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1.
Bioelectrochemistry ; 121: 7-10, 2018 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-29306186

RESUMEN

A chitosan based hydrogel has been fabricated using silver ions as crosslinking agent. Silver redox behavior in the hydrogel is suppressed due to complexation. However, hydrogen peroxide induced hydroxyl radicals could attract the glucoside bonds and consequently restore silver redox behavior. Therefore, we used this hydroxyl radical induced chitos and epolymerization mechanism as an indicator for antioxidant capacity evaluation. Therefore, we used this hydroxyl radical induced chitos and epolymerization as an indicator for antioxidant capacity evaluation. Due to the low cost, portability and avoidance of the need for electrode modification, we believe the proposed hydrogel sensing platform shows great potential for antioxidant screening applications.


Asunto(s)
Antioxidantes/farmacología , Ácido Ascórbico/farmacología , Quitosano/química , Técnicas Electroquímicas/métodos , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Radical Hidroxilo/análisis , Evaluación Preclínica de Medicamentos/métodos , Oxidación-Reducción/efectos de los fármacos , Polimerizacion/efectos de los fármacos , Plata/química
2.
J Chromatogr A ; 1407: 42-51, 2015 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-26166295

RESUMEN

A new method for the determination of seven organophosphorus pesticides was developed using dynamic microwave-assisted extraction online coupled with single drop microextraction prior to gas chromatographic mass spectrometry (GC-MS). The method combines the advantages of dynamic microwave-assisted extraction and single-drop microextraction, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, tea samples were extracted with 25% ethanol aqueous solution and purified with acidic alumina at the same time, and then the analytes were concentrated into microextraction solvent. When the extraction was completed, the solvent microdrop containing the enriched analytes was retracted into the microsyringe and directly analyzed by GC-MS without any filtration or cleanup step. The method makes extraction, cleanup, separation, and enrichment to be carried out in one step. Several experimental parameters, including type of extraction solvent, type and amount of dispersant, type and volume of microextraction solvent, microwave power, extraction time, and flow rate of extraction solvent were investigated and optimized. Under optimal experimental conditions, good linearity was observed in the range of 2.00-500.00 µg kg(-1). The limits of detection and quantification were in the range of 0.4-1.7 µg kg(-1) and 1.1-5.6 µg kg(-1), respectively. The present method was applied to the analysis of tea samples, and the recoveries of analytes were in the range of 84.9-106.4% with the relative standard deviations ranging from 1.0 to 6.1%. The results showed that the present method was a rapid and feasible method for the determination of organophosphorus pesticides in tea samples.


Asunto(s)
Análisis de los Alimentos/métodos , Microondas , Plaguicidas/análisis , Té/química , Cromatografía de Gases y Espectrometría de Masas , Solventes/química , Contaminantes Químicos del Agua/análisis
3.
J Agric Food Chem ; 63(8): 2154-61, 2015 Mar 04.
Artículo en Inglés | MEDLINE | ID: mdl-25665636

RESUMEN

Dispersive microsolid-phase extraction based on metal-organic framework has been developed and applied to the extraction of triazine and phenylurea herbicides in vegetable oils in this work. The herbicides were directly extracted with MIL-101 from diluted vegetables oils without any further cleanup. The separation and determination of herbicides were carried out on high performance liquid chromatography. The effects of experimental parameters, including volume ratio of n-hexane to oil sample, mass of MIL-101, extraction time, centrifugation time, eluting solvent, and elution time were investigated. The Student's t test was applied to evaluate the selected experimental conditions. The limits of detection for the herbicides ranged from 0.585 to 1.04 µg/L. The recoveries of the herbicides ranged from 87.3 to 107%. Our results showed that the present method is rapid, simple, and effective for extracting herbicides in vegetable oils.


Asunto(s)
Complejos de Coordinación/química , Herbicidas/aislamiento & purificación , Compuestos de Fenilurea/aislamiento & purificación , Aceites de Plantas/química , Extracción en Fase Sólida/métodos , Triazinas/aislamiento & purificación , Contaminación de Alimentos/análisis , Herbicidas/análisis , Límite de Detección , Estructuras Metalorgánicas , Metales/química , Compuestos de Fenilurea/análisis , Extracción en Fase Sólida/instrumentación , Triazinas/análisis
4.
J Pharm Biomed Anal ; 104: 97-104, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25497891

RESUMEN

The ultrasound-assisted ionic liquid-based homogeneous liquid-liquid microextraction has been developed and applied to the extraction of four tanshinones, including dihydrotanshinone, tanshinone I, cryptotanshinone and tanshinone IIA in Salvia miltiorrhiza Bge. root. High performance liquid chromatography was applied to the separation and determination of the analytes. The ionic liquid was used as extraction solvent and target analytes were extracted with help of ultrasound. Then, ion-pairing agent was added into the sample solution, which resulted in the formation of water-insoluble ionic liquid in the solution. The phase separation was performed by centrifugation. The extraction, concentration and purification of target analytes were performed simultaneously. The experimental parameters, including type and volume of ionic liquid, sample amount, the size of sample particle, pH value of extraction medium, extraction temperature, extraction time, amount of ion-pairing agent and centrifuging time, were investigated and optimized. The calibration curves showed good linear relationship (r>0.9997). The limits of detection and quantification were in the range of 0.052-0.093 and 0.17-0.31 µg mL(-1), respectively. The recoveries were between 70.45% and 94.23% with relative standard deviations lower than 5.31%. The present method is free of volatile organic solvents, and represents lower expenditures of sample, extraction time and solvent, compared with UAE and HRE. There was no obvious difference in the extraction yields of active constitutions obtained by the three extraction methods.


Asunto(s)
Abietanos/análisis , Medicamentos Herbarios Chinos/análisis , Extractos Vegetales/química , Raíces de Plantas/química , Salvia miltiorrhiza/química , Cromatografía Líquida de Alta Presión/métodos , Microextracción en Fase Líquida/métodos , Fenantrenos/análisis , Ultrasonido/métodos
5.
J Sep Sci ; 36(14): 2348-57, 2013 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-23677705

RESUMEN

Nine nucleosides and nucleobases, including uracil, adenine, thymine, uridine, adenosine, thymidine, cytidine, guanosine, and cordycepin in natural Cordyceps sinensis, cultured Cordyceps mycelia, and Cordyceps fruiting bodies were extracted by matrix solid-phase dispersion (MSPD) and determined by HPLC. The experimental conditions for the MSPD extraction were optimized. Florisil was used as dispersant, petroleum ether as washing solvent, and methanol as elution solvent. The Florisil-to-sample ratio was selected to be 4:1 and no additional clean-up sorbent was needed. The calibration curves had good linear relationships (r > 0.9997). The LOD and LOQ were in the range of 12~79 and 41~265 ng/mL, respectively. The intra- and interday precision were lower than 8.3%. The recoveries were between 61.5 and 93.2%. The present method consumed less sample compared with ultrasonic extraction and heating reflux extraction (HRE). The extraction yields obtained by using the present method are much higher than those obtained by UE and comparable to those obtained by HRE.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Cordyceps/química , Nucleósidos/análisis , Nucleótidos/análisis , Extractos Vegetales/análisis , Extracción en Fase Sólida/métodos , Nucleósidos/aislamiento & purificación , Nucleótidos/aislamiento & purificación , Extractos Vegetales/aislamiento & purificación
6.
J Chromatogr B Analyt Technol Biomed Life Sci ; 879(30): 3423-8, 2011 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-21963478

RESUMEN

The organophosphorus pesticides including phorate, diazinon, tolclofos-methyl, fenitrothin, malathion, fenthion, isocarbophos, quinalphos and phenamiphos, in peanut oils were determined by liquid-liquid extraction coupled with dispersive solid phase extraction and gas chromatography-mass spectrometry (GC-MS). The mixture of multi-walled carbon nanotubes and alumina was used as adsorbent in dispersive solid phase extraction. The effects of some experimental conditions, such as types of multi-walled carbon nanotubes, amount of adsorbents and extraction time were examined. The limits of detection for the analytes were between 0.7 and 1.6 µg kg(-1). The obtained recoveries of the analytes in the samples were between 85.9 and 114.3% and relative standard deviations were lower than 8.48%.


Asunto(s)
Cromatografía de Gases y Espectrometría de Masas/métodos , Compuestos Organotiofosforados/análisis , Plaguicidas/análisis , Aceites de Plantas/química , Extracción en Fase Sólida/métodos , Arachis , Modelos Lineales , Nanotubos de Carbono/química , Compuestos Organotiofosforados/aislamiento & purificación , Aceite de Cacahuete , Plaguicidas/aislamiento & purificación , Aceites de Plantas/análisis , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
7.
J Sep Sci ; 34(9): 1069-75, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21416601

RESUMEN

Headspace single drop microextraction (HS-SDME) coupled with microwave extraction (ME) was developed and applied to the extraction of the essential oil from dried Syzygium aromaticum (L.) Merr. et Perry and Cuminum cyminum L. The operational parameters, such as microdrop volume, microwave absorption medium (MAM), extraction time, and microwave power were optimized. Ten microliters of decane was used as the microextraction solvent. Ionic liquid and carbonyl iron powder were used as MAM. The extraction time was less than 7 min at the microwave power of 440 W. The proposed method was compared with hydrodistillation (HD). There were no obvious differences in the constituents of essential oils obtained by the two methods.


Asunto(s)
Fraccionamiento Químico/métodos , Cuminum/química , Myrtaceae/química , Aceites Volátiles/aislamiento & purificación , Aceites de Plantas/aislamiento & purificación , Fraccionamiento Químico/instrumentación , Microondas , Aceites Volátiles/análisis
8.
J Chromatogr B Analyt Technol Biomed Life Sci ; 878(28): 2707-11, 2010 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-20810325

RESUMEN

The arctiin and arctigenin in the fruit of Arctium lappa L. were extracted by matrix solid-phase dispersion (MSPD) and determined by high-performance liquid chromatography (HPLC) with fluorescence detection. The experimental conditions for the MSPD were optimized. Silica gel was selected as dispersion adsorbent and methanol as elution solvent. The calibration curve showed good relationship (r>0.9998) in the concentration range of 0.010-5.0µgmL(-1) for arctiin and 0.025-7.5µgmL(-1) for arctigenin. The recoveries were between 74.4% and 100%. The proposed method consumed less sample, time and solvent compared with conventional methods, including ultrasonic and Soxhlet extraction.


Asunto(s)
Arctium/química , Cromatografía Líquida de Alta Presión/métodos , Medicamentos Herbarios Chinos/química , Frutas/química , Furanos/análisis , Glucósidos/análisis , Lignanos/análisis , Extracción en Fase Sólida/métodos , Adsorción , Furanos/química , Glucósidos/química , Lignanos/química , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Espectrometría de Fluorescencia
9.
J Chromatogr A ; 1217(12): 1875-81, 2010 Mar 19.
Artículo en Inglés | MEDLINE | ID: mdl-20138285

RESUMEN

An on-line method, based on coupling dynamic ultrasonic extraction (DUE), continuously sampling the suspension of sample and solvent, high performance liquid chromatographic separation with diode array detection, has been developed for the determination of the flavonoids, including baicalin, baicalein and wogonin, from the root of Scutellaria baicalensis Georgi. Variables influencing the DUE were evaluated by orthogonal test. The extraction yields of baicalin, baicalein and wogonin in the roots of S. baicalensis Georgi obtained from five different cultivated areas are 73.8-131.5 microg mg(-1) (RSD< or =6.24%), 6.8-15.9 microg mg(-1) (RSD< or =5.36%) and 4.4-14.3 microg mg(-1) (RSD< or =5.30%), respectively. The limits of detection for baicalin, baicalein and wogonin are 0.30, 0.37 and 0.41 microg mL(-1), respectively. Linearity is from 0.55 to 109 microg mL(-1) for baicalin, from 0.51 to 105 microg mL(-1) for baicalein and from 0.53 to 102 microg mL(-1) for wogonin. Compared with off-line continuous flow-DUE, the proposed method would be more convenient for the determination of the analytes and the rapid optimization of the extraction process. The extraction yields of flavonoids obtained by the proposed method are comparable with those obtained by dynamic microwave assisted extraction, static ultrasonic extraction and reflux extraction. The result indicated that the proposed method is suitable to determine the active components in Chinese herbal medicine.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Flavonoides/análisis , Sistemas en Línea , Raíces de Plantas/química , Reología/métodos , Scutellaria baicalensis/química , Ultrasonido , Estudios de Evaluación como Asunto , Flavanonas/análisis , Flavanonas/química , Flavonoides/química , Límite de Detección , Tamaño de la Partícula , Estándares de Referencia , Análisis de Regresión , Solventes
10.
J Sep Sci ; 32(20): 3544-9, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19764052

RESUMEN

Ionic liquid was used as microwave absorption medium and applied to the extraction of essential oils from dried fruits of the Illicium verum Hook. f. and Cuminum cyminum L. by microwave-assisted extraction. The extraction time is less than 15 min at the microwave power of 440 W. The constituents of essential oils obtained by the proposed method were compared with those obtained by hydrodistillation. There is no obvious difference in the constituents of essential oils obtained by the two methods.


Asunto(s)
Cuminum/química , Illicium/química , Líquidos Iónicos/química , Microondas , Aceites Volátiles/aislamiento & purificación , Aceites de Plantas/aislamiento & purificación , Absorción , Cromatografía de Gases y Espectrometría de Masas , Extractos Vegetales/química
11.
Anal Chim Acta ; 596(1): 164-70, 2007 Jul 16.
Artículo en Inglés | MEDLINE | ID: mdl-17616254

RESUMEN

This paper describes a new method for the determination of total flavonoids in Platycladus orientalis (L.) Franco. The method was based on dynamic microwave-assisted extraction (DMAE) coupled with on-line derivatization and ultraviolet-visible (UV-vis) detection. The influence of the experimental conditions was tested. Maximum extraction yield was achieved using 80% aqueous methanol of extraction solvent; 80 W of microwave output power; 5 min of extraction time; 1.0 mL min(-1) of extraction solvent flow rate. The derivatization reaction between aluminium chloride and flavonoid is one of the most sensitive and selective reactions for total flavonoids determination. The optimized derivatization conditions are as follows: derivatization reagent 1.5% aluminium chloride methanol solution; reaction coil length 100 cm; derivatization reagent flow rate 1.5 mL min(-1). The detection and quantification limits obtained are 0.28 and 0.92 mg g(-1), respectively. The intra-day and inter-day precisions (R.S.D.) obtained are 1.5% and 4.6%, respectively. Mean recovery is 98.5%. This method was successfully applied to the determination of total flavonoids in P. orientalis (L.) Franco and compared with heat reflux extraction. The results showed that the higher extraction yield of total flavonoids was obtained by DMAE with shorter extraction time (5 min) and small quantity of extraction solvent (5 mL).


Asunto(s)
Cupressaceae/química , Flavonoides/análisis , Microondas , Sistemas en Línea , Espectrofotometría Ultravioleta/métodos , Cloruro de Aluminio , Compuestos de Aluminio/química , Cloruros/química , Metanol/química , Estructura Molecular , Extractos Vegetales/química , Sensibilidad y Especificidad , Soluciones/química
12.
Talanta ; 74(1): 146-52, 2007 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-18371624

RESUMEN

The high-performance liquid chromatography (HPLC) coupled with on-line solid phase extraction (SPE) and ultraviolet (UV) detection was developed for determining andrographolide and dehydroandrographolide in rabbit plasma. Plasma samples (100 microL) were injected directly into a C18 SPE column and the biological matrix was washed out for 6 min using 15% aqueous methanol. By rotation of the switching valve, andrographolide and dehydroandrographolide were eluted in the back-flush mode and transferred to the analytical column by the chromatographic mobile phase consisted of methanol:acetonitrile (ACN):water (50:10:40; v/v). The UV detection was performed at 225 nm. The calibration curves showed excellent linear relationship (R> or =0.9993) over the concentration range of 0.05-5.0 microg mL(-1). The within- and between-day precisions (R.S.D.) of two analytes were in the range of 1.2-6.5% and the accuracies were between 92.0% and 102.1%. Their recoveries were all greater than 94%. The limits of detection were 0.019 microg mL(-1) for andrographolide and 0.022 microg mL(-1) for dehydroandrographolide. This method was successfully applied to the plasma concentration-time curve study after oral administration of Andrographis paniculata Nees extract in rabbit.


Asunto(s)
Andrographis/química , Diterpenos/sangre , Extractos Vegetales/farmacocinética , Animales , Cromatografía Líquida de Alta Presión , Femenino , Masculino , Sistemas en Línea , Conejos , Reproducibilidad de los Resultados , Extracción en Fase Sólida
13.
Anal Bioanal Chem ; 386(6): 1863-8, 2006 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17047940

RESUMEN

A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.


Asunto(s)
Illicium/química , Microondas , Aceites Volátiles/análisis , Aceites Volátiles/química , Zingiber officinale/química , Adsorción , Carbono , Grafito , Calor , Compuestos de Hierro , Extractos Vegetales/análisis , Extractos Vegetales/química , Solventes , Factores de Tiempo , Agua
14.
J Pharm Biomed Anal ; 32(3): 479-85, 2003 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-14565552

RESUMEN

In this paper, a novel method to separate and determine oleanolic acid and ursolic acid isomers in Ligustrum lucidum Ait was studied by micellar electrokinetic capillary chromatography (MECC). The baseline separation of the two analytes were obtained on the condition that the buffer contained 15 mmol/l disodium hydrogen phosphate, 15 mmol/l disodium tetreborate, 10 mmol/l SDS and 5% (v/v) alcohol. The contents of the oleanolic acid and ursolic acid were determined in L. lucidum Ait, Folium photiniae and Flos campsis; they were 78.3 (R.S.D. = 2.75%) and 20.7 mg/g (R.S.D. = 2.97%), 27.9 (R.S.D. = 3.67%) and 79.8 mg/g (R.S.D. = 3.44%), 65.5 (R.S.D. = 3.73%) and 60.4 mg/g (R.S.D. = 4.06%) (n = 5), respectively. The recoveries of the analytes in the extract of L. lucidum Ait were 102%, (R.S.D. = 2.85%) for oleanolic acid and 104% (R.S.D. = 3.21%) for ursolic acid (n = 5). With the emphasis on the effects of SDS and alcohol concentrations on the separation of the isomers were investigated.


Asunto(s)
Ligustrum/química , Ácido Oleanólico/análisis , Triterpenos/análisis , Algoritmos , Cromatografía Líquida de Alta Presión , Cromatografía Capilar Electrocinética Micelar , Indicadores y Reactivos , Extractos Vegetales/análisis , Control de Calidad , Reproducibilidad de los Resultados , Dodecil Sulfato de Sodio , Espectrofotometría Ultravioleta , Ácido Ursólico
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