最新刊期
卷 30 ， 期 8 ， 2011
- 摘要：A n-octadecyl（C18）solid-microextraction fiber was prepared by sol-gel technology,and used in the extraction of organochlorine pesticides in water samples.The sol-gel solution was prepared by mixing appropriate amount of n-octadecyltriethoxysilan（C18-TEOS）,tetraethoxysilane（TEOS）,ethanol,hydrochloric acid and water.Then the n-octadecyl solid phase microextraction fiber was obtained from the polymerization of the sol-gel solution on the surface of the treated fused-silica fiber.Under the optimum conditions,the detection limits of organochlorine pesticides（OCPs）by gas chromatography with electron capture detector（GC/ECD） after extraction with the new C18 fiber were in the range of 0.01-0.24 μg/L,and the relative standard deviations（RSDs） varied from 3.0% to 13.3%.The method was applied in the detection of organochlorine pesticides in fishpond water,lake water and drinking water with satisfactory results.The extraction ability of the new fiber for OCPs was not changed significantly after it was dipped into four kinds of solutions（e.g.n-hexane,methanol,pH 2.0 and 9.0 water solutions） and repeatedly used for 50 times.The obtained fiber showed several advantages including porous structure,high stability and uniformly coating,and could be used as an alternative to the existing fibers for the extraction of OCPs.关键词：solid microextraction;octadecyl;sol-gel;organochlorine pesticide;gas chromatography
- 2496
- |
- 1109
- |
- 3
发布时间： - 摘要：The surface species on Mg3（VO4）2 catalyst prepared by citric acid complexation method,were investigated by X-ray photoelectron spectroscopy（XPS）techniques.In the oxidative dehydrogenation of cyclohexane to cyclohexene,the relationship between the catalytic performance over Mg3（VO4）2 catalyst and the surface species on the catalyst was studied.With the characterization of X ray diffraction（XRD）,scanning electron microscopy（SEM）,FT-IR spectroscopy（FT-IR） and H2-temperature programmed reduction（H2-TPR）techniques,the results indicated that well crystalline structures of Mg3（VO4）2 with a pure phase and a uniform granularity of particles of 110 nm mean size were obtained by the citric acid complexation. XPS spectra also indicated that the lattice oxygen was the main oxygen species among the three oxygen species（e.g.O-,O-2 and O2-） on the catalyst surface.Meanwhile,V4+ and V5+ species were coexisted on the catalyst surface.Although the molar amount of V5+ was a little more than that of V4+,the isolated VO4 species was the main vanadium species on the catalyst surface owing to the segregation of Mg.In the oxidative dehydrogenation of cyclohexane,gaseous oxygen participated in the reaction only after adsorption in other parts of the catalyst and then migrated through the lattice to the active sites by the reoxidation between V4+ and V5+.The characterization and the catalytic results also demonstrated that the catalytic performance was correlated to the lattice oxygen O2-and isolated VO4 species,which was beneficial to the improvement of the selectivity to cyclohexene.关键词：Mg3（VO4）2;X-ray photoelectron spectroscopy;cyclohexane;oxidative dehydrogenation
- 2690
- |
- 1133
- |
- 0
发布时间： - 摘要：A nanocomposite comprised of Fe3O4 magnetic nanoparticles（MNPs） and multi-walled carbon nanotubes（MWCNTs） was synthesized,and used as adsorbent in the determination of 16 PAEs in water samples by magnetic solid phase extraction（MSPE）and quantification by gas chromatography-mass spectrometry（GC-MS）.The synthesis nano material was characterized by Fourier transform infrared spectroscopy.The factors affecting the extraction efficiency,such as type and amount of elution solvent,desorption time,adsorption time and pH value of water sample,were investigated.The optimized conditions were as follows:elution solvent:1 mL toluene-acetone（1∶4）;desorption time:1 min;adsorption time:3 min;pH of water sample:5.0-7.0.The detection limits（S/N=3）for 16 PAEs were in the range of 0.035-0.255 μg/L and the quantitation limits（S/N=10） were 0.115-0.845 μg/L.The developed method was successfully applied in the analysis of 16 PAEs in tap water,lake water and river water.The recoveries at 3 spiked levels ranged from 87% to 112% with RSDs of 1.3%-11.9%.The results demonstrated that the MSPE method could be rapidly and effectively used in the monitoring of trace PAEs contaminants in water sample.关键词：magnetic multi-walled carbon nanotubes;magnetic solid phase extraction;phthalate acid esters(PAEs);gas chromatography-mass spectrometry;water sample
- 2457
- |
- 1277
- |
- 18
发布时间： - 摘要：A capillary electrophoresis coupled with electrochemiluminescence detection(CE-ECL)was successfully developed for the chiral separation and determination of a kind of antidepressants racemic drug(venlafaxine) enantiomers by employing sulfated β-cyclodextrin(S-β-CD)as the chiral selector.The determination conditions,including inlet and outlet buffers,injection time and voltage,separation voltage and detection potential were optimized.Unlike the traditional chiral separation method,the buffers used in the capillary inlet and outlet differed from each other.Under the optimum conditions,baseline enantioresolution and highly sensitive detection for the enantiomers of venlafaxine were achieved.The results showed that there was a linear relationship between Luminous intensity(I) and two venlafaxine enantiomers(S,R) concentrations(ρ) in the range of 0.1 μg/L to 1 000 μg/L.And the linear regression equations were IS=321.5ρ+30.1(r=0.999 6) and IR=319.3ρ +28.4(r=0.999 4),respectively.The detection limits(S/N=3) were obtained to be 0.01 μg/L and 0.05 μg/L，respectively,which were lower than the reported value about 3 orders of magnitude.The recoveries were in the range of 94%-100% with relative standard deviations no more than 3.2%.Therefore,the CE-ECL method has the application potential in chiral separation,and could be used to detect drug enantiomers in clinical pharmacology.关键词：venlafaxine;enantioseparation;capillary electrophoresis;electrochemiluminescence;S-β-CD
- 2077
- |
- 1025
- |
- 4
发布时间： - 摘要：One water-soluble fluorescent perylene diimide ［N,N′-bi（L-glutamic amine） perylene-3,4,9,10-tetracarboxylic diimide］(PTCDG)derived from the raw material 3,4,9,10-perylenetetracarboxy anhydride was synthesized and characterized by IR and 1H NMR spectra.A novel fluorescent switch was constructed based on PTCDG in presence of diamagnetic Fe2+or paramagnetic Fe3+.The switch turns off in presence of paramagnetic Fe3+owing to the PET quench,while it turns on in presence of diamagnetic Fe2+because of the absence of the PET quench.The magnetism reversability between Fe2+and Fe3+could be used to detect hydrogen peroxide and vitamin C.关键词：perylene derivative;fluorescent switch;synthesis;molecular recognition;hydrogen peroxide;vitamin C
- 2334
- |
- 942
- |
- 1
发布时间： - 摘要：An ultra performance liquid chromatography-tandem mass spectrometric method（UPLC-MS/MS） was established for the simultaneous determination of amoxicillin and polymyxin E residues in animal derived food.Mass spectrometric study on amoxicillin and polymyxin E was performed,and UPLC-MS/MS conditions were optimized.Samples were extracted with trichloroacetic acid solution.The protein was precipitated with lead acetate and the fat was removed with hexane.The other impurities were removed with HLB solid phase extraction cartridge.After concentration,the analytes were detected by UPLC-MS/MS and quantified with the matrix-matched standard.The limits of detection（LOD,S/N＞3）for amoxicillin and polymyxin E were 6 μg/kg and 15 μg/kg，and the limits of quantitation （LOQ,S/N＞10） were 20 μg/kg and 50 μg/kg,respectively.The average recoveries at three spiked concentrations in muscle,liver,kidney and fat were 76%-96% for amoxicillin and 74%-92% for polymyxin E with RSDs less than 10%.Furthermore,this method was applied in the determination of amoxicillin and polymyxin E residues in swine muscle,liver,kidney and fat for elimination study,and the withdraw times were caculated on the basis of the result.The result indicated that the method was simple,rebust and was suitable for the simultaneous quantitative detection of amoxicillin and polymyxin E residues in animal-derived food.关键词：amoxicillin;polymyxin E;residues;UPLC-MS/MS
- 2659
- |
- 1626
- |
- 2
发布时间： - 摘要：Bi2Mn0.1V0.9O5.35-δ（BIMNVOX-10） thin films were fabricated on LaNiO3（LNO）/Si（100） substrates by sol-gel process,using Bi（NO3）3·5H2O,NH4VO3 and Mn（CH3COO）2·4H2O as raw materials.The crystallite structure and morphology of BIMNVOX.10 films were investigated by X-ray diffraction（XRD）,scanning electron microscope（SEM） and atomic force microscope（AFM）.The results indicated that the films assumed preferred（001）orientation and the film thickness was about 300 nm with a uniform grain distribution.The electrical properties and ferromagnetism were measured by impedance analyzer and physical property measurement system.At a lower electric field,the I-V curves of BIMNVOX-10 films obeyed a Poole-Frenkel emission mechanism,suggesting that the conduction mechanism of leakage current may be attributed to the ohmic conduction.While at a higher electric field above 1.7 V,the current resulted from the combination of Schottky and space charge limited conduction emission mechanism.A low frequency dielectric dispersion was observed in the BIMNVOX.10 thin films.This behavior may be originated from the short distant diffusion of oxygen vacancies.The ac conductivity spectra obeyed Jonscher’s form.It revealed that the existence of low frequency independent region（dc conductivity） arised from the intra well hopping domination.Plateau at higher frequencies was referred to the bulk effect associated with ac conductivity（inter-well hopping domination）.The conductive property mainly contributes to the grain resistivity and the impedance spectra for the films differ from the idea Debye model.A weak room temperature ferromagnetism（FM） was observed in the BIMNVOX.10 thin films with remnant magnetization of 8.14×10-7 A/m（1.05×10-4 emu/g） at a magnetic field of 5.57×105 A/m（7 kOe）,in which the oxygen vacancy defects may play a critical role for the FM.关键词：Bi2Mn0.1V0.9O5.35-δ（BIMNVOX.10）;electrical conductivity;ferromagnetism;oxygen vacancies
- 2121
- |
- 1013
- |
- 0
发布时间： - 摘要：An electrochemical DNA biosensor based on hexaammineruthenium（Ⅲ） chloride （［Ru（NH3）6］3+） as a hybrid indicator was fabricated for the detection of PML/RARα fusion gene in acute promyelocytic leukemia（APL） by chronocoulometry（CC）.The DNA probes were immobilized onto the surface of electrode via Au-S covalent bond，followed by the hybridization with target DNA complementary sequences.CC method was employed to monitor the hybridization events and contrast the charge variations before and after hybridization to quantitate the target DNA complementary sequences.Owing to the different amounts of ［Ru（NH3）6］3+ caused by electrostatic combination with DNA sequences before and after hybridization，the charge difference was formed.The increase of the different charge of ［Ru（NH3）6］3+ was observed upon the hybridization of the probe with target DNA，and the charge difference of ［Ru（NH3）6］3+ was enhanced with the increase of target DNA sequence concentration.Under the optimal conditions，experimental results indicated that the biosensor showed a good specificity to distinguish the complementary sequence from different mismatch sequences and could be used to detect PML/RARα fusion gene quantitatively.The relationship between the charge difference and logarithmic （lgc） of target sequence concentrations was linear in the concentration range of 1.0×10-12-1.0×10-8 mol·L-1，and the detection limit was 4.0×10-13 mol·L-1.Therefore，as an electrochemical DNA indicator of the DNA sensor，the［Ru（NH3）6］3+can be used to detect the complementary sequence of PML/ RARα fusion gene qualitatively and quantitatively.关键词：DNA electrochemical hybridization biosensor;chronocoulometry;［Ru（NH3）6］3+;PML/RARα fusion gene
- 2784
- |
- 1306
- |
- 3
发布时间： - 摘要：A simple and rapid method was developed for the simultaneous determination of 22 food additives in carbonated beverages by ultra high performance liquid chromatography（UPLC）.The sample was degassed by ultrasonic and added 10% ethanol.The pH was regulated to 8.0 using 25% ammonira-water （1∶1）.The separation was achieved on a BEH C18 column（1.7 μm，2.1 mm×50 mm） in 15 min by using 0.01 mol/L NH4Ac（pH 5.8-6.0） and acetonitrile as mobile phase with a flow rate of 0.2 mL/min at 35 ℃. A diode array detector was used to detect at 217,232 and 257 nm.The quantification was performed by the external standard method.The method showed good linearities for 22 food additives with correlation coefficients（r） more than 0.995.The detection limits ranged from 0.02 mg/L to 0.50 mg/L.The average recoveries for 22 food additives from spiked carbonated beverage samples were in the range of 81%-107% with relative standard deviations（RSDs）of 1.0%-12.9%.With the advantages of simplicity,sensitivity and repeatability,the method could meet the requirements for determination of food additives in carbonated beverages at home.关键词：ultra performance liquid chromatography（UPLC）;carbonated beverage;food additive;determination
- 2479
- |
- 1192
- |
- 10
发布时间： - 摘要：The morphologies，chemical composition and crystal structure of the nanorod arrays on the sulfurated hydrorefining catalyst surface were studied by scanning electron microscopy(SEM),high resolution transmission electron microscopy(HRTEM),selected area electron diffraction(SAED)and X-ray energy disperse spectroscopy(EDS).The nanorod arrays were observed by SEM,which widely distributed on the catalyst surface.The nanorod arrays grew outward from the surface and assumed their regular shapes with lengths of 500-1 500 nm and diameter of 200-500 nm.According to the result of HRTEM,the nanorod arrays consisted of nanorods possessing single crystal structure with diameters of 40-100 nm.The image of crystal lattice fringe was also observed by HRTEM.The results of TEM-EDS showed that the nanorod arrays were composed of Ca,S and O.By means of the double tilt method,SAED patterns with different orientations were obtained.According to the chemical composition of the nanorod arrays shown by EDS and the crystallology information from the diffraction patterns of SAED patterns,the nanorods were confirmed to be of hexagonal calcium sulphate.The formation of calcium sulphate resulted from Ca originated from quartz sands which were mixed with catalysts in the fixed bed.Therefore,in order to prevent the generation of calcium sulphate,the quartz sands should be properly pretreated by calcining at high tempreture,acid cleaning and alkali cleaning,to eliminate the influence of calcium sulphate on catalytic activity in hydro-refining process.关键词：hydrorefining catalyst;nanorod arrays;calcium sulphate;SEM;HRTEM
- 2420
- |
- 1105
- |
- 0
发布时间： - 摘要：A method was developed for the simultaneous determination of fat-soluble vitamin A,E and K3 in dried okra by reversed phase high performance liquid chromatography coupled with diode array detection.The sample was first extracted with ethanol and followed by saponification with 50% KOH solution,then extracted with petroleum ether.The extract was separated on an Agilent Eclipse XDB C18 column（150 mm× 4.6 mm,5 μm i.d.） at 30 ℃,using methanol as mobile phase at a flow rate of 1.0 mL/min.The target compounds were simultaneously detected at 325,290,244 nm,respectively,and quantified by the external standard method.The results showed that the linear ranges for fat-soluble vitamins A,E,K3 were in the range of 0.1-20.0 mg/L with correlation coefficients more than 0.99.The spiked recoveries of three fat-soluble vitamins from dry okra sample were in the range of 88%-95% with RSDs of 0.8%-3.9%.The limits of detection（LODs,S/N=3）of VA,VE and VK3 were 0.3,0.6,0.1 mg/kg,respectively,and the limits of quantitation（LOQs,S/N=10） were 1.0，2.0,0.3 mg/kg,respectively.The developed method was simple and accurate,and could meet the demands for actual detection.关键词：high performance liquid chromatography（HPLC）;fat-soluble vitamins;vitamins A,E,K3;okra
- 2825
- |
- 1039
- |
- 9
发布时间： - 摘要：Different pretreatment methods（e.g.acetonitrile extraction，acetonitrile extraction-solid phase extraction（SPE），matrix solid phase dispersion（MSPD） extraction and MSPD-SPE） for the simultaneous analysis of penicillin,ampicillin and amoxicillin in chicken tissues were compared with HPCE.The results indicated that,among these methods,the MSPD method was of high precision,high recovery,easy operation and good practicability.Under the optimal chromatographic conditions,the calibration curves were linear in the range of 100-1 000 μg／L for penicillin and ampicillin,and 50-1 000 μg/L for amoxicillin.At the spiked concentrations of 50,500,1 000 μg／kg，the recoveries of these three drugs in chicken tissues ranged from 73％ to 96％ with relative standard deviations（RSDs） of 2.9％-9.8％.The intra-RSDs and inter-RSDs ranged from 4.0％ to 12.0％.The detection limits of penicillin,ampicillin and amoxicillin were 20,30,10 μg／kg,respectively,and their quantitation limits were 50,50,40 μg／kg,respectively.The method could meet the requirements for the residue analysis in accuracy and precision.关键词：matrix solid phase dispersion extraction;high performance capillary electrophoresis（HPCE）;sample pretreatment;penicillins;residues;chicken tissues
- 2293
- |
- 1112
- |
- 2
发布时间： - 摘要：The electrocatalytic oxidation behaviors and electrochemical determination of glutathione（GSH） were investigated at nano-TiO2-caffeic acid modified carbon paste electrode（nano-TiO2-CFA/CPE）.The experimental results indicated that GSH showed a very poor electrochemical response at CPE and nano-TiO2/CPE,but GSH at nano-TiO2-CFA/CPE exhibited a better electrocatalytic activity than that at CFA/CPE.The kinetic properties of GSH were discussed at nano-TiO2-CFA/CPE by cyclic voltammetr（CV）and chronoamperometry（CA）.The catalytic oxidation peak current of GSH versus its concentration had a good linear relationship in the concentration range of 9.0×10-6 -1.0×10-3 mol·L-1 with a correlation coefficient of 0.997 5,and a detection limit of 8.85×10-7 mol·L-1 by linear sweep voltammetry（LSV）.The method was applied in the determination of GSH contents in real samples with satisfactory results.关键词：glutathione;nano-TiO2;caffeic acid;modified carbon paste electrode;electrocatalytic oxidation;electrochemical determination
- 2445
- |
- 1068
- |
- 3
发布时间： - 摘要：A high performance capillary electrophoresis（HPCE） method was established for the separation and quatitative determination of saikosaponin a and saikosaponin d in Bupleuri Radix by using sulfobutyl ether-β-cyclodextrin（SBE-β-CD）and β-cyclodextrin（β-CD） as dual cyclodextrin（CD） system.Experimental conditions,such as the concentration of running buffer,the types and concentration of CDs,separation voltage and sample medium,were investigated.The results indicated that saikosaponin a and saikosaponin d could be baseline separated on an uncoated fused sillica capillary column（60 cm×50 μm i.d.,effective length:53 cm） using 20 mmol/L tris（hydroxymethyl）aminomethane-20 mmol/L SBE-β-CD-25 mmol/Lβ-CD（pH 9.9） as running buffer.The separation voltage was set at 15 kV and the detection wavelength was 210 nm.Samples were injected into capillary by gravity for 10 s and p-nitrobenzoic acid was used as the internal standard.Under the optimal conditions,the calibration curves of saikosaponin a and saikosaponin d were linear in the concentration ranges of 60-300 mg/L（r=0.999 7） and 20-100 mg/L （r=0.999 5）,respectively.The average recoveries of saikosaponin a and saikosaponin d were 102% and 100%,respectively,with RSD of 1.2% and 2.3%.The HPCE method was convenient,rapid and well repeatable,and was suitable for the quantitative analysis of saikosaponin a and saikosaponin d in Bupleuri Radix.关键词：high performance capillary electrophoresis（HPCE）;Bupleuri Radix;saikosaponin a;saikosaponin d
- 3101
- |
- 1166
- |
- 2
发布时间： - 摘要：An Ultrasound-assisted extraction and hydrolyzation plus high performance liquid chromatographic（HPLC） method was developed for the determination of chloramine T in cosmetics.A liquid chromatography-tandem mass spectrometric（LC-MS/MS） method was also established for the verification of the results.Different cosmetic products,e.g.cream,lotion,powder,shampoo and toothpaste, were extracted ultrasonically and hydrolyzed with hydrochloric acid solution.The hydrolyzate was isolated by liquid-liquid extraction with ethyl ether.The determination of chloramine T was performed by HPLC on an Agilent Extend C18 column（4.6 mm×250 mm,5μm） using acetonitrile-water as mobile phase at a detection wavelength of 224 nm, and quantified by the external standard method.The verification analysis was achieved by LC-MS/MS method on an Agilent Poroshell C18 column（4.6 mm×100 mm,2.7 μm）,under positive electrospray ionization and multiple reactions monitoring（MRM） mode.For p toluenesulfonamide,the MS/MS detection transitions were m/z 172.04>91.10 and m/z 172.04>155.02,in which m/z 172.04>91.10 was used as the quantitative transition.Under the optimal conditions,the calibration curve was linear in the range of 1.0-500.0 mg/L,with correlation coefficient of 0.999 9.The limit of quantification（LOQ） was 16.5 mg/kg.The mean recoveries at three spiked levels were in the range of 81%-103%with RSDs of 1.0%-7.4%.The method was simple,rapid,accurate and sensitive,and was suitable for the determination of chloramine T in cosmetic samples.关键词：liquid chromatography;liquid chromatography-tandem mass spectrometry;ultrasound-assisted extraction and hydrolyzation;chloramine T;p toluenesulfonamide;cosmetics
- 2328
- |
- 1195
- |
- 1
发布时间： - 摘要：An ultrasound/microwave assisted extraction and gas chromatography with electron capture detector（GC/ECD） was developed for the simultaneous determination of seven polybrominated diphenyl ethers（PBDEs）in soil.The influences of several parameters,such as the type and dosage of solvent,microwave power and time of extraction,on the extraction efficiencies were investigated.The optimal operation conditions were as follows：extraction solvent：50 mL n-hexane-acetone（1∶1）,microwave power：90 W,and extraction time：10 min.Under the optimal extraction conditions,good linear relationships were obtained in the concentrations of 10-400 μg·L-1 for all the analytes with correlation coefficients(r2) of 0.999 1-0999 7.The limits of detection were between 0.21 ng·g-1 and 0.63 ng·g-1.The spiked recoveries of PBDEs in soil were between 75％ and 121％ with relative standard deviations （RSDs） of 5.2％-7.8％. The proposed method was applied in the determination of PBDEs in wetland soil samples collected from Chongming Island of Shanghai,in which two PBDEs （e.g.BDE-28 and BDE-47） were found.The results were in agreement with those obtained by the Soxhlet-GC method.With the advantages of simple procedures,good sensitivity and high accuracy,this method could be used for the monitoring of PBDEs in soils.关键词：ultrasound/microwave assisted extraction;gas chromatography;soil;polybrominated diphenyl ethers(PBDEs)
- 2751
- |
- 1044
- |
- 6
发布时间： - 摘要：An effective method was established for the simultaneous determination of six kinds of banned organophosphorous flame retardants，including tris（1-aziridinyl） phosphine oxide（TEPA）,tris（2-chloroethyl）phosphate（TCEP）,tris（2,3-dichloropropyl）phosphate（TDCP）,bis（2,3-dibromopropyl） phosphate（DDBPP）,tri-o-tolyl phosphate（TOCP） and tris（2,3-dibromopropyl）phosphate（TRIS）,in textiles by gas chromatography tandem mass spectrometry（GC-MS/MS） combined with ultrasonic extraction.The organophosphorous flame retardants in textiles were first ultrasonically extracted with acetone,and then analyzed by GC-MS/MS under multiple reaction monitoring （MRM） mode.The linear ranges of TEPA,TCEP,TDCP,DDBPP,TOCP and TRIS were 9.17-366.80，0.95-75.98，1.04-83.20，41.60-832.00，3.80-75.90，40.48-809.60 μg/L,respectively,and their quantitation limits（S/N=10）were 3.0，0.2，0.3，25.0，2.5，29.0 μg/kg,respectively.The spiked recoveries varied from 83％ to 96％ with RSDs of 3.7％-9.8％.The developed method was simple,rapid,sensitive and accurate,and could satisfy completely the demand of the analysis of banned organophosphorous flame retardants in textiles.关键词：ultrasonic extraction;gas chromatography tandem mass spectrometry（GC-MS/MS）;textiles;organophosphorous flame retardant
- 3794
- |
- 1433
- |
- 19
发布时间： - 摘要：A method was developed for the overcoming matrix effects in gas chromatography analysis of organophosphorus pesticide residues in vegetable by using L-gulonic acidγ-lactone as a masking reagent.Effects of overcoming matrix effects while using L-gulonic acidγ-lactone were investigated.The result indicated that the addition of 1.0 g/L L-gulonic acidγ-lactone could significantly improve the chromatographic behaviors of susceptible pesticides，such as methamidophos，acephate，omethoate，moncrotophos，on gas chromatography，the peak intensities of four pesticides were 2.8,9.1,10.4 and 4.8 times higher than those in acetonitrile，respectively.There were no negative effects on the chromatographic behavior of unsusceptible pesticides（e.g.chlorpyrifos and parathion）.Five 0.25 mg/L standard solutions with the addition of masking reagent were injected at the beginning and every 25 samples in the sequence（100 GC injections）.The RSDs for peak heights and peak areas of five injections were 2.4％-11.8％ and 4.3％-7.5％，respectively.The average recoveries of the selected pesticides were between 80％ and 120％ with RSDs of 1.6％-13.5％.The method was simple and effective，and could be used to overcome matrix effects in GC analysis of organophosphorus pesticide residues in vegetables.关键词：L-gulonic acid γ-lactone;organophosphorus pesticide;matrix effects;overcome
- 2221
- |
- 910
- |
- 3
发布时间： - 摘要：According to the demand of home-made spectrometer,a radio frequency（RF） signal amplifier was developed.This RF signal amplifier,composed of amplifier circuit module and coupling coil,could combine with RF signal generator to drive the radio frequency quadrupole（RFQ）.The amplifier can carry out 30 times magnification,and provide resonance frequency of 1.4 MHz,peak to peak voltage Vp-p of 0-600 V RF signals for self-made RFQ.The developed RFQ was used to transmit the ions generated in atmospheric pressure ion source to a home-made desktop orthogonal-in-jection time-of-flight mass analyzer.With the radio frequency signal amplifier described in this paper,the ions with m/z equal to 30-600 amu can be transmitted efficiently.关键词：radio frequency quadrupole（RFQ）;RF signal;magnifier;time-of-flight mass spectrometer（TOF MS）
- 2365
- |
- 923
- |
- 6
发布时间： - 摘要：The voltammetric behaviours of ascorbic acid（AA）,uric acid（UA） and dopamine（DA） were studied at glass carbon electrode.Well-defined volammetric oxidation peaks for the three compounds were obtained by differential pulse voltammetry（DPV） in pH 5.7 Britton-Robinson buffer.However,serious overlappings of individual voltammetric peaks were observed for the mixtures of these compounds,which were difficult to determine by normal methods.To facilitate the resolution of these complex voltammograms,different calibration models were investigated based on the different chemometrics methods,including principal component regression（PCR）,partial least squares（PLS），radial basis function-artificial neural networks（RBF-ANN） and principal component analysis-radial basis function-artificial neural networks（PCA-RBF-ANN）.The results indicated that the lowest relative prediction error（RPE） was obtained with the PCA-RBF-ANN method.The method was successfully applied in the analysis of synthetic mixtures and urine sample without separation and purification.The developed method was then applied in the analysis of the compounds with satisfactory results.关键词：dopamine（DA）;uric acid（UA）;ascorbic acid（AA）;differential pulse voltammetry;chemometrics
- 2236
- |
- 992
- |
- 3
发布时间： - 摘要：Chemical fingerprints of Radix Paeoniae Rubra（RPR)from different places of origin were studied by chemical oscillation system of H2SO4-CH2（COOH)2-Ce2（SO4)3-KBrO3.Effects of various variables on the chemical oscillation system were studied.The optimal conditions were as follows:12 mL 3.0 mol/L sulfuric acid,6 mL 0.4 mol/L malonate,3 mL 0.005 mol/L cerium ammonium sulfate,3 mL 0.2 mol/L sodium bromate and 0.4 g RPR powder at 35 ℃.The results indicated that,under the optimal conditions,the chemical fingerprints of RPR from different places of origin（Bozhou,Heze,Chifeng and Hailaer)showed significantly different characteristics,such as the maximum potential,induction time and oscillation lifetime,etc.The results also indicated that the RPR from Bozhou had the shortest induction time（133.76 s),but the longest oscillation lifetime（554.89 s).The RPR from Hailaer had the longest induction time（214.17 s),but the shortest oscillation lifetime（only 237.11 s).The chemical fingerprints could be used to identify the origins of RPR.The method is simple,rapid and sensitive,and without need sample preparation.关键词：chemical fingerprint;chemical oscillation system;Radix Paeoniae Rubra;identify
- 2388
- |
- 971
- |
- 3
发布时间： - 摘要：The antibiotic experiment of extractive from Allium fistulosum and Allium tuberosum root with petroleumether and ethylacetate against Fusarium oxysporum f.sp.cubense was investigated.The results showed that the most conspicuous inhibitory effect on the germ was from the extract with petroleumether from Allium fistulosum stem.Compositions of the extract were analyzed by GC-MS，in which two main compounds,disulfide（42.07%） and thioxane（16.29%） were obtained.The extracts with petroleumether from all the parts of Allium fistulosum and Allium tuberosum root，as well as the secretions in water of Allium fistulosum and root of Allium tuberosum dissolved with ethylacetate were further detected by GC-MS.The secretions detected from petroleumether were 24，9，11，27，and those from the ethylacetate were 19 and 7.The petroleumether extracts contained many sulfocompounds，which were mainly the disulfide，occupying 31.09% in Allium fistulosum root，42.07% in stem and 26.20% in leaf，but little in Allium tuberosum root.Compounds containing carbazole were detected from secretions in water of Allium fistulosum root，up to 28.03%，and phenethylamine，benzeneacetic acid，cyclohexene-1-one semicarbazone，indole etc.were detected from secretions in water of Allium tuberosum root.关键词：Allium fistulosum;Allium Tuberosum;Fusarium oxysporum f.sp.cubense;antibiotic composition;GC-MS
- 2225
- |
- 1016
- |
- 3
发布时间： - 摘要：In recent years，accompanied by the extraordinarily rapid developments in the capillary electrophoresis（CE） online coupling techniques with mass spectrometry（MS） and laser induced fluorescence（LIF） spectrometry，CE has been widely used in the areas of life science，environmental protection and food detection.In order to suppress the adsorption of analytes onto the capillary surface and enhance the separation performance and repeatability，coating the capillary column with functional materials becomes the most efficient and commonly used approach.In this paper，the latest progress about covalent and non covalent bonded capillary coatings is reviewed based on the different materials and preparation mechanisms of the capillary coatings.The difference of coatings are compared，and the future direction of coating development is discussed.关键词：capillary electrophoresis;coated capillary column;non covalent bonded coating;covalent bonded coating
- 2340
- |
- 1062
- |
- 2
发布时间：
- Address：100 Xianlie Middle Road, Guangzhou Postal code：510070
- Tel：020-87684776,37656606 Fax：020-87684776 Email：fxcsxb@china.com
- Technical support is provided by Beijing Founder electronics co., LTD 粤ICP备12017312号-3
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0