An efficient method using multiwalled carbon nanotubes(MWCNTs)as dispersive solid-phase extraction sorbent was established for determining chlorantraniliprole residues in fresh tea leaves,which are known to be a troub...An efficient method using multiwalled carbon nanotubes(MWCNTs)as dispersive solid-phase extraction sorbent was established for determining chlorantraniliprole residues in fresh tea leaves,which are known to be a troublesome matrix containing abundant pigments,via gas chromatography with an electron capture detector.Acetonitrile was used as the extraction solvent,with sodium chloride enhancing the analyte partition in the organic phase.The optimal mixture of MWCNTs and primary secondary amine(PSA)was based on the distribution of the target analyte recovery and on the clean-up efficiency;while matrix-matched calibration was recommended to combat the matrix effect.Mean recoveries of 95.2%–108.8%were obtained with intraday and interday precisions of less than 7.9%and 10.3%,respectively.Good linearity was observed for concentrations of 0.02–1.0 mg/kg with a correlation coefficient of 0.9984.The limits of detection and quantification were 0.005 mg/kg and 0.02 mg/kg,respectively.The method was employed to investigate the dissipation dynamics of chlorantraniliprole in fresh tea leaves with real field samples.Consequently,the dissipation rates of chlorantraniliprole in fresh tea leaves followed pseudo-first-order kinetics with a half-life of 1.9 d,and the average chlorantraniliprole residue content was below 0.02 mg/kg with a harvest withholding period of 14 d.展开更多
A rapid and accurate quantitative method of high performance liquid chromatography( HPLC) with fluorescence detector has been developed for the analysis of 18 kinds of amino acids in fresh tea leaves. The samples were...A rapid and accurate quantitative method of high performance liquid chromatography( HPLC) with fluorescence detector has been developed for the analysis of 18 kinds of amino acids in fresh tea leaves. The samples were minced and mixed,and extracted with ultra pure water at 90℃ for 20 min. The 6-aminoquinolyl N-hydroxy-succinimidyl carbamate( AQC) was used as pre-column derivatization reagent. Gradient HPLC separation was performed on a C_(18) column( Symmetry C_(18),3. 9 mm × 15 cm,4 μm). Good linearity between concentrations and peak areas was achieved in the concentration range of 5. 0-250 μmol/L for 18 kinds of amino acids. The method was validated by the analysis of five replicates. The 18 kinds of amino acid standards were spiked in fresh tea leaf samples and the average recovery rate was 86. 25%-109. 05% with relative standard deviations( n = 5) ranging from 6. 03% to 10. 56%. The limit of detection( LOD) for the analytes was0. 05-1. 27 μmol/L. The method was successfully applied to the analysis of the 18 kinds of amino acids in fresh tea leaves from east Dongting and west Dongting mountains in Suzhou. The results indicate that the method is simple,rapid,precise and reliable.展开更多
Tis paper attempts to establish a psychophysical basis for both stationary(tension in chord sonorities)and transitional(resolution in chord progressions)harmony.Harmony studies the phenomenon of combining notes in mus...Tis paper attempts to establish a psychophysical basis for both stationary(tension in chord sonorities)and transitional(resolution in chord progressions)harmony.Harmony studies the phenomenon of combining notes in music to produce a pleasing efect greater than the sum of its parts.Being both aesthetic and mathematical in nature,it has bafed some of the brightest minds in physics and mathematics for centuries.With stationary harmony acoustics,traditional theories explaining consonances and dissonances that have been widely accepted are centred around two schools:rational relationships(commonly credited to Pythagoras)and Helmholtz’s beating frequencies.Te frst is more of an attribution than a psychoacoustic explanation while electrophysiological(amongst other)discrepancies with the second still remain disputed.Transitional harmony,on the other hand,is a more complex problem that has remained largely elusive to acoustic science even today.In order to address both stationary and transitional harmony,we frst propose the notion of interharmonic and subharmonic modulations to address the summation of adjacent and distant sinusoids in a chord.Based on this,earlier parts of this paper then bridges the two schools and shows how they stem from a single equation.Later parts of the paper focuses on subharmonic modulations to explain aspects of harmony that interharmonic modulations cannot.Introducing the concept of stationary and transitional subharmonic tensions,we show how it can explain perceptual concepts such as tension in stationary harmony and resolution in transitional harmony,by which we also address the fve fundamental questions of psychoacoustic harmony such as why the pleasing efect of harmony is greater than that of the sum of its parts.Finally,strong correlations with traditional music theory and perception statistics afrm our theory with stationary and transitional harmony.展开更多
基金Science and Technology Project of Suzhou(Grant Nos.:SNG201622 and SNG201644)。
文摘An efficient method using multiwalled carbon nanotubes(MWCNTs)as dispersive solid-phase extraction sorbent was established for determining chlorantraniliprole residues in fresh tea leaves,which are known to be a troublesome matrix containing abundant pigments,via gas chromatography with an electron capture detector.Acetonitrile was used as the extraction solvent,with sodium chloride enhancing the analyte partition in the organic phase.The optimal mixture of MWCNTs and primary secondary amine(PSA)was based on the distribution of the target analyte recovery and on the clean-up efficiency;while matrix-matched calibration was recommended to combat the matrix effect.Mean recoveries of 95.2%–108.8%were obtained with intraday and interday precisions of less than 7.9%and 10.3%,respectively.Good linearity was observed for concentrations of 0.02–1.0 mg/kg with a correlation coefficient of 0.9984.The limits of detection and quantification were 0.005 mg/kg and 0.02 mg/kg,respectively.The method was employed to investigate the dissipation dynamics of chlorantraniliprole in fresh tea leaves with real field samples.Consequently,the dissipation rates of chlorantraniliprole in fresh tea leaves followed pseudo-first-order kinetics with a half-life of 1.9 d,and the average chlorantraniliprole residue content was below 0.02 mg/kg with a harvest withholding period of 14 d.
基金Supported by Open Project of the Key Laboratory of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base(201603)Basic Research Project of Application of Suzhou City(SNG201622)
文摘A rapid and accurate quantitative method of high performance liquid chromatography( HPLC) with fluorescence detector has been developed for the analysis of 18 kinds of amino acids in fresh tea leaves. The samples were minced and mixed,and extracted with ultra pure water at 90℃ for 20 min. The 6-aminoquinolyl N-hydroxy-succinimidyl carbamate( AQC) was used as pre-column derivatization reagent. Gradient HPLC separation was performed on a C_(18) column( Symmetry C_(18),3. 9 mm × 15 cm,4 μm). Good linearity between concentrations and peak areas was achieved in the concentration range of 5. 0-250 μmol/L for 18 kinds of amino acids. The method was validated by the analysis of five replicates. The 18 kinds of amino acid standards were spiked in fresh tea leaf samples and the average recovery rate was 86. 25%-109. 05% with relative standard deviations( n = 5) ranging from 6. 03% to 10. 56%. The limit of detection( LOD) for the analytes was0. 05-1. 27 μmol/L. The method was successfully applied to the analysis of the 18 kinds of amino acids in fresh tea leaves from east Dongting and west Dongting mountains in Suzhou. The results indicate that the method is simple,rapid,precise and reliable.
文摘Tis paper attempts to establish a psychophysical basis for both stationary(tension in chord sonorities)and transitional(resolution in chord progressions)harmony.Harmony studies the phenomenon of combining notes in music to produce a pleasing efect greater than the sum of its parts.Being both aesthetic and mathematical in nature,it has bafed some of the brightest minds in physics and mathematics for centuries.With stationary harmony acoustics,traditional theories explaining consonances and dissonances that have been widely accepted are centred around two schools:rational relationships(commonly credited to Pythagoras)and Helmholtz’s beating frequencies.Te frst is more of an attribution than a psychoacoustic explanation while electrophysiological(amongst other)discrepancies with the second still remain disputed.Transitional harmony,on the other hand,is a more complex problem that has remained largely elusive to acoustic science even today.In order to address both stationary and transitional harmony,we frst propose the notion of interharmonic and subharmonic modulations to address the summation of adjacent and distant sinusoids in a chord.Based on this,earlier parts of this paper then bridges the two schools and shows how they stem from a single equation.Later parts of the paper focuses on subharmonic modulations to explain aspects of harmony that interharmonic modulations cannot.Introducing the concept of stationary and transitional subharmonic tensions,we show how it can explain perceptual concepts such as tension in stationary harmony and resolution in transitional harmony,by which we also address the fve fundamental questions of psychoacoustic harmony such as why the pleasing efect of harmony is greater than that of the sum of its parts.Finally,strong correlations with traditional music theory and perception statistics afrm our theory with stationary and transitional harmony.
