最新刊期
卷 30 ， 期 3 ， 2011
- 摘要：A new combination system of thermogravimetry-solid phase microextraction/gas chromatography-mass spectrometry(TG-SPME／GC-MS) was applied for analysis of the thermal properties of the glucose/asparagine model system nonaqueous phase Maillard reaction.46 main pyrolysis evolved products were identified and the dynamic changes of relative content of these products were monitored.The heating rate and air flow was set at 10 ℃/min and 400 mL/min,respectively.The evolved components were extracted with solid phase microextraction in the temperature range of 50-400 ℃.A continuous sampling method was adopted at different temperature section according to the results of TG/DTA.There were 5 temperature zones in whole reaction process.Additionally,the extract was separated and analyzed by GC-MS.The results showed that the whole thermo decomposition procedure of glucose/asparagine could be divided into four stages.A lot of volatile flavor compounds produced in these stages.The reaction was an endothermonic process.The thermolysis activation energy of glucose and asparagine,respectively，was higher than that of their mixed counter parts.There were 43 chromatographic peaks to be detected.Category and quantity of Maillard reaction product changed following the rise of temperature.In the low temperature section,long chain alkane,ketone and furfural were found.In the high temperature section,pyridine,pyrrole,imidazole and other heterocyclic compounds which contain N atom were detected.Adding vitamin C and ferulaic acid is an effective method to reduce acrylamide in glucose / asparagine model system nonaqueous phase Maillard reaction,and vitamin C on inhibition of acrylamide formation is more efficient than feruliac acid.关键词：solid phase microextraction;evolved species;glucose;asparagine;nonaqueous phase Maillard reaction
- 2120
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- 891
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- 4
发布时间： - 摘要：The content of oleuropein was usually determined by high performance liquid chromatography（HPLC） or gas chromatography（GC） method in previous studies.In this paper,a method for the determination of oleuropein in Olea europaea L.leaves was developed using a substraction of UV-Visible spectroscopy.With the standard rutin and oleuropein,two coloration systems including NaNO2-Al（NO3）3-NaOH and AlCl3 were both used.The total absorbance of total flavonoids and oleuropein was obtained at a wavelength of 510 nm in the former coloration system.In the latter coloration system,the absorbance of total flavonoid was obtained at a wavelength of 415 nm,but oleuropein was not detected at 415 nm in this system.According to the above absorbance properties,the content of oleuropein could be indirectly learned by substraction of the absorbances obtained in the two coloration systems.By using the developed UV-Vis method,the average contents of oleuropein in the olive leaves and purified extractums were 11.6% and 63.4% with RSDs（n=3）of 1.5% and 12%,respectively.Compared with the content determined by HPLC method,the relative error of this method was less than 4%.The result showed that this method could be used to replace the HPLC method for the determination of the content of oleuropein in the olive leaves or its products as the for mer was more simple,faster and lower cost than the latter.It can be looked as a reference methodfor the indirect determination of the active components in herbal materials or natural products.关键词：Olea europaea L.leaves;oleuropein;UV-Visible absorption spectrum;substraction
- 2028
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- 1197
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- 6
发布时间： - 摘要：An ultra performance liquid chromatography（UPLC）coupled with solid phase extraction（SPE） method was established for the determination of nine haloacetic acids（HAAs） in drinking water. The experimental conditions of UPLC and SPE were optimized. Three SPE cartridges with different sorbents were tested,and Lichrolut EN cartridges showed the best recoveries. A good baseline separation of target compounds were obtained in 6 minutes when using methanol and triethylamine phosphate buffer（pH 5.0） as mobile phase,triethylamine as ion pair reagent. The calibration curves of nine HAAs were linear in the certain concentration range with correlation coefficients of 0.995 7 -0.999 9. The limit of detection（LOD,S/N≥3） for monochloroacetic acid（MCAA） was 10.85 μg/L,and those for rest of target compounds were between 0.25 μg/L and 070 μg/L. Recoveries of HAAs at three spiked concentration levels ranged from 60% to 106% except for MCAA. The relative standard deviations（RSDs,n=5） of the method were between 2.0% and 5.7%. This method was applied in the determination of HAAs in tap water samples from a northern city in China,and five HAAs were detected.Therefore,the method was sensitive and convenient,and could be used in the trace determination of HAAs in drinking water.关键词：haloacetic acids;solid phase extraction;ion pair;ultra performance liquid chromatography;drinking water
- 2766
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- 3
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- 8
发布时间： - 摘要：Aqueous ZnS∶Mn quantum dots（ZnS∶Mn QDs） capped by thioglycolic acid and emitting fluorescence of 590 nm were obtained at room temperature.Based on the fluorescence quenching of ZnS∶Mn QDs caused by sulfadiazine sodium（SDS）,a simple,rapid and specific quantitative method was developed for the determination of SDS.Experimental conditions including temperature,reaction time and pH value of buffer affecting the detection for SDS were investigated.Under the optimal conditions,the calibration plot between the intensity ratio I0F/IF and the concentration of SDS was linear in the range of 625×10-6-375×10-4 mol?L-1 with a correlation coefficient of 0998.The limit of detection(LOD)（3σ/k） was 386×10-6 mol?L-1.The method was simple and rapid,and was applied in the determination of SDS in the injection sample with average recovery of 100%.In order to study the possible interaction mechanism,the influence of salt effect on the fluorescence intensity of QDs-SDS was discussed.The result indicated that SDS could bind to the ligand of ZnS∶Mn QDs surface through electrostatic force,which resulted in fluorescence quenching.关键词：ZnS∶Mn quantum dots;fluorescence detection;sulfadiazine sodium
- 2031
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- 1074
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- 2
发布时间： - 摘要：A confirmatory method using ultrahigh pressure liquid chromatography（UPLC） coupled with tunable ultraviolet detector（TUV） was developed for the determination of trace levels of tetracyclines,including chlortetracycline（CTC）,doxycycline（DC）,4 epitetracycline（ETC）,4 epichlortetracycline（ECTC）,4 epianhydrotetracycline（EATC）,oxytetracycline（OTC）,tetracycline（TC） and anhydrotetracycline（ATC）,in environmental water samples.The rare earth metal La ions were used as chelating agent to form a hydrophobic complex compound with TCs.Temperature induced ionic liquids dispersive liquid-liquid microextraction（DLLME）was used to concentrate the target compound.Effects of experimental conditions,including the kinds and amounts of ionic liquids,heating temperature,time of complexation and extraction,concentration of Triton X 114 and pH value，on extraction efficiencies were investigated.Under the optimum conditions,the calibration curves were linear in the range of 10-200 μg?L-1 for ETC,TC,DC and ATC,and 01-200 μg?L-1 for ECTC,CTC and EATC,and 10-200 μg?L-1 for OTC,respectively,with correlation coefficients（r2） more than 099.The limits of detection（LODs） ranged from 003 μg?L-1 to 579 μg?L-1,and the limits of quantitation（LOQs） were in the range of 009-191 μg?L-1.The spiked recoveries of eight target compounds in river water,fishpond water and leaching water of the pig farm soil were achieved in the range of 63%-96%,59%-94% and 55%-86%,respectively.The investigation results of environmental water samples in Beijing showed that 214 μg?L-1CTC and 009 μg?L-1 ECTC were detected in waste water from hoggery and no target compounds were found in the river water and fishpond water samples.As a result,this method could be applied in the rapid and convenient determination of eight tetracycline antibiotics in real environmental water samples.关键词：tetracycline antibiotics;ionic liquids;ultrahigh performance liquid chromatography;dispersive liquid-liquid microextraction（DLLME）
- 1997
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- 1215
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- 4
发布时间： - 摘要：A capillary zone electrophoresis（CZE） method was developed for the separation and quantitative analysis of water buffalo caseins.The effects of several parameters,including buffer system and concentration,pH value,urea concentration and injection time on the separation efficiency of water buffalo caseins were investigated on an uncoated fused silica capillary column（50.2 cm×75 μm id） using separation voltage of 25 kV and detection wavelength of 214 nm at 25 ℃.Under the optimal conditions,the calibration curves were linear in the range of 0.5-5.0 g/L for α CN,β CN and κ CN with correlation coefficients no less than 0.998 0.The spiked recoveries of three main caseins were in the range of 98%-106%.The relative standard deviations（RSDs） for migration time,peak area and peak height were no more than 067%，3.0% and 3.2%，respectively.This method was simple,rapid and accurate,and could be used for the quality control and quantitative analysis of water buffalo milk and dairy products.关键词：capillary zone electrophoresis;caseins;water buffalo milk;quantitative analysis
- 2749
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- 1013
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- 4
发布时间： - 摘要：A liquid chromatography-electrospray ionization tandem mass spectrometric (LC-ESI MS/MS) method was developed for the sensitive and selective determination of melamine migration in food contact materials,melamine tableware.The separation was performed on a strong cation exchange column using acetonotrile- 10 mmol/L NH4Ac/HAc (pH=4.0) (40∶60,by volume) as mobile phase at 35 ℃.The determination of melamine in melamine tableware sample was carried out by ESI MS/MS system under the muti reaction monitering mode(MRM).The result indicated that the calibration curves were linear over melamine concentration in the range of 3.00-130.00 μg/L for different simulant solutions with LODs（S/N=3） of 1.00-3.00 μg/L.The average recoveries at three spiked concentration levels of 10.00,50.00,80.00 μg/L were in the range of 98%-104% with relative standard deviations of 3.0%-3.6%.With the advantages of simple sample preparation,high sensitivity and strong anti interference capacity,the method could meet the requirements for determination of melamine migrantion from relevant products.关键词：melamine;LC-ESI MS/MS;melamine tableware;migration amount
- 2567
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- 936
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- 9
发布时间： - 摘要：A rapid and sensitive method was developed for the determination of the degree of esterification(DE) of Agave sisalana pectin(ASP) by diffuse reflectance Fourier transform infrared spectrotroscopy(DRIFTS).By processing the pectin spectrum obtained by DRIFTS with wavelet transform,the distortion of the original spectral signal caused by light scattering was effectively eliminated,for example,the signal to noise ratio(SNR) increased from 84 to 96,while the signal to baseline ratio (SBR) increased from 77 to 83.The precision(expressed as RMSE)of the wavelet transform for ten replicates of ASP h was 0011 62.The pectin spectra showed that the intensities of the absorption peak and peak area(KM) of the esterified group at 1 740 cm-1 and the carboxyl group at 1 630 cm-1 were closely related with the DE.A linear relationship existed between DE and KM1740/(KM1740+KM1630) with a correlation coefficient of 0988.For three pectin samples extracted from Agave sisalana with different technologies,the DE obtained for ASP w,ASP h and ASP u by DRIFTS were 7209%,6298% and 3531%,respectively.The results of Student t test indicated that no significant difference existed between the results obtained by acid base titration and DRIFTS methods.关键词：DRIFTS;Agave sisalana pectin;degree of esterification;wavelet transform
- 2366
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- 1797
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- 1
发布时间： - 摘要：Nano ZnO-MWCNTs was successfully synthesized by hydrothermal method with the assistance of polyethylene glycol（PEG）.A ZnO-MWCNTs composite modified glassy carbon electrode（ZnO-MWCNTs/GCE） was prepared by coating method.The electrochemical behavior of bisphenol A at the modified electrode was investigated by cyclic voltammetry（CV） in the presence of cetyltrimethylammonium bromide（CTAB）.The effects of buffer pH,CTAB concentration and accumulation time on the determination were investigated.The results indicated that bisphenol A showed a good electrochemical response at the modified electrode in pH 7.0 phosphate buffer in the presence of 80×10-5 mol/L CTAB.The oxidation peak current in CV curves at ZnO-MWCNTs/GCE was 7 times as high as that at the unmodified electrode.CV studies also indicated that the electrooxidation of bisphenol A at the modified electrode was adsorption controlled,and totally irreversible process involved in two electrons and two protons.Under the optimum conditions,the oxidation peak current of bisphenol A in DPV curves was proportional over the concentration range of 5.0×10-8-1.5×10-5 mol/L with a detection limit of 1.0×10-8 mol/L.The relative standard deviations（RSDs） of eight measurements were 4.6% for 1.0×10-5 mol/L bisphenol A.This method was applied in the determination of dissoluted bisphenol A in plastics with recoveries of 99%-107%.关键词：bisphenol A;CTAB;DPV;nano ZnO;CNT
- 2639
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- 958
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- 2
发布时间： - 摘要：A capillary column gas chromatographic method was developed for the separation and determination of thirteen plasticizers，including dimethyl phthalate acid ester（DMP），diethyl phthalate acid ester（DEP），dipropyl phthalate acid ester（DnPP），diisobutyl phthalate acid ester（DIBP），dibutyl phthalate acid ester（DBP），diamyl phthalate acid ester（DAP），bisphenol A（BPA），di n hexyl phthalate acid ester（DHP），butyl benzyl phthalate acid ester（BBP），di 2 ethylhexyl adipate（DEHA），di（2 ethylhexyl） phthalate acid ester（DEHP），dioctyl phthalate acid ester（DOP） and dinonyl phthalate acid ester（DNP） in plastic packaging materials for foodstuff. The analytes were extracted with hexane from samples by Soxhlet extraction technique，then purified by silica solid phase extraction. Three key factors such as rinse solvent，eluting solvent and eluting volume were optimized. Hexane and toluene（1∶1，by volume） were used as rinse solvents，2 mL ethyl acetate was used as eluting solvent. After filtration，the eluate was determined by gas chromatography with flame ionization detector（GC/FID）. The calibration curves of thirteen plasticizers were linear in the range of 01-1 000 mg/L with detection limits of 0005-0030 mg/L. The spiked recoveries ranged from 90% to 116% with relative standard deviations of 22%-49%. The method was successfully applied in the determination of plasticizers in plastic packaging materials for foodstuff.关键词：gas chromatography;plasticizer;Soxhlet extraction technique;solid phase extraction
- 1936
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- 1308
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- 12
发布时间： - 摘要：A GC/ECD method was developed for the determination of glucosides.The target compound（phenyl β D glucopyranoside） was derivatized with N methyl bis（trifluoroacetamide）（MBTFA）.The derivatization temperature and time were optimized.The result indicated that the best derivatization conditions were achieved at 60 ℃ for 50 min.Fluorine was introduced to the product molecule after derivatization to provide the fundamental element for the detection of GC/ECD.Linear study was conducted by using phenyl β D glucopyranoside as a typical compound,and a correlation coefficient（r2） of 0.999 6 was obtained in the range of 0.05-200 mg?L-1.Six glucosides could be accurately identified by GC/ECD after MBTFA derivatization.Repeatability experiment showed that this derivatization combined with GC/ECD determination had a good performance,the relative standard deviation for the corresponding peak area was lower than 3% in 72 h.This method was also compared with the GC-MS method,and the limit of detection of GC/ECD method was greatly lowered.The proposed method is applicable in the determination of trace amount of glucosides in real sample.关键词：glucoside;GC/ECD;N methyl bis（trifluoroacetamide）;derivatization;determination
- 2252
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- 947
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- 3
发布时间： - 摘要：A high performance liquid chromatographic（HPLC) method was established for the simultaneous determination of 3 drugs for diabetic mellitus （DM),including metformin hydrochloride,glipizide and telmisartan,in urine.The macromolecules in urine samples of DM patients were firstly removed by acetone precipitation method,and the supernatants were dried and redissolved in methanol.Then the extracts were analyzed by HPLC coupled with a diode array detector.The separation of analytes was performed on an Inertsil ODS column by gradient elution using acetonitrile-2.5 mmol/L SDS-20 mmol/L NaH2PO4 solution （pH=4.6) as mobile phase.The recoveries of 3 diabetic mellitus drugs were in the range of 82%-113% with relative standard deviations of 1.5%-3.1%.To obtain highest sensitivity,different wavelengths were chose for different drugs.The detection limits were 13.6 μg/L for metformin hydrochloride at 232 nm,31.5 μg/L for glipizide at 276 nm and 57.0 μg/L for telmisartan at 297 nm,respectively.The linear ranges of metformin hydrochloride,glipizide and telmisartan were in the range of 1.0-1000,1.0-1000,5.0-250.0 mg/L,respectively.The method was used to detect the contents of 3 drugs in real urine samples of DM patients.The result showed the method was applicable for the study of DM pharmaco metabonomics.关键词：diabetes mellitus;urine;high performance liquid chromatography;metformin hydrochloride;glipizide;telmisartan;simultaneous determination
- 1848
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- 986
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- 0
发布时间： - 摘要：A new cyclodextrin derivative heptakis(26 di O ethoxyethyl 3 O trifluoroacetyl) β cyclodextrin was synthesized by substituting the 26 OH groups of cyclodextrin derivative with ethoxyethyl groups and the 3 OH group with trifluoroacetyl group,and used to coat capillary column of gas chromatography by static method.The chromatographic properties and separation abilities of the capillary column were studied.The results showed that the stationary phase possessed good separation efficiencies to Grob test mixture,disubstituted benzene isomers(such as chlorotoluene,nitrotoluene and bromotoluene) and ten kinds of chiral compounds(such as α substituted propionate,1 (2′ nitrophenyl) ethanol,α methyl 4 chlorobenzyl cyanide,2 methyl 4 oxo 3 prop 2 ynyl cyclopent 2 enyl acetate).Among the test compounds,the separation ability of chiral stationary phase for 2 methylsulfonylpropionate was the best,the separation efficiency of methyl ester derivatives of chiral stationary phase for α substituted propionic was better than that of ethyl ester derivatives,and methyl ester and ethyl ester derivatives of α hydroxypropionic were better than that of α halogenpropionic.关键词：cyclodextrin derivatives;capillary gas chromatography;chiral stationary phase
- 1945
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- 870
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- 2
发布时间： - 摘要：A reverse phase high performance liquid chromatographic method was established for the determination of salicylic acid by using ionic liquids as mobile phase additives.The chromatographic separation of salicylic acid was performed on a ZORBAX ODS column（250 mm×4.6 mm id，5 μm）.The detection of salicylic acid was carried out by ultraviolet（UV） detection.The effects of detection wavelength，pH value，concentration and alkyl chain length of ionic liquids on the separation and determination of salicylic acid were investigated.The optimum chromatographic conditions were as follows:mobile phase:methanol-30 mmol?L-1 1 butyl 3 methylimidazolium tetrafluoroborate aqueous solution（pH 3.0,adjusted with acetic acid） （60∶40，by volume），UV detection wavelength:300 nm，flow rate:10 mL?min-1，column temperature:30 ℃.Under the optimal conditions，the retention time of salicylic acid was about 4.4 min.The calibration curve showed a good linearity over the range of 2-100 mg?L-1 for salicylic acid with a correlation coefficient of 0.999 9.The detection limit was 0.059 mg/L.The average spiked recovery was 100% with relative standard deviation of 0.11%.The method was successfully applied in the determination of the content of salicylic acid in the pharmaceutical of Zujunqing Tinctura.关键词：ionic liquid;high performance liquid chromatography;salicylic acid;ultraviolet detection;pharmaceutical
- 2394
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- 1145
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- 17
发布时间： - 摘要：A high performance liquid chromatography-tandem mass spectrometric（HPLC-MS/MS） method was developed for the determination of tulathromycin in pork tissues，such as liver,kidney,muscle,skin，fat and lung samples.The matrix effects of tulathromycin were also discussed in this paper.The samples were extracted with acetonitrile,and defatted with n hexane.The extract was cleaned up on a C18 solid phase extraction（SPE） cartridge.After washed with 4% amonium hydroxide in methanol and then condensed to nearly dryness at 40 ℃ water bath,the extract was redissolved with 50% acetonitrile.Tulathromycin was separated on a Penomenex Luna C18 column with a mobile phase of acetonitrile-2 mmol/L ammonium acetate（containing 1% fomic acid） at a flow rate of 0.25 mL/min.The column temperature was set at 35 ℃.The identification was carried out by MS/MS with electrospray ionization under positive scan and multiple reaction monitoring（MRM） mode.The quantitation was performed by the external standard method.The results showed that the calibration curves for all the tissues were linear（r﹥0.99） in the range of 10.0-500 μg/kg.The limits of detection（LODs） of tulathromycin in five tissues were in the range of 3-5 μg/kg and the limits of quantitation（LOQs） for all the tissues were 10 μg/kg.The spiked recoveries at three spiked concentration levels were in the range of 74%-96%.The RSDs of intra day and inter day were in the range of 4.0%-16% and 7.0%-15%,respectively.The method was proved to be simple and accurate,and could be applied in the determination of tulathromycin in real samples.关键词：high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS）;tulathromycin;pork tissue
- 2282
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- 1299
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- 1
发布时间： - 摘要：A liquid chromatography-tandem mass spectrometric（LC-MS/MS) method was established for the determination of tebufenozide,aldicarb,aldicarb sulfoxide and aldicarb sulfone in scallion.The samples were extracted with acetonitrile and ethyl acetate,respectively.It was found that the extraction efficiencies of 4 pesticides with acetonitrile were better than those with ethyl acetate.Co extractives were removed from the acetonitrile extracts using dispersive solid phase extraction（DSPE).The calibration curves were linear in the range of 10-120 μg/L with correlation coefficients（r2) more than 0.995.The limits of quantitation（LOQs)of 4 pesticides were all less than 10 μg?kg-1,and the average recoveries at the spiked level of 10 μg?kg-1 in scallion samples ranged from 60% to 110% with RSDs less than 5.0%.The results showed that this method was rapid,sensitive and specific,and was appropriate for the simultaneous identification and quantification of 4 pesticides in scallion.关键词：dispersive solid phase extraction（DSPE);liquid chromatography-tandem mass spectrometry（LC-MS/MS);multi reaction monitoring（MRM);pesticide residues;scallion
- 2726
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- 1020
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- 10
发布时间： - 摘要：A gas chromatography(GC）-negative chemical ionization-mass spectrometric(NCI/MS） method was established for the determination of 7 frequently used pyrethroid insecticides residues in beef.The sample was extracted with acetonitriles and cleaned up with neutral alumina chromatographic column,and then determined by GC-MS under the selected ion monitoring mode(SIM）.Good accuracy,precision and sensitivity were obtained.The calibration curves of 7 pyrethriods were linear between peak areas and concentrations in the range of 10-1 000 μg/L with correlation coefficients(r2） more than 0.997.The recoveries of 7 pyrethriods were in the range of 80%-108% at three spiked concentration levels of 10,20,50 μg/kg,with relative standard deviations(RSDs） less than 12.5%.The limits of detection(LOD） for all pyrethroid ranged from 0.10 μg/kg to 2.5 μg/kg and the limits of quantitation(LOQ） were in the range of 0.50-5.0 μg/kg.关键词：gas chromatography-negative chemical ionization mass spectrometry;column chromatography;selected ion monitoring;pyrethroid;beef
- 2379
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- 1108
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- 1
发布时间： - 摘要：A high performance liquid chromatography-electrospray ionization tandem mass spectrometric（HPLC-ESI MS/MS） method was developed for the determination of two plant growth regulators,eg.chlormequat and mepiquat,in rice,wheat flour,pear,tomato and ketchup samples.The samples were extracted with methanol-water（1∶1,by volume） and cleaned up on a Strata X C solid phase extraction column.The target compounds were separated on an Agilent ZORBAX RX SIL（1.8 μm,3.0 mm×100 mm） chromatographic column by equivalently elution using acetronitrilie-10 mmol/L ammonium acetate（containing 0.1% formic acid ） as mobile phase.The residues of chlormequat and mepiquat were determined under the electrospray positive ionization（ESI+） and multiple reaction monitoring（MRM） mode,and quantified by the matrix matched external standard method.The calibration curves for chlormequat and mepiquat showed good linearities in the range of 0.20-10 μg/L with correlation coefficients（r2） no less than 0.999 0.The limits of quantitation（S/N≥10） and limits of detection（S/N≥3） were in the range of 0.05-0.15 μg/kg and 0.02-0.05 μg/kg,respectively.The average recoveries of chlormequat and mepiquat from rice,wheat flour,pears,tomato and ketchup matries at three spiked levels of 0.20，5.0,10 μg/kg were in the range of 82%-102% and 80%-103%,respectively,with relative standard deviations of 3.8%-9.6% and 1.9%-10.0%,respectively.The method was sensitive and accurate,and could meet the requirements for the determination of chlormequat and mepiquat in foods.关键词：chlormequat;mepiquat;HPLC;tandem mass spectrometry;food
- 2133
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- 1013
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- 5
发布时间： - 摘要：A novel method of dispersive liquid-liquid microextraction（DLLME） and gas chromatography with flame photo detection（FPD） was developed for the determination of 23 organophosphorous pesticide residues（OPPs），including sulfotep,phorate,diazinon,disulfoton,chlropyrifos methyl,methyl parathion,runnel,fenitrothion,malathion,chlorpyrifos,fenthion,parathion,bromophos,pirimiphos ethyl,isofenphos methyl,phenthoate,methidathion,profenofos,ethion,triazophos,trithion,pyridaphethione and phosmet in water sample.The influence of extraction parameters including the types and volumes of extraction solvent and disperser solvent as well as extraction time were investigated. Under the optimum conditions,the calibration curves for 23 OPPs were linear in the range of 0.04-4.0 μg /L with correlation coefficients not less than 0.998. The limits of detection ranged from 0.002 μg/L to 0.016 μg/L. The recoveries of 23 OPPs at two spiked concentration levels of 0.08 μg/L and 2.0 μg/L were in the range of 75%-109% with relative standard deviations（RSDs） of 1.5%-13.3%.The DLLME technique showed the advantages of simplicity,rapidness,good recovery and high enrichment factor.关键词：dispersive liquid-liquid microextraction（DLLME）;gas chromatography（GC）;organophosphorus pesticides（OPPs）;water
- 2447
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- 1103
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- 17
发布时间： - 摘要：In this paper，two polypropylene（PP）/carbon black（CB） films containing 2.2% and 3.3% of carbon black（CB） contents were prepared by melt blending-masterbatch dilution method assisted with high efficiency dynamic mixer.Based on scanning electron microscopy（SEM） and optical microscopy（OM） images，the image analysis software，Image J，was firstly used to quantitatively characterize the dispersion and distribution of CB particles.The results of SEM analysis showed that the average area of CB particles was 0220 μm2 and the area distribution strictly conforms to exponent decay distribution.The results of OM analysis indicated that a small amount of CB agglomerates appeared when the CB content reached up to 3.3%.The dispersion index（D） of films with 2.2% and 3.3% of CB were 0.75 and 0.5，respectively，which indicated that high CB content was not conducive to CB dispersion.Furthermore，the average area of particles（0.209 μm2） in film with low CB content was less than that（0.220 μm2） in film with high CB content.However，their area distributions showed a great similarity and they both conformed to exponent decay distribution strictly.The results of OM were consistent with that of SEM.The image analysis software，Image J，can convert qualitative information into quantitative information and characterize comprehensively the dispersion of CB particles in polymeric matrix by combination with the dispersion indexes.关键词：polypropylene;carbon black;quantitative;SEM;OM;Image J;dispersion;distribution
- 2024
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- 993
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- 2
发布时间： - 摘要：An approach for genotyping of STR locus based on ultraviolet(UV) spectroscopy and support vector machine(SVM) was studied.Taking three different genotypes 10-10,11-13 and 13-13 of locus D5S818 as example,the conditions for PCR amplification and UV spectral detection on a DNA fragment containing the polymorphism sites were optimized.Under the optimal conditions,the ultraviolet spectra for the samples were obtained.Using these spectra as identifying variables,the SVM model of the three genotypes was established to overcome effectively the spectral colinearity,and a right prediction rate of 100% was obtained.The proposed method was simple,rapid and low cost,and could be indirectly used to determine the three genotypes of D5S818 locus based on PCR amplification and UV spectra of the samples without any pretreatment.关键词：short tandem repeat;ultraviolet spectroscopy;support vector machine;genotyping
- 1991
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- 814
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- 1
发布时间： - 摘要：Determination of trace dopamine has important significance on physiology，disease diagnosis and pharmaceuticals quality. In acid medium and surfactant，the fluorescence intensity of acridine orange could be quenched in the presence of graphene oxide.However,when dopamine was added into the system solution，the fluorescence intensity of the system was increased and the increasing fluorescence intensity was proportional to the amount of dopamine.Based on this,a novel method for the determination of dopamine was developed.The calibration curve was linear in the range of 0.05-12.0 μmol/L.The linear regression equation was ΔIF= 3.9+57.8c（μmol/L） （r=0.993 3） and the detection limit was 2.9 nmol/L. The method showed high sensitivity，and was successfully applied in the determination of dopamine in real samples with satisfactory results.关键词：acridine orange;graphene;dopamine;fluorescence quenching method
- 2390
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- 846
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发布时间： - 摘要：A microwave assisted extraction and gas chromatographic(MAE/GC）method was established for the simultaneous determination of 14 organochlorine pesticides,including the four isomers of DDT and BHC,pentachloronitrobenzene(PCNB）,tetrachloronitrobenzene,tetrachloroaniline,pentachloroaniline,procymidone and methyl 5 chlorophenyl sulfide(MPCPS）in starch.The samples were extracted with n hexane-dichloromethane mixed solvent(1∶2,by volume）.The extract was purified with a Florisil column using n hexane-dichloromethane(1∶5,by volume） as elution solvent.Experimental conditions were optimized,and three different extraction methods of ultrasonic extraction,microwave assisted extraction and soxhlet extraction were compared.Extraction conditions were studied by the orthogonal test.Under the optimal conditions,the calibration curves showed good linearities in the range of 20-200 μg/kg for 14 organochlorine pesticides.The recoveries of 14 organochlorine pesticides at spiked levels were in the range of 68%-108%.The detection limits ranged from 0.1 μg/kg to 0.3 μg/kg and the quantitation limits ranged from 0.5 μg/kg to 0.8 μg/kg.The method was easy to operate,rapid，accurate and sensitive,and was suitable for the determination of organochlorine pesticides residues in starch sample.关键词：microwave assisted extraction(MAE);GC;starch;organochlorine;pesticide
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