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2016 Volume 44 Issue 2
2016, 44(2): 173-178
doi: 10.11895/j.issn.0253-3820.150602
Abstract:
A method was developed for the in situ analysis of magnesium isotopes by femtosecond laser ablation multi-collector inductively coupled mass spectrometry (fsLA-MC-ICP-MS). Concentration matching experiment revealed that the Mg isotopic composition could be measured accurately when Mg concentration difference between sample and standard was in the range of 0.4-3.0. The Mg isotopic composition was affected by the femtosecond laser conditions, including laser spot size and scanning speed, due to mass discrimination changing which was caused by different mass loading into mass spectrometer. The amount of ablated aerosol was correlated with laser frequency, laser ablation spot size, scanning speed. However, the laser energy density showed negligible effect on the accuracy of Mg isotope measurement due to the high energy output of femtosecond which was higher than the ablation threshold. To obtain reliable Mg isotopic compositions, the laser ablation spot size, laser frequency and scanning speed should be consistent during one analytical section and the difference of Mg concentration between standard and samples should be in 3 times. The analytical results of two reference materials agreed well with the published values within 2 s analytical uncertainties. The developed method is simple, reliable and accurate, and can be used for the Mg isotope analysis of volcanic glasses and silicate minerals.
A method was developed for the in situ analysis of magnesium isotopes by femtosecond laser ablation multi-collector inductively coupled mass spectrometry (fsLA-MC-ICP-MS). Concentration matching experiment revealed that the Mg isotopic composition could be measured accurately when Mg concentration difference between sample and standard was in the range of 0.4-3.0. The Mg isotopic composition was affected by the femtosecond laser conditions, including laser spot size and scanning speed, due to mass discrimination changing which was caused by different mass loading into mass spectrometer. The amount of ablated aerosol was correlated with laser frequency, laser ablation spot size, scanning speed. However, the laser energy density showed negligible effect on the accuracy of Mg isotope measurement due to the high energy output of femtosecond which was higher than the ablation threshold. To obtain reliable Mg isotopic compositions, the laser ablation spot size, laser frequency and scanning speed should be consistent during one analytical section and the difference of Mg concentration between standard and samples should be in 3 times. The analytical results of two reference materials agreed well with the published values within 2 s analytical uncertainties. The developed method is simple, reliable and accurate, and can be used for the Mg isotope analysis of volcanic glasses and silicate minerals.
2016, 44(2): 179-185
doi: 10.11895/j.issn.0253-3820.150319
Abstract:
Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were prepared by co-precipitation method, which possessed intrinsic peroxidase-like activity. It was found that the as-prepared Fe3O4 MNPs could not only catalyze the oxidation of peroxidase substrate, diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by H2O2 to produce the colored product with maximum absorbance at 417 nm, but also catalyze the oxidation of 2,4-dinitrotoluene (DNT) by H2O2 and thus consume H2O2 in the reaction system. On the basis of the reaction described above, a novel colorimetric reaction system based on Fe3O4 MNPs-ABTS-H2O2-DNT was established for determination of trace amount of DNT. Some key influencing factors of the proposed Fe3O4 MNPs-ABTS-H2O2-DNT system were systematically discussed and optimized. Under the optimal conditions, the absorbance of the system at 417 nm displayed a good linear response with DNT concentration in the range from 5×10-7 to 2.0×10-5 mol/L with a detection limit of 1.5×10-7 mol/L (S/N=3). These results demonstrated that the constructed colorimetric method was simple, rapid and sensitive enough for colorimetric detection of DNT, which would have a great potential in the application of on-line monitoring of DNT in environmental water samples.
Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were prepared by co-precipitation method, which possessed intrinsic peroxidase-like activity. It was found that the as-prepared Fe3O4 MNPs could not only catalyze the oxidation of peroxidase substrate, diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by H2O2 to produce the colored product with maximum absorbance at 417 nm, but also catalyze the oxidation of 2,4-dinitrotoluene (DNT) by H2O2 and thus consume H2O2 in the reaction system. On the basis of the reaction described above, a novel colorimetric reaction system based on Fe3O4 MNPs-ABTS-H2O2-DNT was established for determination of trace amount of DNT. Some key influencing factors of the proposed Fe3O4 MNPs-ABTS-H2O2-DNT system were systematically discussed and optimized. Under the optimal conditions, the absorbance of the system at 417 nm displayed a good linear response with DNT concentration in the range from 5×10-7 to 2.0×10-5 mol/L with a detection limit of 1.5×10-7 mol/L (S/N=3). These results demonstrated that the constructed colorimetric method was simple, rapid and sensitive enough for colorimetric detection of DNT, which would have a great potential in the application of on-line monitoring of DNT in environmental water samples.
2016, 44(2): 186-191
doi: 10.11895/j.issn.0253-3820.150728
Abstract:
High precise determination of stable bromine isotopic ratios was carried out by thermal ionization mass spectrometer triton with 8 kV accelerating voltage using static multicollection of Cs2Br+ ions. The effect of B and Cl content on the measurement of bromine isotope was studied. The static multicollection method has many advantages, such as, high precision (external accuracy lies between 0.09‰-0.18‰), small amount of sample loading (10-20 μg Br) and short acquisitiotest time (just 8 min for 100 data acquisition). The results showed that the effect of Cl on the measurement of Br isotope ratio increased with the increase of Cl content, and that the presence of B made the determined bromine isotope ratio lower than that without B. The effect of the sample loading sequence on the results of the determined Br isotopic ratio was insignificant. Meanwhile, the Br isotopic composition of four bromide was determined, its δ81Br was between 0.61‰ and 1.68‰, showing a significant bromine isotope fractionation.
High precise determination of stable bromine isotopic ratios was carried out by thermal ionization mass spectrometer triton with 8 kV accelerating voltage using static multicollection of Cs2Br+ ions. The effect of B and Cl content on the measurement of bromine isotope was studied. The static multicollection method has many advantages, such as, high precision (external accuracy lies between 0.09‰-0.18‰), small amount of sample loading (10-20 μg Br) and short acquisitiotest time (just 8 min for 100 data acquisition). The results showed that the effect of Cl on the measurement of Br isotope ratio increased with the increase of Cl content, and that the presence of B made the determined bromine isotope ratio lower than that without B. The effect of the sample loading sequence on the results of the determined Br isotopic ratio was insignificant. Meanwhile, the Br isotopic composition of four bromide was determined, its δ81Br was between 0.61‰ and 1.68‰, showing a significant bromine isotope fractionation.
2016, 44(2): 192-197
doi: 10.11895/j.issn.0253-3820.150600
Abstract:
An efficient extraction and purifying method coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS) with electron impact (EI) detection was developed to determine eight organophosphate esters (OPEs) in sediment samples. The selected OPEs were extracted twice from the sediments through vortex oscillation and ultrasonic extraction using 20 mL of n-hexane and acetone mixture (1:1, V/V) for 10 min. Further purification by Florisil solid phase extraction (SPE) column, elution by 8 mL of ethyl acetate, concentration, and solvent exchanges for n-hexane were carried out. All target compounds were separated using the DB-5ms capillary column (30 m×0.25 mm×0.25 μm) and detected by tandem mass spectrometry with selected reaction monitoring, and determined by the internal standard method. The result showed that this pretreatment method was simple with less solvent consumption. At three spiked levels of 10, 20 and 50 μg/L, the recovery of selected OPEs (except TEP) was 80% to 120%, and the limit of detection was 0.31-64.5 ng/L, showing a good precision and accuracy.
An efficient extraction and purifying method coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS) with electron impact (EI) detection was developed to determine eight organophosphate esters (OPEs) in sediment samples. The selected OPEs were extracted twice from the sediments through vortex oscillation and ultrasonic extraction using 20 mL of n-hexane and acetone mixture (1:1, V/V) for 10 min. Further purification by Florisil solid phase extraction (SPE) column, elution by 8 mL of ethyl acetate, concentration, and solvent exchanges for n-hexane were carried out. All target compounds were separated using the DB-5ms capillary column (30 m×0.25 mm×0.25 μm) and detected by tandem mass spectrometry with selected reaction monitoring, and determined by the internal standard method. The result showed that this pretreatment method was simple with less solvent consumption. At three spiked levels of 10, 20 and 50 μg/L, the recovery of selected OPEs (except TEP) was 80% to 120%, and the limit of detection was 0.31-64.5 ng/L, showing a good precision and accuracy.
2016, 44(2): 198-204,272
doi: 10.11895/j.issn.0253-3820.150535
Abstract:
To determine the seed vigor of coffee quickly and non-destructively, surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) was used to obtain chemical fingerprints directly from the surface of the coffee seed, without any sample pretreatment. The mass spectral raw data were analyzed by multivariate analysis, including principal component analysis (PCA), cluster analysis (CA) and discriminant analysis (DA), to differentiate efficaciously the coffee seeds with different vigor. The experimental results demonstrated that in the positive ion mode, DAPCI-MS combined with multivariate analysis could effectively distinguish different seed vigor for coffee seed. Three principal components were extracted by PCA, and their cumulative contribution rate was 92.2%. Coffee seeds with the same vigor was packed closely together in CA analysis, and its accuracy was 100%. In DA analysis, the return discriminant ratio for the training muster was as high as 100%, while the cross validation analysis success rate was 100%. Thus, it was concluded that the coffee seeds with different vigor could be differentiated by DAPCI-MS, and the results provided a basis for establishing a fast, non-destructive and sensitive detection method of seed vigor.
To determine the seed vigor of coffee quickly and non-destructively, surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) was used to obtain chemical fingerprints directly from the surface of the coffee seed, without any sample pretreatment. The mass spectral raw data were analyzed by multivariate analysis, including principal component analysis (PCA), cluster analysis (CA) and discriminant analysis (DA), to differentiate efficaciously the coffee seeds with different vigor. The experimental results demonstrated that in the positive ion mode, DAPCI-MS combined with multivariate analysis could effectively distinguish different seed vigor for coffee seed. Three principal components were extracted by PCA, and their cumulative contribution rate was 92.2%. Coffee seeds with the same vigor was packed closely together in CA analysis, and its accuracy was 100%. In DA analysis, the return discriminant ratio for the training muster was as high as 100%, while the cross validation analysis success rate was 100%. Thus, it was concluded that the coffee seeds with different vigor could be differentiated by DAPCI-MS, and the results provided a basis for establishing a fast, non-destructive and sensitive detection method of seed vigor.
2016, 44(2): 205-211
doi: 10.11895/j.issn.0253-3820.150549
Abstract:
In this paper, polyethylenimine functionalized magnetic nanoadsorbents (Fe3O4-PEI) were prepared based on the chemical crosslinking reaction using glutaraldehyde as the crosslinker at room temperature. The structure of the nanomaterial was characterized by TEM, XRD, FT-IR, VSM, TGA and so on. Three anionic dyes (alizarin red, nuclear fast red and alizarin green) with anthraquinone structures were chosen as the target adsorbates. The parameters (such as solution pH, adsorption time, initial concentration of dyes and operating temperature) probably affecting the adsorption behaviour as well as the adsorption kinetics and isotherms were investigated by static adsorption experiments. The results indicated that under the experimental pH of 3.0, the qmax of alizarin red, nuclear fast red and alizarin green at 303 K was 256.1, 138.8 and 134.6 mg/g, respectively; initial dye concentration and contact time had significant effect on adsorption efficiency of target dyes; the adsorption equilibrium could reach within 60 min, the pseudo-secon-dorder kinetics model and the Langmuir isotherm equations could better describe the adsorption process; and the thermodynamics suggested an endothermic and spontaneous process for the adsorption of anthraquinone dyes. In addition, the remarkable stability and reusability of Fe3O4-PEI makes it a promising adsorbent for treatment of dye-bearing wastewater.
In this paper, polyethylenimine functionalized magnetic nanoadsorbents (Fe3O4-PEI) were prepared based on the chemical crosslinking reaction using glutaraldehyde as the crosslinker at room temperature. The structure of the nanomaterial was characterized by TEM, XRD, FT-IR, VSM, TGA and so on. Three anionic dyes (alizarin red, nuclear fast red and alizarin green) with anthraquinone structures were chosen as the target adsorbates. The parameters (such as solution pH, adsorption time, initial concentration of dyes and operating temperature) probably affecting the adsorption behaviour as well as the adsorption kinetics and isotherms were investigated by static adsorption experiments. The results indicated that under the experimental pH of 3.0, the qmax of alizarin red, nuclear fast red and alizarin green at 303 K was 256.1, 138.8 and 134.6 mg/g, respectively; initial dye concentration and contact time had significant effect on adsorption efficiency of target dyes; the adsorption equilibrium could reach within 60 min, the pseudo-secon-dorder kinetics model and the Langmuir isotherm equations could better describe the adsorption process; and the thermodynamics suggested an endothermic and spontaneous process for the adsorption of anthraquinone dyes. In addition, the remarkable stability and reusability of Fe3O4-PEI makes it a promising adsorbent for treatment of dye-bearing wastewater.
2016, 44(2): 212-217
doi: 10.11895/j.issn.0253-3820.150744
Abstract:
A kind of molecular imprinted polymer (MIP) was synthesized by bulk polymerization using guanosine as dummy template molecule. The results of Fourier transform infrared spectrometer (FT-IR) and scanning electron microscope showed that MIP had homogenous and uniform-sized cavities. It was confirmed that MIP had higher binding affinity and selectivity towards gonyautoxins 1,4 (GTX1,4) than NIP according to the static equilibrium adsorption. The solid phase extraction columns were packed with MIP. The maximum recovery (85.05%) of MISPE was achieved using 0.1 mol/L acetic acid as washing solution and ethanol-water (95:5, V/V) as elution solution. Then the concentrations of GTX1,4 from culture solution of Alexandrium minutum and Alexandrium tamarense were determined to be 1.10 and 0.99 μg/L, respectively, under the optimum conditions of washing and elution, and RSD was 3.3% and 4.4%, respectively, indicated good LOD and higher precision.
A kind of molecular imprinted polymer (MIP) was synthesized by bulk polymerization using guanosine as dummy template molecule. The results of Fourier transform infrared spectrometer (FT-IR) and scanning electron microscope showed that MIP had homogenous and uniform-sized cavities. It was confirmed that MIP had higher binding affinity and selectivity towards gonyautoxins 1,4 (GTX1,4) than NIP according to the static equilibrium adsorption. The solid phase extraction columns were packed with MIP. The maximum recovery (85.05%) of MISPE was achieved using 0.1 mol/L acetic acid as washing solution and ethanol-water (95:5, V/V) as elution solution. Then the concentrations of GTX1,4 from culture solution of Alexandrium minutum and Alexandrium tamarense were determined to be 1.10 and 0.99 μg/L, respectively, under the optimum conditions of washing and elution, and RSD was 3.3% and 4.4%, respectively, indicated good LOD and higher precision.
2016, 44(2): 218-223
doi: 10.11895/j.issn.0253-3820.150725
Abstract:
An analytical method for the determination of interaction between pesticide and biological macromolecules (bovine serum albumin (BSA) protein, superoxide dismutase (SOD) enzyme) was developed based on high resolution mass spectrometry. All results revealed that each BSA bonded with maximum five Parathion-methyls after 30 min, and it would not interact with emamectin benzoate. Moreover, each SOD after mixing with corresponding pesticides could bond with two dichlorvos (DDVPs) and one avermectin after 30 min. In addition, there is no interaction between SOD and thifluzamide. The interaction between SOD and avermectin trended stable after 30 min, and similar phenomenon was observed between SOD and DDVP after 20 min. There were certain obvious some differences in the pathway of interactions for BSA and SOD, both of which were bonded with the pesticides, based on time resolved determinations for their bonding process. Finally, we compared the proposed method with standard methods (fluorescence spectrometry, NBT kit method) and molecular docking results, and the reliability of the proposed method was supported. It owned preponderances in less sample consumption, high detection speed, and more capacities compared with traditional strategies. Therefore, the proposed mothed would own certain practical values in either researches and developments or safety evaluations for new pesticides.
An analytical method for the determination of interaction between pesticide and biological macromolecules (bovine serum albumin (BSA) protein, superoxide dismutase (SOD) enzyme) was developed based on high resolution mass spectrometry. All results revealed that each BSA bonded with maximum five Parathion-methyls after 30 min, and it would not interact with emamectin benzoate. Moreover, each SOD after mixing with corresponding pesticides could bond with two dichlorvos (DDVPs) and one avermectin after 30 min. In addition, there is no interaction between SOD and thifluzamide. The interaction between SOD and avermectin trended stable after 30 min, and similar phenomenon was observed between SOD and DDVP after 20 min. There were certain obvious some differences in the pathway of interactions for BSA and SOD, both of which were bonded with the pesticides, based on time resolved determinations for their bonding process. Finally, we compared the proposed method with standard methods (fluorescence spectrometry, NBT kit method) and molecular docking results, and the reliability of the proposed method was supported. It owned preponderances in less sample consumption, high detection speed, and more capacities compared with traditional strategies. Therefore, the proposed mothed would own certain practical values in either researches and developments or safety evaluations for new pesticides.
2016, 44(2): 224-231
doi: 10.11895/j.issn.0253-3820.150537
Abstract:
Magnetic adsorbents have recently been extensively investigated and applied in the field of water purification, because of their magnetic characters which are advantageous for the separation and recycle of these materials. Unfortunately, common magnetic materials are unstable and prone to dissolution in acid environment, thus limiting their practical applications in wide pH range, particularly in acidic condition. Therefore, it is highly imperative to exploit a novel magnetic adsorbent that is acid-resistant, to simplify the separation process during the water purification. In the present work, an acid-resistant magnetic Co/C nanocomposite was synthesized by using ZIF-67 as both template and precursor. The ZIF-67 was carbonized in an argon atmosphere at 800℃ for 1 hour, and then treated with acid. Upon calcination at appropriate temperature in inert atmosphere, the generated Co nanoparticles were uniformly wrapped by graphite layers, due to the graphitization of carbon upon the catalysis effect of Co. The formed graphite layers were able to protect the Co particles from oxidation and acid environment, thus resulting in the generation of an acid-resistant magnetic adsorbent that could be applied in a wide pH range (pH 1-13). Remarkably, the as-synthesized magnetic Co/C nanocomposite demonstrated excellent adsorption performance towards two typical organic dyes (Rhodamine B and malachite green) over a wide pH range. The adsorption isotherms of Rhodamine B and malachite green on Co/C nanocomposite were well fitted with the Langmuir model. Impressively, the maximum adsorption capacities towards Rhodamine B and malachite green were estimated to be 400 mg/g and 561.8 mg/g, respectively, far exceeding many previously reported adsorbents. Moreover, the adsorbent could be easily regenerated by washing with ethylene glycol (EG), suggesting its excellent reusability. Even after 5 cycles of reuse, no obvious capacity degradation was observed. Furthermore, practical application of the magnetic adsorbent was demonstrated by the removal of organic dyes from domestic wastewater with a superior removal efficiency of higher than 97%.
Magnetic adsorbents have recently been extensively investigated and applied in the field of water purification, because of their magnetic characters which are advantageous for the separation and recycle of these materials. Unfortunately, common magnetic materials are unstable and prone to dissolution in acid environment, thus limiting their practical applications in wide pH range, particularly in acidic condition. Therefore, it is highly imperative to exploit a novel magnetic adsorbent that is acid-resistant, to simplify the separation process during the water purification. In the present work, an acid-resistant magnetic Co/C nanocomposite was synthesized by using ZIF-67 as both template and precursor. The ZIF-67 was carbonized in an argon atmosphere at 800℃ for 1 hour, and then treated with acid. Upon calcination at appropriate temperature in inert atmosphere, the generated Co nanoparticles were uniformly wrapped by graphite layers, due to the graphitization of carbon upon the catalysis effect of Co. The formed graphite layers were able to protect the Co particles from oxidation and acid environment, thus resulting in the generation of an acid-resistant magnetic adsorbent that could be applied in a wide pH range (pH 1-13). Remarkably, the as-synthesized magnetic Co/C nanocomposite demonstrated excellent adsorption performance towards two typical organic dyes (Rhodamine B and malachite green) over a wide pH range. The adsorption isotherms of Rhodamine B and malachite green on Co/C nanocomposite were well fitted with the Langmuir model. Impressively, the maximum adsorption capacities towards Rhodamine B and malachite green were estimated to be 400 mg/g and 561.8 mg/g, respectively, far exceeding many previously reported adsorbents. Moreover, the adsorbent could be easily regenerated by washing with ethylene glycol (EG), suggesting its excellent reusability. Even after 5 cycles of reuse, no obvious capacity degradation was observed. Furthermore, practical application of the magnetic adsorbent was demonstrated by the removal of organic dyes from domestic wastewater with a superior removal efficiency of higher than 97%.
2016, 44(2): 232-240
doi: 10.11895/j.issn.0253-3820.150635
Abstract:
The yeast Pichia pastoris is an effective host for recombinant protein production and the recombinant protein production level is tightly related to the concentrations of intracellular metabolites. The intracellular metabolites have the features of wide range of types, distinct variation in physical and chemical properties, rapid turning-over and low concentration, so it is difficult to quantify their concentrations precisely. In this experiment, we tried to make it possible by combining ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry and 13C isotope labeling techniques. 64 metabolites including organic acids, sugar phosphate, nucleoside substance, amino acid were successfully separated by UPLC with three kinds of chromatography column. The appropriate and unique ion pairs and collision voltages were found after the mass spectrometry condition optimization. By using the U13C metabolites as internal standards collected from the cells growing on U13C-glucose as sole carbon source, the standard curves of 53 metabolites were established. The results showed that the method presented here had a high accuracy. The correlation coefficients were above 0.99. The method also had a good reproducibility, and the influence of experimental and equipment operating condition was very small. Reliable and accurate determination of the concentrations of intracellular metabolites in Pichia pastoris was obtained. The works lays the foundation for comprehensive regulation mechanism research and efficient recombinant protein production in Pichia pastoris.
The yeast Pichia pastoris is an effective host for recombinant protein production and the recombinant protein production level is tightly related to the concentrations of intracellular metabolites. The intracellular metabolites have the features of wide range of types, distinct variation in physical and chemical properties, rapid turning-over and low concentration, so it is difficult to quantify their concentrations precisely. In this experiment, we tried to make it possible by combining ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry and 13C isotope labeling techniques. 64 metabolites including organic acids, sugar phosphate, nucleoside substance, amino acid were successfully separated by UPLC with three kinds of chromatography column. The appropriate and unique ion pairs and collision voltages were found after the mass spectrometry condition optimization. By using the U13C metabolites as internal standards collected from the cells growing on U13C-glucose as sole carbon source, the standard curves of 53 metabolites were established. The results showed that the method presented here had a high accuracy. The correlation coefficients were above 0.99. The method also had a good reproducibility, and the influence of experimental and equipment operating condition was very small. Reliable and accurate determination of the concentrations of intracellular metabolites in Pichia pastoris was obtained. The works lays the foundation for comprehensive regulation mechanism research and efficient recombinant protein production in Pichia pastoris.
2016, 44(2): 241-246
doi: 10.11895/j.issn.0253-3820.150666
Abstract:
An online comprehensive two-dimensional liquid-gas chromatography method was developed to determine the benzo[a]pyrene (B[a]P) in mainstream cigarette smoke. The B[a]P in mainstream cigarette smoke was collected by a cambridge filter pad, then the pad was extracted with cyclohexane and the extract was quantitatively analyzed by online LC-GC/MS with B[a]P-D12 as an internal standard. After direct injection into the performance liquid chromatography, the benzo[a]pyrene in the samples were separated by micro silica gel column and cut into the gas chromatography. After draining the solvent, the benzo[a]pyrene was separated by capillary column gas chromatography warming and detected by mass spectrometry detection. By using silica gel column chromatography and gas chromatography-mass spectrometry in combination, the benzo[a]pyrene in the mainstream cigarette smoke was directly detected without any sample pretreatment. The sample injection volume of the method could reach 40 μL each time, which was far greater than that of conventional gas chromatography-mass spectrometry (2.0 μL of sample injection volume), resulting in an increasing analysis sensitivity of 20 times. The linearity range of the method (R2=0.999) was in the range of 0.08 ng/L to 50 ng/L. The recoveries at three spiked levels ranged from 94.2% to 105.5% and the limit of detection was 0.09 ng/cig. This method was applied for the determination of benzo[a]pyrene in 14 kind cigarettes in Chinese marked and the reference cigarettes 2R4F, and the determination results were consistent with GB/T21130-2007 method.
An online comprehensive two-dimensional liquid-gas chromatography method was developed to determine the benzo[a]pyrene (B[a]P) in mainstream cigarette smoke. The B[a]P in mainstream cigarette smoke was collected by a cambridge filter pad, then the pad was extracted with cyclohexane and the extract was quantitatively analyzed by online LC-GC/MS with B[a]P-D12 as an internal standard. After direct injection into the performance liquid chromatography, the benzo[a]pyrene in the samples were separated by micro silica gel column and cut into the gas chromatography. After draining the solvent, the benzo[a]pyrene was separated by capillary column gas chromatography warming and detected by mass spectrometry detection. By using silica gel column chromatography and gas chromatography-mass spectrometry in combination, the benzo[a]pyrene in the mainstream cigarette smoke was directly detected without any sample pretreatment. The sample injection volume of the method could reach 40 μL each time, which was far greater than that of conventional gas chromatography-mass spectrometry (2.0 μL of sample injection volume), resulting in an increasing analysis sensitivity of 20 times. The linearity range of the method (R2=0.999) was in the range of 0.08 ng/L to 50 ng/L. The recoveries at three spiked levels ranged from 94.2% to 105.5% and the limit of detection was 0.09 ng/cig. This method was applied for the determination of benzo[a]pyrene in 14 kind cigarettes in Chinese marked and the reference cigarettes 2R4F, and the determination results were consistent with GB/T21130-2007 method.
2016, 44(2): 247-251
doi: 10.11895/j.issn.0253-3820.150655
Abstract:
A bionic method, in vitro digestion, was used for the pretreatment of oyster and clam samples. The oyster and clam samples were digested at 37℃ under the action of bionic digestive juice including saliva, gastric juice and intestinal juice. The contents of trace metals in in vitro digestion extracts (gastric juice extracts and intestinal juice extracts) were determined by atomic absorption spectrometry. The bioaccessibility of trace metals was assessed using the contents of trace metals in bionic extracts. The results showed that the contents of Fe, Cu, Zn and Cd in gastric juice extracts of in vitro digestion on oysters were higher than those in intestinal juice extracts. The contents of Fe and Cu in gastric juice extracts of in vitro digestion on clam were not obviously different with that of in intestinal juice extracts. Otherwise, the contents of Zn and Cd in gastric juice extracts were much higher than those of in intestinal juice extracts. The bioaccessibility of Fe, Cu, Zn and Cd in oysters using in vitro digestion was 60.2%, 83.6%, 83.1% and 76.8%, respectively. The bioaccessibility of Fe, Cu, Zn and Cd in clams was 46.3%, 86.3%, 85.3% and 87.7%, respectively. The results will provide a scientific basis for further researches such as bioaccumulation and bioavailability of trace metal in oysters and clams, evaluation of the health risk of Cd from oyster and clam consumption.
A bionic method, in vitro digestion, was used for the pretreatment of oyster and clam samples. The oyster and clam samples were digested at 37℃ under the action of bionic digestive juice including saliva, gastric juice and intestinal juice. The contents of trace metals in in vitro digestion extracts (gastric juice extracts and intestinal juice extracts) were determined by atomic absorption spectrometry. The bioaccessibility of trace metals was assessed using the contents of trace metals in bionic extracts. The results showed that the contents of Fe, Cu, Zn and Cd in gastric juice extracts of in vitro digestion on oysters were higher than those in intestinal juice extracts. The contents of Fe and Cu in gastric juice extracts of in vitro digestion on clam were not obviously different with that of in intestinal juice extracts. Otherwise, the contents of Zn and Cd in gastric juice extracts were much higher than those of in intestinal juice extracts. The bioaccessibility of Fe, Cu, Zn and Cd in oysters using in vitro digestion was 60.2%, 83.6%, 83.1% and 76.8%, respectively. The bioaccessibility of Fe, Cu, Zn and Cd in clams was 46.3%, 86.3%, 85.3% and 87.7%, respectively. The results will provide a scientific basis for further researches such as bioaccumulation and bioavailability of trace metal in oysters and clams, evaluation of the health risk of Cd from oyster and clam consumption.
2016, 44(2): 252-257
doi: 10.11895/j.issn.0253-3820.150784
Abstract:
Dielectric barrier discharge ion source is an ambient ion source. Coupled with its advantages of solvent-free method, extensive application scope and easy miniaturization, it has attracted widespread attention. The conventional dielectric barrier discharge ion source uses surface double electrode or needle-ring electrode designs. The grounded electrode of the former can weaken ionization head energy formed in strong electric field of helium ionization, and shorten the distance of plasma beam. The electric field of the latter mainly concentrates on the peak of the needle electrode, which can weaken the energy of ionization head and make the length of the plasma beam shorter than the surface double electrode. In this work, the influencing factors of discharge were analyzed, and the electric field was adjusted by changing the shape of the electrode and increasing insulation medium components, thus forcing the strong electric field to focus on one side of the electrode, which could avoid the reflux discharge phenomenon and achieve stable and efficient plasma beam. The maximum length of plasma beam could reach more than 8 cm. On the basis, a single electrode dielectric barrier discharge ion source (DBDI), mainly composed of inert carrier gas, high voltage electrode, insulation tube, gas control and temperature control parts, was developed. Using the new type of ion source, the liquid sample of caffeine and the solid tablets of acetaminophen were analyzed by DBDI-MS. The correlation coefficient of the caffeine quantitative curve was 99.66%, and the signal to noise ratio of 100 μg/L was 23. The main component of the acetaminophen was C8H9NO2 that could be rapidly detected in the mass spectrum, and the response intensity was 1.26×106. The results showed that the new type of ion source could realize the quantitative and rapid in situ analysis of the sample.
Dielectric barrier discharge ion source is an ambient ion source. Coupled with its advantages of solvent-free method, extensive application scope and easy miniaturization, it has attracted widespread attention. The conventional dielectric barrier discharge ion source uses surface double electrode or needle-ring electrode designs. The grounded electrode of the former can weaken ionization head energy formed in strong electric field of helium ionization, and shorten the distance of plasma beam. The electric field of the latter mainly concentrates on the peak of the needle electrode, which can weaken the energy of ionization head and make the length of the plasma beam shorter than the surface double electrode. In this work, the influencing factors of discharge were analyzed, and the electric field was adjusted by changing the shape of the electrode and increasing insulation medium components, thus forcing the strong electric field to focus on one side of the electrode, which could avoid the reflux discharge phenomenon and achieve stable and efficient plasma beam. The maximum length of plasma beam could reach more than 8 cm. On the basis, a single electrode dielectric barrier discharge ion source (DBDI), mainly composed of inert carrier gas, high voltage electrode, insulation tube, gas control and temperature control parts, was developed. Using the new type of ion source, the liquid sample of caffeine and the solid tablets of acetaminophen were analyzed by DBDI-MS. The correlation coefficient of the caffeine quantitative curve was 99.66%, and the signal to noise ratio of 100 μg/L was 23. The main component of the acetaminophen was C8H9NO2 that could be rapidly detected in the mass spectrum, and the response intensity was 1.26×106. The results showed that the new type of ion source could realize the quantitative and rapid in situ analysis of the sample.
2016, 44(2): 258-264
doi: 10.11895/j.issn.0253-3820.150391
Abstract:
Polyaniline/chitosan composite membrane was modified on the surface of a screen printed carbon electrode by cyclic voltammetry (CV), and then anti-uniconazole antibodies were immobilized on the electrode based on electrostatic attraction. The impedance immunosensor for the determination of uniconazole was thus constructed. CV and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical properties of immunosensor. Several factors affecting the immunoreaction were investigated, including the pH of phosphate buffer saline (PBS), incubation temperature and time. The performance of the proposed immunosensor was investigated under the optimized conditions. The immunosensor exhibited advantages of high accuracy, high sensitivity and specificity, good reproducibility and stability. The immunosensor could detect uniconazole in a linear range of 0.01-100 mg/L (R=0.998), and the detection limit was 8 μg/L (3σ). The average recoveries were 98.5%-104.6% and the relative standard deviations were 3.3-4.3% at the spiked level of 0.05, 0.10 and 1.0 mg/kg in cabbage, and the detection results were consistent with the results obtained by gas chromatography.
Polyaniline/chitosan composite membrane was modified on the surface of a screen printed carbon electrode by cyclic voltammetry (CV), and then anti-uniconazole antibodies were immobilized on the electrode based on electrostatic attraction. The impedance immunosensor for the determination of uniconazole was thus constructed. CV and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical properties of immunosensor. Several factors affecting the immunoreaction were investigated, including the pH of phosphate buffer saline (PBS), incubation temperature and time. The performance of the proposed immunosensor was investigated under the optimized conditions. The immunosensor exhibited advantages of high accuracy, high sensitivity and specificity, good reproducibility and stability. The immunosensor could detect uniconazole in a linear range of 0.01-100 mg/L (R=0.998), and the detection limit was 8 μg/L (3σ). The average recoveries were 98.5%-104.6% and the relative standard deviations were 3.3-4.3% at the spiked level of 0.05, 0.10 and 1.0 mg/kg in cabbage, and the detection results were consistent with the results obtained by gas chromatography.
2016, 44(2): 265-272
doi: 10.11895/j.issn.0253-3820.150119
Abstract:
A reliable, efficient and simple method was developed for releasing, enrichment and purification of N-glycan from glycoprotein based on electrospray ionization mass spectrometric (ESI-MS) detection technology. The bovine ribonuclease B(Rib B) and ovalbumin were used as model glycoprotein samples and subjected to direct enzymolysis to investigate the purification effects of four different purification methods. Then the enzymatic efficiency of micro-scale complex fetal bovine serum sample subjected to direct and indirect enzymolysis after polyvinylidene fluoride (PVDF) membrane enrichment was fully investigated. Finally, a pretreatment method of N-linked glycans from glycoprotein in micro-scale complex biological sample analyzed by ESI-MS was established. The PNGase F was exploited for directly releasing of glycans from glycoprotein enriched on PVDF membrane (37℃, 24 h). Then microcrystalline cellulose chromatography column combined with graphite carbon chromatography column was used to enrich and purify glycans from enzymolysis products. The assay was eventually applied to pretreatment of N-glycan in micro-scale biological samples (μg level) of fetal bovine serum and healthy human serum for MS analysis. The method with universality showed good prospects in pretreatment of N-glycan in micro-scale biological sample for MS analysis.
A reliable, efficient and simple method was developed for releasing, enrichment and purification of N-glycan from glycoprotein based on electrospray ionization mass spectrometric (ESI-MS) detection technology. The bovine ribonuclease B(Rib B) and ovalbumin were used as model glycoprotein samples and subjected to direct enzymolysis to investigate the purification effects of four different purification methods. Then the enzymatic efficiency of micro-scale complex fetal bovine serum sample subjected to direct and indirect enzymolysis after polyvinylidene fluoride (PVDF) membrane enrichment was fully investigated. Finally, a pretreatment method of N-linked glycans from glycoprotein in micro-scale complex biological sample analyzed by ESI-MS was established. The PNGase F was exploited for directly releasing of glycans from glycoprotein enriched on PVDF membrane (37℃, 24 h). Then microcrystalline cellulose chromatography column combined with graphite carbon chromatography column was used to enrich and purify glycans from enzymolysis products. The assay was eventually applied to pretreatment of N-glycan in micro-scale biological samples (μg level) of fetal bovine serum and healthy human serum for MS analysis. The method with universality showed good prospects in pretreatment of N-glycan in micro-scale biological sample for MS analysis.
2016, 44(2): 273-280
doi: 10.11895/j.issn.0253-3820.150735
Abstract:
A robust method for measuring sulfur content in sediments was established using double focusing inductively coupled plasma mass spectrometry at medium resolution combined with microwave digestion technique. The capability of standard curve method (SCM) and standard addition method (SAM) using Rh as internal standard was compared in correction of the matrix effect. The results showed the matrix effect was not suppressed by SCM, but was effectively eliminated by SAM with drawback of low sample throughout. Therefore, the standard addition calibration method (SACM) was creatively proposed in this study, which can simply and easily correct the matrix effect as the matrix content of sample and standard solution was matched within ±50%. The detection limit and liner range of this method were proved to be 0.5 mg/kg and 3.0-1000 μg/L, respectively, with the spiked recovery of 95.8%-99.2%. Four sediment standard reference materials GBW07306, GBW07309, GBW07313 and SRM1646a were analyzed repetitively with the obtained sulfur contents of (853±14) μg/g (2σ, n=12), (181±7) μg/g (2σ, n=9), (3131±52) μg/g (2σ, n=12) and (3543±70) μg/g (2σ, n=9), respectively. The relative error of the four reference materials was +8.8%, +13.3%, +1.0% and +0.7%, respectively, with precision (RSD) less than 2%. This method was applied to determine the sulfur content in the sediment cores collected in the Yangtze Estuary and Hangzhou Bay. This proposed method was demonstrated as an accurate and rapid way of determining sulfur content in great batch of sediments samples, and has a broad application range including soil samples.
A robust method for measuring sulfur content in sediments was established using double focusing inductively coupled plasma mass spectrometry at medium resolution combined with microwave digestion technique. The capability of standard curve method (SCM) and standard addition method (SAM) using Rh as internal standard was compared in correction of the matrix effect. The results showed the matrix effect was not suppressed by SCM, but was effectively eliminated by SAM with drawback of low sample throughout. Therefore, the standard addition calibration method (SACM) was creatively proposed in this study, which can simply and easily correct the matrix effect as the matrix content of sample and standard solution was matched within ±50%. The detection limit and liner range of this method were proved to be 0.5 mg/kg and 3.0-1000 μg/L, respectively, with the spiked recovery of 95.8%-99.2%. Four sediment standard reference materials GBW07306, GBW07309, GBW07313 and SRM1646a were analyzed repetitively with the obtained sulfur contents of (853±14) μg/g (2σ, n=12), (181±7) μg/g (2σ, n=9), (3131±52) μg/g (2σ, n=12) and (3543±70) μg/g (2σ, n=9), respectively. The relative error of the four reference materials was +8.8%, +13.3%, +1.0% and +0.7%, respectively, with precision (RSD) less than 2%. This method was applied to determine the sulfur content in the sediment cores collected in the Yangtze Estuary and Hangzhou Bay. This proposed method was demonstrated as an accurate and rapid way of determining sulfur content in great batch of sediments samples, and has a broad application range including soil samples.
2016, 44(2): 281-288
doi: 10.11895/j.issn.0253-3820.150558
Abstract:
A fast analytical method was developed for the determination of main composition of fatty acid monoglycerides, including monopalmitin, monostearin, monoolein and monolinolein, in monoglycerede emulsifiers by ultra-performance convergence chromatography-mass spectrometry. Their contents were compared in the 3 emulsifiers from different sources. The sample was directly dissolved with n-hexane/isopropanol (7:3, /V) The chromatographic separation was performed on the ACQUITY UPC2 BEH 2-EP column (2.1 mm×100 mm, 1.7 μm) using the mobile phases of carbon dioxide and methanol/acetonitrile (1:1, V/V) solution with gradient elution. The separated compounds were detected by MS detector in positive electrospray ionization (ESI+) and quantified by external standard method. The results showed that the calibration curves of monopalmitin,monostearin,monoolein and monolinolein were linear in the range of 0.20-50 mg/L, 0.20-50 mg/L, 0.25-62.5 mg/L and 0.20-50 mg/L, respectively, with correlation coefficients not less than 0.9983. The limits of quantification (S/N≥10) of the four fatty acid monoglycerides were 0.018-0.046 mg/L. The average recoveries for the four monoglycerides at three spiked levels were 88.0%-110.5% with relative standard deviations of 1.1%-4.1%. The proposed method showed high performance, good selectivity and fast analysis for the underivatized monoglyceride samples. It would provide a new chromatographic technology for the content analysis of monoglycerides in the emulsifier.
A fast analytical method was developed for the determination of main composition of fatty acid monoglycerides, including monopalmitin, monostearin, monoolein and monolinolein, in monoglycerede emulsifiers by ultra-performance convergence chromatography-mass spectrometry. Their contents were compared in the 3 emulsifiers from different sources. The sample was directly dissolved with n-hexane/isopropanol (7:3, /V) The chromatographic separation was performed on the ACQUITY UPC2 BEH 2-EP column (2.1 mm×100 mm, 1.7 μm) using the mobile phases of carbon dioxide and methanol/acetonitrile (1:1, V/V) solution with gradient elution. The separated compounds were detected by MS detector in positive electrospray ionization (ESI+) and quantified by external standard method. The results showed that the calibration curves of monopalmitin,monostearin,monoolein and monolinolein were linear in the range of 0.20-50 mg/L, 0.20-50 mg/L, 0.25-62.5 mg/L and 0.20-50 mg/L, respectively, with correlation coefficients not less than 0.9983. The limits of quantification (S/N≥10) of the four fatty acid monoglycerides were 0.018-0.046 mg/L. The average recoveries for the four monoglycerides at three spiked levels were 88.0%-110.5% with relative standard deviations of 1.1%-4.1%. The proposed method showed high performance, good selectivity and fast analysis for the underivatized monoglyceride samples. It would provide a new chromatographic technology for the content analysis of monoglycerides in the emulsifier.
2016, 44(2): 289-296
doi: 10.11895/j.issn.0253-3820.150830
Abstract:
A high-throughput method was established for the simultaneous determination of 27 kinds of β-agonists, 3 kinds of β-blockers and 2 kinds of glycopeptide antibiotics in animal meat by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample underwent enzymolysis and the protein precipitation treatment was extracted with a mixture of ethyl acetate-isopropanol (6:4, V/V), and cleaned up at a Strata-X-C solid phase extraction cartridge. The 32 targets were separated on a Waters BEH C18 column by gradient elution with acetonitrile-0.1% formaic acid as mobile phase, ionized with positive electrospray ionization (ESI+), detected under multiple reaction monitoring mode, and quantified with external standard method. The results showed that the target compounds displayed excellent linearity in the concentration of 5-500 μg/L with correlation coefficients larger than 0.995. The limits of detection were 5 μg/kg for dopamine, reproterol, vancomycin and norvancomycin, and were 3 μg/kg for the others. The average recoveries were in the range of 83.6%-103.0% at two spiked levels. The intra-day RSDs were ranged from 3.9% to 10.4%, and the inter-day RSDs were no more than 9.8%. The developed method was accurate and sensitive, and was suitable for the high-throughput quantitative and qualitative analysis of β-agonists, β-blockers and glycopeptide antibiotics in animal meat.
A high-throughput method was established for the simultaneous determination of 27 kinds of β-agonists, 3 kinds of β-blockers and 2 kinds of glycopeptide antibiotics in animal meat by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample underwent enzymolysis and the protein precipitation treatment was extracted with a mixture of ethyl acetate-isopropanol (6:4, V/V), and cleaned up at a Strata-X-C solid phase extraction cartridge. The 32 targets were separated on a Waters BEH C18 column by gradient elution with acetonitrile-0.1% formaic acid as mobile phase, ionized with positive electrospray ionization (ESI+), detected under multiple reaction monitoring mode, and quantified with external standard method. The results showed that the target compounds displayed excellent linearity in the concentration of 5-500 μg/L with correlation coefficients larger than 0.995. The limits of detection were 5 μg/kg for dopamine, reproterol, vancomycin and norvancomycin, and were 3 μg/kg for the others. The average recoveries were in the range of 83.6%-103.0% at two spiked levels. The intra-day RSDs were ranged from 3.9% to 10.4%, and the inter-day RSDs were no more than 9.8%. The developed method was accurate and sensitive, and was suitable for the high-throughput quantitative and qualitative analysis of β-agonists, β-blockers and glycopeptide antibiotics in animal meat.
2016, 44(2): 297-304
doi: 10.11895/j.issn.0253-3820.150648
Abstract:
A solid phase extraction (SPE)-gas chromatography coupled with electron capture detection (GC-ECD) method was developed for the simultaneous determination of 16 nitrobenzene compounds in drinking water. The chromatographic conditions, i.e. the chromatographic column and the programmed temperature, were optimized, and the extraction conditions, i.e. the type of extraction column, elution solvent and volume of elution solvent, were also optimized. Water samples were extracted with Oasis HLB columns and eluted by the mixture of n-hexane and acetone (3:1, V/V). All the target compounds were chromatographically separated on a DB-1701 capillary column with programed temperature, and were detected by electron capture detector. The favorable resolutions of all target compounds were achieved within 33 min. Under the optimal analytical conditions, the peak area of each analyte and its concentration had a good correlation within the linear range (r≥0.998). The limit of detection (LOD) and limit of quantification (LOQ) of the method were 0.01-0.77 μg/L (S/N=3) and 0.03-2.57 μg/L (S/N=10), respectively. The intra- and inter-day relative standard deviations (RSDs) of the sample were 1.0%-3.8% and 2.3%-4.8%, respectively. Spiked recoveries of the analytes were 83.6%-111.8% and the RSDs of the spiked samples were 1.2%-5.1%. This proposed method has been applied in the detection of 50 water samples. The results indicated that the new solid phase extraction-gas chromatography coupled with electron capture detection method was specific, sensitive and reproducible, and could be used for the determination of 16 nitrobenzene compounds in drinking water.
A solid phase extraction (SPE)-gas chromatography coupled with electron capture detection (GC-ECD) method was developed for the simultaneous determination of 16 nitrobenzene compounds in drinking water. The chromatographic conditions, i.e. the chromatographic column and the programmed temperature, were optimized, and the extraction conditions, i.e. the type of extraction column, elution solvent and volume of elution solvent, were also optimized. Water samples were extracted with Oasis HLB columns and eluted by the mixture of n-hexane and acetone (3:1, V/V). All the target compounds were chromatographically separated on a DB-1701 capillary column with programed temperature, and were detected by electron capture detector. The favorable resolutions of all target compounds were achieved within 33 min. Under the optimal analytical conditions, the peak area of each analyte and its concentration had a good correlation within the linear range (r≥0.998). The limit of detection (LOD) and limit of quantification (LOQ) of the method were 0.01-0.77 μg/L (S/N=3) and 0.03-2.57 μg/L (S/N=10), respectively. The intra- and inter-day relative standard deviations (RSDs) of the sample were 1.0%-3.8% and 2.3%-4.8%, respectively. Spiked recoveries of the analytes were 83.6%-111.8% and the RSDs of the spiked samples were 1.2%-5.1%. This proposed method has been applied in the detection of 50 water samples. The results indicated that the new solid phase extraction-gas chromatography coupled with electron capture detection method was specific, sensitive and reproducible, and could be used for the determination of 16 nitrobenzene compounds in drinking water.
2016, 44(2): 305-309
doi: 10.11895/j.issn.0253-3820.150793
Abstract:
Outlier detection is an important task in multivariate calibration because the quality of a calibration model is determined by that of the calibration data. An outlier detection method is proposed for near infrared (NIR) spectral analysis. The method is based on the definition of outlier and the principle of partial least squares (PLS) regression, i.e., an outlier in a dataset behaves differently from the rest, and the prediction result of a PLS model is an accumulation of several independent latent variables. Therefore, the proposed method builds a PLS model with a calibration dataset, and then the contribution of each latent variable is investigated. Outliers can be detected by comparing these contributions. An NIR spectral dataset of orange juice samples is adopted for testing the method. Six outliers are detected in the calibration set. The root mean squared error of cross validation (RMSECV) becomes to 4.809 from 16.870 and the root mean squared error of prediction (RMSEP) becomes to 3.332 from 3.688 after the removal of the outliers. Compared with a robust regression method, the result of the proposed method seems more reasonable.
Outlier detection is an important task in multivariate calibration because the quality of a calibration model is determined by that of the calibration data. An outlier detection method is proposed for near infrared (NIR) spectral analysis. The method is based on the definition of outlier and the principle of partial least squares (PLS) regression, i.e., an outlier in a dataset behaves differently from the rest, and the prediction result of a PLS model is an accumulation of several independent latent variables. Therefore, the proposed method builds a PLS model with a calibration dataset, and then the contribution of each latent variable is investigated. Outliers can be detected by comparing these contributions. An NIR spectral dataset of orange juice samples is adopted for testing the method. Six outliers are detected in the calibration set. The root mean squared error of cross validation (RMSECV) becomes to 4.809 from 16.870 and the root mean squared error of prediction (RMSEP) becomes to 3.332 from 3.688 after the removal of the outliers. Compared with a robust regression method, the result of the proposed method seems more reasonable.
2016, 44(2): 310-314
doi: 10.11895/j.issn.0253-3820.150534
Abstract:
By using fluorophore (FAM) labeled aptamers as recognition elements and graphene oxide as a quencher, a highly selective and sensitive sensor was constructed for the fast and accurate detection of insulin. After the aptamer binding with graphene oxide, fluorescence will be quenched and fluorescence intensity disappeared; after addition of insulin, the solution fluorescence was restored. Based on the fact, we established a method for the determination of insulin concentration by measuring the fluorescence intensity. The results showed that the concentration of insulin in the range of 5×10-8-1×10-5 mol/L had a good linear relationship with the fluorescence intensity. The detection limit was 10 nmol/L. This method of detecting insulin had obvious advantages of fast detection speed, high selectivity and low detection limit.
By using fluorophore (FAM) labeled aptamers as recognition elements and graphene oxide as a quencher, a highly selective and sensitive sensor was constructed for the fast and accurate detection of insulin. After the aptamer binding with graphene oxide, fluorescence will be quenched and fluorescence intensity disappeared; after addition of insulin, the solution fluorescence was restored. Based on the fact, we established a method for the determination of insulin concentration by measuring the fluorescence intensity. The results showed that the concentration of insulin in the range of 5×10-8-1×10-5 mol/L had a good linear relationship with the fluorescence intensity. The detection limit was 10 nmol/L. This method of detecting insulin had obvious advantages of fast detection speed, high selectivity and low detection limit.
2016, 44(2): 315-318
doi: 10.11895/j.issn.0253-3820.150623
Abstract:
Cadmium telluride quantum dots (CdTe QDs) as a novel inorganic matrix were applied in matrix assisted laser desorption ionization time-of-flight mass spectrometric (MALDI-TOF-MS) analysis of perfluorinated compounds including perfluorooctane sulfonate (PFOS), perfluorodecane sulfonate (PFDS), perfluorohexane sulfonate (PFHxS) and perfluoroheptane sulfonate (PFHpS), and its performance was investigated and compared with conventional organic matrix involving α-cyano-4-hydroxycinnamic acid (CHCA) and 1,8-bis(dimethylamino)naphthalene (DMAN) under the same mass spectrometric conditions. In the experiment, the analytes and matrix were mixed on the sample plate. The crystal of analyte and matrix was excited by using 337-nm laser after the solvent was evaporated, and was detected under negative ion mode of MALDI-TOF-MS. The results demonstrated that CdTe QDs with high UV absorption could be an efficient inorganic matrix for enhancement of peak intensity in MALDI-TOF-MS analysis of perfluorinated compounds. Additionally, mechanism of ionization process was briefly discussed.
Cadmium telluride quantum dots (CdTe QDs) as a novel inorganic matrix were applied in matrix assisted laser desorption ionization time-of-flight mass spectrometric (MALDI-TOF-MS) analysis of perfluorinated compounds including perfluorooctane sulfonate (PFOS), perfluorodecane sulfonate (PFDS), perfluorohexane sulfonate (PFHxS) and perfluoroheptane sulfonate (PFHpS), and its performance was investigated and compared with conventional organic matrix involving α-cyano-4-hydroxycinnamic acid (CHCA) and 1,8-bis(dimethylamino)naphthalene (DMAN) under the same mass spectrometric conditions. In the experiment, the analytes and matrix were mixed on the sample plate. The crystal of analyte and matrix was excited by using 337-nm laser after the solvent was evaporated, and was detected under negative ion mode of MALDI-TOF-MS. The results demonstrated that CdTe QDs with high UV absorption could be an efficient inorganic matrix for enhancement of peak intensity in MALDI-TOF-MS analysis of perfluorinated compounds. Additionally, mechanism of ionization process was briefly discussed.
2016, 44(2): 319-326
doi: 10.11895/j.issn.0253-3820.150746
Abstract:
Counter-current chromatography (CCC) is a quick preparative separation technique based on the different partition coefficient in liquid-liquid solvent systems. This paper reviews recent research progress in the region of solvent systems, instruments improvement of CCC. Moreover, some application prospects about enantioseparation of racemic compounds by CCC are also discussed. Finally, the contents and goal of further research in this field is discussed.
Counter-current chromatography (CCC) is a quick preparative separation technique based on the different partition coefficient in liquid-liquid solvent systems. This paper reviews recent research progress in the region of solvent systems, instruments improvement of CCC. Moreover, some application prospects about enantioseparation of racemic compounds by CCC are also discussed. Finally, the contents and goal of further research in this field is discussed.
