最新刊期
卷 32 ， 期 7 ， 2013
- 摘要：A combined method for monitoring peptide coupling carrier protein prepared immunogen was established to get a carbodiimide coupling method which has the advantages of simple operation，high success rate and wide range of application. The optimized coupling method was applied in the preparation of immunogens for a variety of tumor-associated peptide biomarkers.Using synthesized SP0104 as the peptide，BSA （bovine serum albumin） as the carrier protein and EDC（carbodiimide） as the coupling reagent，the key conditions such as the activation method of reactants，the coupling time and the ratio of three reactants were investigated.The coupling ratio of UV and coupling rate of SDS-PAGE were used to monitor the compounds derived from the coupling reaction.The addition sequence of reagents was optimized as follows∶The peptide was mixed with BSA firstly，and then added into carbodiimide solution.The mass ratio of SP0104∶BSA∶EDC was 1∶1∶1, and coupling time was 12 h.The coupling ratio was between 4∶1 and 12∶1 and the coupling rate was between 9% and 20%.The antibody titer of purified SP0104 was 1∶80 000, and the polyclonal antibody successfully captured the peptide antigen SP0104 by the analysis of MALDI-TOF mass spectrometry.The optimized coupling method was applied in the peptide immunogen preparation of SPC09，SPC15，SPG01，SPG03 and SPG04.All the antibody titers of five immune-serum were over 1∶10 000，and the maximum reached up to 1∶512 000.The established combined monitoring method for carbodiimide coupling peptide and carrier protein was simple and effective，and could improve the success rate of peptide antibody preparation.关键词：peptide coupling;carbodiimide coupling;monitoring;antibody
- 2103
- |
- 3
- |
- 1
发布时间： - 摘要：A liquid chromatography-tandem mass spectrometric（LC-MS/MS） method with subcritical water extraction was developed for the determination of β-agonists and chloramphenicol in pork.Enzymatic hydrolysis was firstly used during the preparation of pork，then the target compounds were extracted with subcritical water and cleaned up by C18.The LC separation was performed on an Agilent XDB-C18 column（4.6 mm×50 mm，1.8 μm）.The veterinary drugs were determined by MS/MS in MRM mode and quantified by the matrix matched internal standard method.The calibration curves showed good linearities in the ranges of 1.0-32.0 μg/L for salbutamol and ractopamine with quantitation limits（S/N>10） of 0.5 ng/g and detection limits（S/N>3）of 0.25 ng/g，and 0.2-6.4 μg/L for clenbuterol and chloramphenicol with quantitation limits（S/N>10） of 0.1 ng/g and detection limits（S/N>3）of 0.05 ng/g.The correlation coefficients were all larger than 0.99.The recoveries of veterinaries in pork at three spiked levels-ranged from 79.2% to 113.6% with relative standard deviations（RSDs）of 3.2%-12.0%.The sensitivity，accuracy and precision of the method could meet the technical standard for veterinary drugs determination，and the method was suitable for the determination of β-agonists and chloramphenicol in pork.关键词：subcritical water;liquid chromatography-tandem mass spectrometry（LC-MS/MS）;pork;chloramphenicol;β-agonists
- 2172
- |
- 1226
- |
- 2
发布时间： - 摘要：Simultaneous separation and purification of saturated and aromatic hydrocarbons in crude oil by using solid-phase extraction（ SPE ） cartridges of silica-cyanopropyl（ SiO2/C3-CN） is presented in this paper.The results indicate that，compared with the separation effect of silica cartridges，the silica-cyanopropyl catridge’s effect is better，and saturated and aromatics hydrocarbons could be separated completely with 4.5 mL C6H14 and CH2Cl2/C6H14（1∶1） as elution.The recoveries of saturated and aromatics hydrocarbons are 98% and 99%，respectively.However, the co-eluting phenomenon exists between aromatic（such as naphthalene and its methyl homologues，acenaphthylene，etc.） and saturated hydrocarbons through the silica cartridges.The determination results of crude oil sample indicate that the elution behaviors of the saturated and aromatic hydrocarbon fractions with C6H14，CH2Cl2-C6H14（1∶1） are completely consisitent with the standard mixtures through the silica cyanopropyl cartridges.With the advantages of practicality，reliablity，easy to operate，low reagent consumption and good precision（ with RSDs of 4.2%-8.5% ），the method is suitable for the quantification of crude oil samples with complicated matrices.关键词：solid phase extraction（SPE）;silica-cyanoproply combined cartridges;saturated hydrocarbons;aromatic hydrocarbons
- 2169
- |
- 1343
- |
- 4
发布时间： - 摘要：The variation of water cluster structure of Zn（NO3）2 dilute aqueous solution before/after frozen/thawed disposition and its effect on the conformation of bovine serum albumin（BSA） were studied in this paper.The conductivity，density and viscosity of Zn（NO3）2 dilute aqueous solution before/after frozen/thawed disposition were determined to show the variation of water cluster structure of Zn（NO3）2 dilute aqueous solution，which indicated that the freezing/thawing disposition on Zn（NO3）2 dilute aqueous solution resulted in the obvious increase of conductivity and viscosity，and decrease of density，because of the forming of smaller water cluster structure binded by hydrogen bond in Zn（NO3）2 dilute aqueous solution after frozen/thawed disposition.The conformation of BSA interacted with Zn（NO3）2 dilute aqueous solution before/after frozen/thawed disposition was studied by laser confocal Raman microspectroscopy，Fourier transform infrared（FTIR） spectroscopy and circular dichroism（CD） spectrum.The result indicated that Zn2+ ions affect the amideⅠbands of BSA，causing the decrease of the α-helices in BSA.The configuration of disulfide bonds and the microenvironment of tyrosine and tryptophan changed owing to the effect of Zn2+ ions on BSA.The freezing/thawing disposition on Zn（NO3）2 dilute queous solution decreased the effect on the conformation of BSA，which caused less decrease of α-helices in BSA amideⅠbands，and weakened the effect on the microenvironment of tyrosine.It can be concluded that the freezeing/thawing disposition on Zn（NO3）2 dilute aqueous solution can change the water cluster structure of the dilute aqueous solution，resulting in the change of the physicochemical property of Zn（NO3）2 dilute aqueous solution，and then weakened its effect on the conformation of BSA.关键词：water cluster structure;Zn（NO3）2;bovine serum albumin（BSA）;conformation;spectrometry
- 2083
- |
- 1048
- |
- 0
发布时间： - 摘要：A hybrid high performance liquid chromatographic method was developed for the determination of alkyphenol ethoxylates（NPnEO and OPnEO，n=0-30）in detergent products and cosmetics.Different types of samples were extracted by ultrasonic assisted extraction using a mixture of acetonitrile-water（8∶2）.The chromatographic separation was conducted with a reverse phase column of C18（Poroshell 120 EC-C18,75 mm×4.6 mm,2.7 μm）coupled with a HILIC-Silia column（Atlantis HILIC Slica,250 mm×4.6 mm,5 μm）by gradient elution using acetonitrile-10 mmol/L ammonium acetate as mobile phase.The detection was performed with a fluorescence detector（FLD）.A quantitative model was established based on fluorescence molar absorption coefficients of NPnEO and OPnEO.With the quantification of the hybrid standard solution of NPnEO and OPnEO,the fluorescence molar absorption coefficients of NPnEO and OPnEO were determined.The average molecular weight of NPnEO and OPnEO in real samples were measured,and the concentrations of the analytes were calculated with the fluorescence molar absorption coefficients.With this method,the average recoveries for APEOS ranged from 99.0% to 105.7% with relative standard deviations no more than 12.5%,and the limit of quantitation were both 40.0 mg/kg.关键词：detergent products;cosmetics;alkyphenol ethoxylates（APEOS）;fluorescence molar absorption coefficient;high performance liquid chromatography
- 2204
- |
- 1197
- |
- 0
发布时间： - 摘要：An ionic liquid/Silica sol/Nafion-Ru（bpy）2+3 modified gold electrode was prepared.The electrochemical and ECL characteristies of Ru（bpy）2+3 and levofloxacin at the modified electrode were studied，and the modified electrode exhibits good electrochemical activity and ECL response.Based on the obvious electrochemiluminescence sensitization effect of levofloxacin with Ru（bpy）2+3 in 0.1mol/L phosphate buffer，a new electrochemiluminescence method for the determination of levofloxacin hydrochloride was developed.Under the optimum condition，the calibration curve showed a good linearity with levofloxacin concentration in the range of 1.0×10-7-1.0×10-4 mol/L（r2=0.998 4） and the detection limit（S/N=3） was 1.59 ×10-9 mol/L.The RSD for 10 times determination of 2.2×10-5 mol/L levofloxacin was 3.6 %.The recoveries were in the range of 95.6%-103.5% and the RSD（n=5） was 3.0 %.The proposed method showed high selectivity，sensitivity and simplicity.This method was applied in the analysis of levofloxacin hydrochloride tablet with satisfactory results.关键词：electroehemilumineseence;Ru（bpy）2+3;silica sol;ionic liquid;levofloxacin
- 2680
- |
- 1087
- |
- 1
发布时间： - 摘要：A novel dispersive liquid-liquid microextraction based on solidification of floating organic droplets（DLLME-SFO） combined with gas chromatography（GC） was developed,and validated in the pretreatment and determination of four phthalate esters（PAEs），including dibutyl phthalate，benzyl butyl phthalate，2-ethylhexyl phthalate，and di-n-octyl phthalate in lotion.The experimental conditions affecting extraction efficiencies for the analytes，such as extraction solvent volume，kind of dispersive solvent，dispersive solvent volume，extraction time，pH value and salt concentration were investigated.In the optimal DLLME-SFO method，the sample solution adjusted to pH 3.0 was prepared as a mixed solution of lotion-pure water（1∶10）.15 μL 1-dodecanol（extraction solvent） and 1 300 μL ethanol（dispersive solvent） were rapidly injected into the sample solution.After vortexed for 1 min and centrifugated at 4 000 r? min-1 for 5 min，the sample was cooled down in an ice bath till 1-dodecanol became solid and formed a small ball.Then the solidified 1 dodecanol phase was transferred,and directly detected by GC method after it melted.As results，the linear ranges of the target PAEs were in the range of 5.0-500.0 μg? L-1.The detection limits ranged from 0.001 μg? L-1 to 1.0 μg? L-1.The recoveries were in the range of 88%-108%with relative standard deviations of 1.6%-3.3%.The enrichment factors for the target analytes ranged from 800 to 1 578.Compared with the other pretreatment methods for the extraction of PAEs，the developed method was simple，rapid，sensitive and accurate，and could be applied in the analysis of phthalate esters in lotion.关键词：dispersive liquid-liquid microextraction based on solidification of floating organic droplet（DLLME-SFO）;gas chromatography（GC）;phthalate esters（PAEs）;lotion
- 2388
- |
- 1294
- |
- 9
发布时间： - 摘要：A method for the determination of carbon tetrachloride（CCl4）in refined titanium tetrachloride（TiCl4）by gas chromatography with ECD after hydrolysis under acid suppression was developed.Hydrolysis reactions were carried out according to the ratio（S/V）of TiCl4 to the hydrolysis solution（2 mol/L HCl）as 1∶5,and CCl4 in hydrolysis solutions was extracted with nonane.The results showed that CCl4 added to hydrolysis solutions of high pure TiCl4 could be almost extracted with recoveries of 92.3%-101%,and the HCl concentration in range of 0.85-6 mol/L presented no effects on extracted recoveries.Furthermore,hydrolysis solutions could maintain the stable condition of clarifying while S/V≤1∶4.The recoveries of CCl4 added to high pure TiCl4 were in the range of 87.6%-115% with RSDs of 4.2%-8.5%.The method showed good accuracy and stability.The quantitation limit of the method for 5 mL refined TiCl4 sample was 6.80 μg/L,which was far below the limited value of foreign advanced standards for CCl4 in refined TiCl4.关键词：titanium tetrachloride;carbon tetrachloride;gas chromatography;suppression hydrolysis
- 2320
- |
- 1031
- |
- 0
发布时间： - 摘要：In order to determine the residue of cyproheptadine hydrochloride（CYP）in swine urine,an internal standard method,namely dispersive liquid-liquid micro extraction/ultra performance liquid chromatography-tandem mass spectrometric（UPLC-MS/MS）method,was established.5 mL swine urine was adjusted to pH 11.0 by 5% aquous ammonia.The sample was extracted with 2 mL chloroform（extractant）-isopropyl alcohol（dispersant）by a ratio of 5∶3.The extractant was separated by 8 000 r/min centrifugation in 4 ℃,and evaporated with nitrogen at 50 ℃.The residue was dissolved with 1 mL 0.1% formic acid∶acenitril（80∶20）and detected by UPLC-MS using diphenylpyraline hydrochloride as an internal standard,with positive electrospray ionization under multi-reaction monitoring mode.The results showed that the linear range of CYP was in the range of 0.5-25 μg/L with a correlation coefficient of 0.999 5.The LOD of the method was 0.05 μg/L,while the LOQ was 0.1 μg/L.The recoveries of cyproheptadine hydrochloride at spiked range of 0.1-5.0 μg/L were in the range of 90.2%-109.7% with RSDs no more than 8.5%.The method showed good accuracy and precision.关键词：cyproheptadine hydrochloride;diphenylpyraline hydrochloride;ultra performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）;internal standard method;dispersive liquid-liquid micro extraction（DLLME）
- 2667
- |
- 1377
- |
- 2
发布时间： - 摘要：The water-soluble CdTe /ZnS core-shell quantum dots（QDs） were synthesized using thioglycolic acid（TGA） as stabilizer．It was found there is an appreciable over lap between the emission spectrum of CdTe /ZnS QDs and the absorption spectrum of malachite green（MG）.Moreover，the interaction（mainly the electrostatic force） between the electronegative CdTe QDs and cation dye MG can draw them close.Thus，the fluorescence resonance energy transfer（FRET） system was constructed between CdTe /ZnS QDs（donor） and MG（acceptor）.Based on this FRET system，a sensitive method for the determination of MG was developed.Effects of experimental conditions were investigated.The optimal conditions were as follows：buffer:pH 8.0 Tris-HCl solution，concentration of quantum dots：1.6×10-4 mol/L，reaction time:20 min，reaction temperature：30 ℃.Under the optimal conditions，a good linearity was obtained between the quenched fluorescence intensity of CdTe /ZnS QDs and concentration of MG in the range of 0.048-3.2 μmol/L.The correlation coefficient was 0.999 3 and the limit of detection（3σ） was 0.015 8 μmol/L.The proposed method was successfully applied in the determination of MG in water samples with spiked recoveries of 99.3%-102 %.Furthermore，the possible mechanism of interaction between CdTe/ZnS QDs and MG was discussed.关键词：CdTe/ZnS quantum dots;fluorescence resonance energy transfer;fluorescence quenching;malachite green
- 2134
- |
- 1315
- |
- 5
发布时间： - 摘要：In this study,several sulfur-terpyridines and ruthenium complexes designed for development of new reusable ECL sensor were characterized by electrospray multi-stage tandem mass spectrometry（ESI-MSn）with direct injection,and their cleavage fragments and fragmentation pathways under ESI conditions were analyzed.The results showed that the sulfur-terpyridine derivatives are readily protonated by positive-ion ESI-MS and the carbon-sulfur bonds of sulfur-terpyridine derivatives are easy to break during the process of positive mode of ESI-MS.Also,the cleavage ways of carbon-sulfur bonds are different.The terpyridyl ligands containing arylthio firstly decomposed from the carbon-sulfur bond attached to the aromatic carbon-sulfur bond and lost some non-sulfur fragments while the terpyridyl ligands containing benzylthio broke from the benzylic carbon-sulfur bond and lost some fragments containing sulfur.The complexes of sulfur-terpyridyl ruthenium are easy to be detected by ESI-MS in positive mode.These complexes are stable and not easy to decompose in multi-stage mass fracture.Through identification of molecular ion peaks and further comparison of isotope mass peaks with the simulation value,the structures of complexes were identified.This research not only shows that ESI-MS is simple and accurate，and is suitable to study the structures of sulfur-terpyridine ligands and corresponding ruthenium complexes,but also provides a reference for study on the structures of this kind of compounds.关键词：terpyridine ruthenium;electrospray-tandem mass spectrometry;electrochemiluminescence（ECL）reagent;sulfur
- 2224
- |
- 1185
- |
- 1
发布时间： - 摘要：The filtration of released components in the mainstream cigarette smoke by adding graphene oxide（GO） modified activated carbon fiber（ACF） into the cigarette filter was studied.The materials were characterized by scanning electron microscope（SEM），X-ray powder diffraction（XPS） and surface area measurements.The results showed that GO was coated on ACF uniformly.Compared with ACF，the binding energy of O1s in GO-ACF became lower and the peak became more smooth，also，the surface area and the total pore volume increased.Adding GO-ACF to the cigarette filter could result in its contents of phenol，hydrocyanic acid，aldehydes and ketones all lower than those in the ACF filter cigarettes，in which the contents of components all decreased by at least 10% except for aldehyde，and the reductions of phenol and crotonaldehyde were up to 26.7% and 33.1%，respectively.The study on the mechanism of the filtration indicated that，after modifying GO onto ACF，the active sites increased，since the material surface became rich in hydroxyl，carboxyl，carbonyl and conjugated groups which could interact with conjugated or polar molecules easily.This method was effective，and laid a foundation for the application of two dimensional nano materials，such as GO，in cigarette science.关键词：GO;cigarette mainstream smoke;ACF;released component
- 2497
- |
- 1250
- |
- 6
发布时间： - 摘要：Gallic aldehyde was heated up by thermogravimetry from room temperature to 700 ℃ at different heating rates（5，10，15， 20 ℃/min） under nitrogen atmosphere while its DSC curve was obtained by differential scanning calorimetry at 10 ℃/min.The thermal decomposition mechanism was inferred in accordance with its weight loss and molecular structure while kinetic parameters in thermal equilibrium and original reaction conditions were calculated by double extrapolated method.Experimental results showed that after the volatilization of unbound and bound water，one molecule CO was lost due to the cracking of the aldehyde group.The decomposition reaction of gallic aldehyde was pushed to high temperatures with the increase of heating rates，and the maximum weight loss rate decreased in turn.The activation energy（Eα） of pyrolysis was 286.21 kJ/mol while pre-exponential factor（lnA） was 70.21.The pyrolysis mechanism function was g（α）=［-ln（1-α）］2/3 with reaction order（n） of 2/3.Pyrolysis activation energy decreased with the increase of conversion ratio.According to its kinetic parameters，the shelflives of gallic aldehyde was 4-5 years at room temperature.关键词：gallic aldehyde;TG-DTG technique;double extrapolated method;thermal stability;thermal decomposition kinetics
- 2321
- |
- 1050
- |
- 2
发布时间： - 摘要：A method was developed for the determination of 11 perfluorinated compounds (PFCs) (e.g.perfluorobutanesulfonate,perfluorohexane-sulfonate,perfluoroheptanoic-acid,perfluorooctanoate,perfluorooctane-sulfonate,perfluorononanoic-acid,perluorodecanoic-acid,perfluoroundecanoic-acid,perfluorodecanesulfonate,perfluorododecanoic-acid and perfluorotetradecanoic acid)in meat by ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) with solid phase extraction column.After added with the isotopic labeled sodium perfluoro-1-［1,2,3,4,-13C4］octanesulfonat (MPFOA) and perfluoro-n-［1,2,3,4,-13C4］octanoic acid (MPFOS),the samples were extracted and homogenized with acetonitrile,and then suction filted through glass fiber and defatted with n-hexane by liquid-liquid extraction method.The extract was purified with Waters Oasis HLB solid phase extraction column,and concentrated with N2.The perfluorinated compounds were separated with UPLC using a mixture of 2 mmol/L ammonium acetate-2 mmol/L ammonium acetate methanol solution as mobile phase,and analysed by UPLC-MS/MS ESI(-) under MRM mode with the internal standard method.The calibration curves were linear in the range of 0.50-20.0 μg/L for 11 PFCs.The limits of detection for the method (LODs) were between 0.014 μg/kg and 0.060 μg/kg,and the limits of quantitation were between 0.047 μg/kg and 0.199μg/kg.The mean recoveries were in the range of 70.9%-107.1%,with relative standard deviations (RSDs,n=6) of 0.4% -11.4%.This method was suitable for the identification and quantification of 11 perfluorinated compounds in meat due to its simplicity,accuracy and high sensitivity.关键词：perfluorinated compounds;meat;ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS);solid phase extraction
- 2467
- |
- 1196
- |
- 11
发布时间： - 摘要：The interaction between I-3 and malachite green（MG）and its application for determining trace dopamine by resonance light scattering（RLS）method were studied.It was found that malachite green could react with I-3 to form an ion-association complex（MG（I3）2）with the composition ratio of 1∶2 by electrostatic forces in citric acid–sodium citrate buffer solution（ pH 4.5）,in the presence of polyvinyl alcohol（PVA）and p-octyl polyethylene glycol phenyl ether（OP）.Dopamine could convert I-3 to I-,resulting in the decrease of resonance light scattering intensity of the malachite green-I-3 system.Based on this,a new simple method with high sensitivity and good repeatability was developed to determine dopamine by resonance light scattering.Under the optimal conditions,the calibration curve was linear in the range of 2.0×10-7-4.5×10-6 mol?L-1,with a correlation coefficient of 0.999 1 and a detection limit（3S/k）of 9.5×10-8 mol?L-1.The proposed method was used to determine dopamine in injection and human serum samples with mean recoveries of 100.1%-102.4% and relative standard deviations of 0.41%-4.8%.关键词：dopamine;malachite green;I-3;resonance light scattering
- 2056
- |
- 1089
- |
- 2
发布时间： - 摘要：A chitosan/glutathione composite film combined with glucose oxidase was employed to fabricate an amperometric glucose biosensor.The enzyme electrode was characterized by cyclic voltammetry.The experimental results showed that，chitosan and glutathione composite film can assist in electron transfer，improve response electrode current.Using orthogonal table L9（34） experiment design，the best experimental conditions were obtained by visual analysis.Under the optimized conditions，the sensor has a good linear relationship with concentration of glucose solution in the range of 1-18 mmol/L，the detection limit is 1.3 mmol/L.Experiments showed that，this sensor has the advantages of fast response，good stability and selectivity,and is suitable for the determination of glucose in urine sample.关键词：gold electrode;chitosan;GOx;biosensor;glutathione;orthogonal array
- 2189
- |
- 1148
- |
- 3
发布时间： - 摘要：A method was developed for the determination of conjugated linoleic acid（CLA） in sesame by hollow fiber based two-phase liquid phase microextraction（LPME） coupled with high performance liquid chromatography（HPLC）.For LPME， effects of pH value of extraction solvent，extraction time and stirring rate were investigated，and the optimum experimental conditions were as follows：pH value of extraction solvent（KOH solution）：11.0， extraction time：30 min， stirring rate：1 000 r/min.The qualitative and quantitative analysis of CLA were performed by HPLC method.The proposed method provided a wide linear range with a correlation coefficient（r2） of 0.993，a-detection limit（S/N=3） of 17 μg/L.The relative standard deviation（RSD，n=6） was 4.9% and the enrichment factor of CLA was 12.4. The recoveries of CLA in three kinds of sesame ranged from 81.4% to 94.8%.The method is simple and effective in the determination of CLA in plant，and could also be used in the determination of CLA in the other complex matrix samples such as dairy products，vegetable oils，etc.关键词：Key words：hollow fiber;two phase liquid-phase microextraction;high performance liquid chromatography;sesame;conjugated linoleic acid
- 1966
- |
- 1106
- |
- 3
发布时间： - 摘要：A novel method for the determination of ferulic acid was developed based on its inhibition effect on the luminol-H2O2-silver nanoparticles chemiluminescence system.Various factors influencing the chemiluminescence system were investigated and the possible mechanism was also studied.Under the optimum conditions,the linear range for the determination of ferulic acid was from 1.0×10-8 to 4.0×10-5 mol/L with a detection limit（3σ） of 2.0×10-9 mol/L.The relative standard deviation was 2.3% for 2.0×10-7 mol/L ferulic acid solution in nine repeated measurements.The proposed method was applied in the determination of ferulic acid in Taitai Beauty samples with satisfactory results.关键词：chemiluminescence;Ag nanoparticles;luminol;ferulic acid
- 2527
- |
- 1119
- |
- 1
发布时间： - 摘要：A liquid chromatography-tandem mass spectrometric（LC-MS/MS） method for the determination of corticosterone and hydrocortisone in serum was developed.The fat in serum was removed with hexane and extracted with methyl ether.Corticosterone and hydrocortisone were separated on an Agilent Eclipse Plus-C18 column（150 mm×2.1 mm，3.5 μm） and detected by chromatography coupled with tandem mass spectrometry in positive ion mode with mobile phase of acetonitrile-0.1% formic acid（containing 0.01 mol/L ammonium formate）.The flow rate of mobile phase was set at 0.3 mL/min.The calibration curves of two target compounds were in the range of 0.5-200 ng/mL，with correlation coefficients（r2） of 0.999 7 and 0.999 4，respectively.The recoveries for the spiked sample at the levels of 5.0，25.0 and 75.0 ng/mL for corticosterone and 0.5，2.5,10.0 ng/mL for hydrocortisone，ranged from 86.6 % to 102.7% with relative standard deviations not more than 7.1%.The limits of detection（S/N=3） for corticosterone and hydrocortisone were 0.1 ng/mL and 0.05 ng/mL，respectively.This method was simple，sensitive and accurate，and was suitable for the determination of corticosterone and hydrocortisone in serum sample.关键词：serum;liquid chromatography tandem mass spectrometry;corticosterone;hydrocortisone
- 1991
- |
- 1260
- |
- 2
发布时间： - 摘要：Based on the improved jet type electrochemiluminescence (ECL) flow injection system,a sensitive method for the determination of melamine in milk power and milk was developed.The experimental conditions of the proposed method,for example pH value,flow rate,injection volume,scan rate and concentration of Ru(bpy)2+3 were optimized.The best results were achieved under the following conditions:running buffer:0.1 mol/L pH 9.5 phosphate buffer,detection reagent:2.5×10-4 mol/L Ru(bpy)2+3,flow rate:20 μL/s,injection volume:100 μL,scan rate:50 mV/s.Under the optimized conditions,the ECL intensity was proporational to the negative logarithmic concentration of melamine in the range of 1.0×10-9-1.0×10-3g/L.The detection limit(S/N=3) was 1.0×10-9 g/L.The recoveries of melamine in milk power and milk at various spiked levels were in the range of 92.2%-114.2% with relative standard deviations (RSDs ) of 0.46%-1.2%The proposed method,with the advantages of sensitivity,easy to operation,and low sample consumption,is expected to be used for the rapid detection of melamine on spot.关键词：jet type;flow detection cell;electrochemiluminescence;melamine
- 1998
- |
- 1116
- |
- 4
发布时间： - 摘要：A high-performance liquid chromatographic（HPLC） method for the determination of relative substances in thioctic acid tablets was developed.The separation of analyte was performed on a Waters XBridge column（5 μm，150 mm×4.6 mm） with phosphate buffer（pH value was adjusted to 2.5 with phosphoric acid）-acetonitrile-methanol（50∶45∶5） as mobile phase，at a flow rate of 1.0 mL/min and an injection volume of 20 μL.The photo-diode array detector（PDA） was set at 220 nm，with full scan range of 200-400 nm.The column temperature was ambient.Under the above chromatographic conditions，the calibration curve was linear（r=0.999 9） in thioctic acid concentration range of 0.4-20.0 mg/L.The limit of detection（LOD） for thioctic acid was 0.2 mg/L and the limit of quantitation（LOQ） was 0.6 mg/L.The relative standard deviation（RSD，n=12） was 3.4%,and the average spiked recovery was 100.9% with RSD of 2.0%.The proposed method could be applied in the determination of relative substances in thioctic acid tablets with the advantages of simplicity，rapidity，accuracy，good selectivity and high sensitivity.关键词：thioctic acid tablet;thioctic acid;degradation products;HPLC
- 2125
- |
- 1166
- |
- 0
发布时间： - 摘要：A two-step microreactor was designed,and the influence of geometry parameters on reaction was optimized.To improve hybrid in the mix channel of the microreactor,the rib obstacles that can induce chaotic convection were designed.The ratio of height of obstacle and channel,the ratio of width of obstacle and spacing,and the width of obstacle were optimized with the software based on finite element theory.The serpentine channel was chose as the reaction unit of the microreactor,and the influences of the channel length,reaction time and initial concentration on reaction were investigated.Furthermore,a two-step microreactor for oxidation of glucose was designed.关键词：microreactor;micro-mixing unit;structural design;numerical calculation
- 2006
- |
- 1178
- |
- 1
发布时间： - 摘要：Organic reference materials（RMs） have been widely used in the spectrum analysis fields.The certified techniques for chemical purity of organic RMs are key factors for the certification of RMs.One kind of the certification techniquec for organic RMs is the direct method，which can give the certified value by measuring the main component.The direct methods include gas chromatography（GC），liquid chromatography（LC），quantity nuclear magnetic resonance（qNMR），elemental analysis（EA） and titration method（mass titration and volumetric titration）.The other one is the indirect method，which certify the value by substracting the impurities from the total content，such as freezing point depression（FPD），differential scanning calorimetry（DSC），coupled with water determination，residual solvent measurement and inorganic impurities determination.This paper summarized the certification methods for organic RMs with high purity（2000-2011），compared the advantages and disadvantages of these techniques,and also gave an outlook for the development of certification method for organic RMs in the future.关键词：organic RMs;chemical purity;certified technique;gas chromatography（GC）;liquid chromatography（LC）;quantity nuclear magnetic resonance（qNMR）;freezing point depression;differential scanning calorimetry（DSC）;review
- 2478
- |
- 3
- |
- 15
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