nanotubes (CS-MWCNTs) as a sorbent material in dispersive micro solid-phase extraction (DMSPE), which was combined with ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry to analyze phenolic compounds in chrysanthemum tea and a chrysanthemum beverage. In this study, for the first time, CS-MWCNTs were used as a sorbent for this microextraction mode. Moreover, the proposed method exhibits the advantages of simplicity, rapidity, small sample amount and ease of operation. Furthermore, all of the important parameters that affect the extraction efficiency, such as the sorbent, pH, extraction time and type of elution solvent, were investigated and optimized in the DMSPE. Under the optimized extraction condition, the limit of detection, which was calculated based on a signal-to-noise ratio of 3, was 0.22-16.19ngmL(-1). Satisfactory recovery values of 89-106% were obtained for the tested samples. The results show that the developed method was successfully applied to determine the content of chlorogenic acid and flavonoids in complex chrysanthemum samples.

Determination of Tetracycline Antibiotic Residues in Honey and Milk by Miniaturized Solid Phase Extraction Using Chitosan-Modified Graphitized Multiwalled Carbon Nanotubes

A rapid, simple, and strongly selective miniaturized solid phase extraction (SPE) technique, requiring only small amounts of sorbent (24 mg) and elution solvent (600 μL), coupled with ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry was developed for detecting tetracycline antibiotics. These analytes were extracted from honey and milk using chitosan-modified graphitized multiwalled carbon nanotubes (G-MWNTs) as the solid sorbent and acetonitrile/acetic acid (8:2, v/v) as the eluent in miniaturized SPE. Under the optimum experimental conditions, a satisfactory linearity (r(2) > 0.992) was obtained, and the limits of detection were in the range of 0.61-10.34 μg/kg for the analytes. The mean recoveries of the five tetracycline antibiotic residues in the real samples were between 81.5 and 101.4%. The results demonstrated that chitosan-modified G-MWNTs comprise a promising material for the enrichment of tetracycline antibiotics from complex food matrices.

Application of ionic liquids for elution of bioactive flavonoid glycosides from lime fruit by miniaturized matrix solid-phase dispersion

In this work, two flavonoid glycosides (neohesperidin and naringin) in lime fruit were effectively extracted by miniaturized matrix solid phase dispersion (MSPD), followed by ultra-performance liquid chromatography-ultraviolet detection. The best results were obtained using Florisil (150mg) as the sorbent and 1-butyl-3-methylimidazolium tetrafluoroborate (0.4mL, 250mM) as the elution solvent. This work represents the first attempt of using ionic liquids as a green eluent for extraction of the investigated compounds in miniaturized MSPD. Compared with the conventional methods, the proposed method is advantageous due to improved enrichment factor and reduced reagent consumption. A good linearity was observed with r(2) values (>0.998). Meanwhile, the method gave acceptable recoveries (90.16-96.47%) for the determination of flavonoids in plant samples. The limits of detection of the two analytes ranged between 4.08 and 5.04μg/g. The results showed that the optimized method has a great potential for sample preparation in routine analysis of complex plant samples.

Trace matrix solid phase dispersion using a molecular sieve as the sorbent for the determination of flavonoids in fruit peels by ultra-performance liquid chromatography

A simple, rapid, and highly selective trace matrix solid phase dispersion (MSPD) technique, coupled with ultra-performance liquid chromatography-ultraviolet detection, was proposed for extracting flavonoids from orange fruit peel matrices. Molecular sieve SBA-15 was applied for the first time as a solid support in trace MSPD. Parameters, such as the type of dispersant, mass ratio of the sample to the dispersant, grinding time, and elution pH, were optimized in detail. The optimal extraction conditions involved dispersing a powdered fruit peel sample (25 mg) into 25mg of SBA-15 and then eluting the target analytes with 500 μL of methanol. A satisfactory linearity (r(2) > 0.9990) was obtained, and the calculated limits of detection reached 0.02-0.03 μg/mL for the compounds. The results showed that the method developed was successfully applied to determine the content of flavonoids in complex fruit peel matrices.

Quantitative analysis of flavanones from citrus fruits by using mesoporous molecular sieve-based miniaturized solid phase extraction coupled to ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry

An analytical procedure based on miniaturized solid phase extraction (SPE) and ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was developed and validated for determination of six flavanones in Citrus fruits. The mesoporous molecular sieve SBA-15 as a solid sorbent was characterised by Fourier transform-infrared spectroscopy and scanning electron microscopy. Additionally, compared with reported extraction techniques, the mesoporous SBA-15 based SPE method possessed the advantages of shorter analysis time and higher sensitivity. Furthermore, considering the different nature of the tested compounds, all of the parameters, including the SBA-15 amount, solution pH, elution solvent, and the sorbent type, were investigated in detail. Under the optimum condition, the instrumental detection and quantitation limits calculated were less than 4.26 and 14.29ngmL(-1), respectively. The recoveries obtained for all the analytes were ranging from 89.22% to 103.46%. The experimental results suggested that SBA-15 was a promising material for the purification and enrichment of target flavanones from complex citrus fruit samples.

Ultramicro chitosan-assisted in-syringe dispersive micro-solid-phase extraction for flavonols from healthcare tea by ultra-high performance liquid chromatography

A novel dispersive micro-solid-phase extraction (DMSPE) method using ultramicro chitosan as an adsorbent was proposed for the analysis of flavonols in Flos Sophorae tea, with detection by ultra-high performance liquid chromatography. Various parameters affecting the extraction recovery, including the concentration and viscosity of chitosan, extraction time and the pH of the sample solution were investigated and optimized. The optimized conditions were found to be 0.4μg/mL of sorbent, pH of 7, an extraction time of 1.0min and 100μL of methanol as the elution solvent. The DMSPE method showed excellent linearity (r(2)>0.99) with pre-concentration factor values ranging from 23 to 77-fold. The limits of detection and quantification were 0.22-0.36ng/mL and 0.72-1.21ng/mL, respectively. This method was successfully applied to the analysis of flavonols in Flos Sophorae tea samples, and their recoveries were in the range of 95.2-102.4%.

Highly sensitive analysis of flavonoids by zwitterionic microemulsion electrokinetic chromatography coupled with light-emitting diode-induced fluorescence detection

A rapid zwitterionic microemulsion electrokinetic chromatography (ZI-MEEKC) approach coupled with light-emitting-diode-induced fluorescence (LED-IF, 480nm) detection was proposed for the analysis of flavonoids. In the optimization process, we systematically investigated the separation conditions, including the surfactants, cosurfactants, pH, buffers and fluorescence parameters. It was found that the baseline separation of the seven flavonoids was obtained in less than 5min with a running buffer consisting of 92.9% (v/v) 5mM sodium borate, 0.6% (w/v) ZI surfactant, 0.5% (w/v) ethyl acetate and 6.0% (w/v) 1-butanol. High sensitivity was obtained by the application of LED-IF detection. The limits of detection for seven flavonoids were in the range of 3.30×10(-8) to 2.15×10(-6)molL(-1) without derivatization. Ultimately, the detection method was successfully applied to the analysis of flavonoids in hawthorn plant and food products with satisfactory results.

Ionic Liquid-Based One-Step Micellar Extraction of Multiclass Polar Compounds from Hawthorn Fruits by Ultrahigh-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry

An ionic liquid (IL)-based one-step micellar extraction procedure was developed for the extraction of multiclass polar analytes (protocatechuic acid, chlorogenic acid, epicatechin, hyperoside, isoquercitrin, quercetin) from hawthorn fruits and their determination using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS). Compared to conventional organic solvent extractions, this newly proposed method was much easier, more sensitive, environmentally friendly, and effective as well. Several important parameters influencing the micellar extraction efficiency are discussed, such as selection of ILs, surfactant concentration, and extraction time. Under the optimal conditions, good linearity was achieved for each analyte with correlation coefficients (r(2)) ranging from 0.9934 to 0.9999, and the recovery values ranged from 89.3 to 106% with relative standard deviations lower than 5.5%. Results suggest that the IL-based one-step micellar extraction could be an alternative and promising means in future food analysis.

Dispersive Micro-Solid-Phase Extraction Using Mesoporous Hybrid Materials for Simultaneous Determination of Semivolatile Compounds from Plant Tea by Ultra-High-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry

This report described the use of mesoporous hybrid materials (MHM) in a dispersive micro-solid-phase extraction procedure to extract semivolatile compounds from plant tea that were then analyzed by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. Dihydrotanshinone I, tanshinone I, cryptotanshinone, and tanshinone IIA were selected as the model compounds, and the extraction parameters, including mesoporous concentration, extraction time, sample agitation and desorption solvents, were optimized. The interaction with the analytes and the large surface area of the MHM facilitated the adsorption of analytes. The method showed good linearity, with correlation coefficients >0.9980 in the range 0.25-100 ng/mL, and low limits of detection (0.012-0.046 pg). Finally, the recovery values were 91-103% for Danshen tea, 89-102% for Danshen, and 88-96% for tanshinone capsules. The results showed that the proposed method was suitable for the extraction and determination of tanshinones in complex samples.

Ionic-Liquid-Micelle-Functionalized Mesoporous Fe3O4 Microspheres for Ultraperformance Liquid Chromatography Determination of Anthraquinones in Dietary Supplements

A magnetic solid-phase extraction method using ionic liquid (IL)-micelle-functionalized mesoporous Fe3O4 microspheres (MFMs) was proposed for the preconcentration of anthraquinones in dietary supplements. The analytes were then determined by ultraperformance liquid chromatography combined with an ultraviolet detector. The extraction parameters, such as the choice of ILs, the concentrations of ILs and MFMs, the pH of diluent, and the concentration of acetic acid in the eluent, were presented. Under the optimized conditions, the limits of detection and limits of quantitation were 0.4-2.8 ng mL(-1) and 1.4-9.4 ng mL(-1), respectively. The accuracy of the proposed method was investigated by recovery in herb and granules of Radix et Rhizoma Rhei, yielding values between 89.25% and 96.48%. The use of the proposed method in the sample pretreatment of complex dietary supplements is feasible due to the high surface area and excellent adsorption capacity of MFMs after modification with IL.