The dibutyl phthalate （DBP） concentration in liqueur was measured by gas chromatography-mass spectrometry （GC-MS）, and the uncertainty during the mea-surement was evaluated in this study. The results showed that t...The dibutyl phthalate （DBP） concentration in liqueur was measured by gas chromatography-mass spectrometry （GC-MS）, and the uncertainty during the mea-surement was evaluated in this study. The results showed that the combined stan-dard uncertainty was determined as 0.028 and the expanded uncertainty was 0.056 at confidence probability p=95%, coverage factor k=2, by fol owing the methods de-scribed in GB/T 21911-2008 ＂Determination of Phthalate Esters in Foods＂. The av-erage DBP concentration in the liqueur of eight repeated measurements was（0.985＆#177; 0.056） mg/kg finaly.展开更多
Isoproterenol （ISPR） is an important catecholamine‐based drug that is widely used in the treatment of heart disease. However, overdose of this drug is very dangerous to the human body. In this study, a new sensor b...Isoproterenol （ISPR） is an important catecholamine‐based drug that is widely used in the treatment of heart disease. However, overdose of this drug is very dangerous to the human body. In this study, a new sensor based on a pyrogallol red modified‐multiwalled carbon nanotube paste electrode （PGRMMWCNTPE） was prepared and used for high sensitivity determination of ISPR in aqueous solution. Electrocatalytic oxidation of ISPR at the PGRMMWCNTPE was investigated by chronoam‐perometry, cyclic voltammetry, and square‐wave voltammetry. The values of the catalytic rate con‐stant, electron transfer coefficient, and diffusion coefficient for ISPR oxidation were then calculated using voltammetric data. A linear calibration curve was constructed for ISPR concentration in the range 0.8–570μmol/L with a detection limit of 0.47μmol/L ISPR. The sensor was then applied to the determination of ISPR in urine and drug samples with satisfactory results.展开更多
Synthesis and separation of asymmetrically octa-substituted phthalocyanines （Pcs） derivatives obtained by cyclotetramerization of two different phthalonitriles （Pns） precursors is described. The phthalonitriles we...Synthesis and separation of asymmetrically octa-substituted phthalocyanines （Pcs） derivatives obtained by cyclotetramerization of two different phthalonitriles （Pns） precursors is described. The phthalonitriles were designed to have different polarity to enable successful chromatographic isolation. The side-chains was designed to lie perpendicular to the plane of the macrocycle via ketal link. It was hoped that the obtained materials would exhibit enhanced solubility and less columnar aggregation both in solution and in the solid state. The preparation of the ketal compounds （2,2-didodecyl- 1,3-benzodioxoles ） with was performed according to Cole method in which catechol and the didodecyl ketone were refluxed in toluene solution in the presence of a catalytic amount of p-toluene sulphonic acid （PTSA）. The resultant water was removed by azeotropic distillation using a Dean-Stark trap. 2,2-didodecyl-l,3-benzodioxoles was brominated then cyanated as described in literature to give the desired phthalonitrile. The other phthalonitrile （4,5-bis（1＇,4＇,7＇,10＇-tetraoxaundecyl） phthalonitrile was obtained also as described in literature. The structures of the obtained isomers were confirmed by spectroscopic methods. Optical microscopy and differential scanning calorimetry （DSC） measurements revealed that two of the obtained derivatives display hexagonal and rectangular columnar liquid crystalline phases （Dhd＆Drd） over a wide temperature range.展开更多
2-Methyl-4-methoxyaniline （MMA） was synthesized by one-pot method through the hydrogenation and Bamberger rearrangement of o-nitrotoluene in methanol using acidic ionic liquid and 3% Pt/C as catalyst system. The eff...2-Methyl-4-methoxyaniline （MMA） was synthesized by one-pot method through the hydrogenation and Bamberger rearrangement of o-nitrotoluene in methanol using acidic ionic liquid and 3% Pt/C as catalyst system. The effects of ionic liquid type, dosage of ionic liquid and 3% Pt/C, reaction temperature and reaction pressure on o-nitrotoluene conversion and MMA selectivity were investigated. The results indicated that the imidazolium-based acidic ionic liquid which contains SO3H-functionalized cation showed higher selectivity to MMA than other acidic ionic liquids used in this work. Using 1-（propyl-3-sulfonate）-3-methylimidazolium hydrosulfate （[HSO3-pmim][HSO4]） as the acid catalyst, the selectivity to MMA was as high as 67.6% at 97.8% of o-nitrotoluene conversion. As 3% Pt/C increased from 0.01 g to 0.025 g, the selectivity to MMA decreased from 73.4% to 62.5%, because of the hydrogenation of intermediate o-methyl-phenylhydroxylamine to o-toluidine becoming more dominant. An increase in hydrogen pressure also had obviously dramatic effect in lowering the MMA selectivity. After easy separation from the products, the catalyst system could be reused at least 3 times.展开更多
Amino acid neurotransmitters facilitate the transmission of nerve messages across the synapses and play essential roles in the control and regulation of a variety of functions in the central and peripheral nervous sys...Amino acid neurotransmitters facilitate the transmission of nerve messages across the synapses and play essential roles in the control and regulation of a variety of functions in the central and peripheral nervous system. In this study, we developed a sensitive and efficient method using high-performance liquid chromatography （HPLC） with fluorescence detection for the assay of five important amino acid n After derivatization with o-phthaldialdehyde （OPA）, aspartate （Asp）, glutamic acid （Glu）, glycine （Gly）, taurine （Tau） and ）,-aminobutyric acid （GABA） were simultaneously detected in the presence of the internal standard homoserine （Hse）. Precise separation of these five amino acids was achieved using isocratic elution within 24 min. Good linearity was found over the concentration range with correlation coefficients （r2） not less than 0.9998. The limit of detection （LOD） values were no more than 10 nmol/L. The intra- and inter-day reproducibility was adequate with the relative standard deviation （RSD） of 10.5% or below. This method has also been applied to the analysis of amino acids in the substantia nigra and striatum samples obtained from C57BL/6 mice.展开更多
文摘The dibutyl phthalate （DBP） concentration in liqueur was measured by gas chromatography-mass spectrometry （GC-MS）, and the uncertainty during the mea-surement was evaluated in this study. The results showed that the combined stan-dard uncertainty was determined as 0.028 and the expanded uncertainty was 0.056 at confidence probability p=95%, coverage factor k=2, by fol owing the methods de-scribed in GB/T 21911-2008 ＂Determination of Phthalate Esters in Foods＂. The av-erage DBP concentration in the liqueur of eight repeated measurements was（0.985＆#177; 0.056） mg/kg finaly.
基金Majlesi Branch, Islamic Azad University, for their support
文摘Isoproterenol （ISPR） is an important catecholamine‐based drug that is widely used in the treatment of heart disease. However, overdose of this drug is very dangerous to the human body. In this study, a new sensor based on a pyrogallol red modified‐multiwalled carbon nanotube paste electrode （PGRMMWCNTPE） was prepared and used for high sensitivity determination of ISPR in aqueous solution. Electrocatalytic oxidation of ISPR at the PGRMMWCNTPE was investigated by chronoam‐perometry, cyclic voltammetry, and square‐wave voltammetry. The values of the catalytic rate con‐stant, electron transfer coefficient, and diffusion coefficient for ISPR oxidation were then calculated using voltammetric data. A linear calibration curve was constructed for ISPR concentration in the range 0.8–570μmol/L with a detection limit of 0.47μmol/L ISPR. The sensor was then applied to the determination of ISPR in urine and drug samples with satisfactory results.
文摘Synthesis and separation of asymmetrically octa-substituted phthalocyanines （Pcs） derivatives obtained by cyclotetramerization of two different phthalonitriles （Pns） precursors is described. The phthalonitriles were designed to have different polarity to enable successful chromatographic isolation. The side-chains was designed to lie perpendicular to the plane of the macrocycle via ketal link. It was hoped that the obtained materials would exhibit enhanced solubility and less columnar aggregation both in solution and in the solid state. The preparation of the ketal compounds （2,2-didodecyl- 1,3-benzodioxoles ） with was performed according to Cole method in which catechol and the didodecyl ketone were refluxed in toluene solution in the presence of a catalytic amount of p-toluene sulphonic acid （PTSA）. The resultant water was removed by azeotropic distillation using a Dean-Stark trap. 2,2-didodecyl-l,3-benzodioxoles was brominated then cyanated as described in literature to give the desired phthalonitrile. The other phthalonitrile （4,5-bis（1＇,4＇,7＇,10＇-tetraoxaundecyl） phthalonitrile was obtained also as described in literature. The structures of the obtained isomers were confirmed by spectroscopic methods. Optical microscopy and differential scanning calorimetry （DSC） measurements revealed that two of the obtained derivatives display hexagonal and rectangular columnar liquid crystalline phases （Dhd＆Drd） over a wide temperature range.
基金Supported by the National Natural Science Foundation of China （21106134） and the Natural Science Foundation of Zlaejlang Province （Y4100671）.
文摘2-Methyl-4-methoxyaniline （MMA） was synthesized by one-pot method through the hydrogenation and Bamberger rearrangement of o-nitrotoluene in methanol using acidic ionic liquid and 3% Pt/C as catalyst system. The effects of ionic liquid type, dosage of ionic liquid and 3% Pt/C, reaction temperature and reaction pressure on o-nitrotoluene conversion and MMA selectivity were investigated. The results indicated that the imidazolium-based acidic ionic liquid which contains SO3H-functionalized cation showed higher selectivity to MMA than other acidic ionic liquids used in this work. Using 1-（propyl-3-sulfonate）-3-methylimidazolium hydrosulfate （[HSO3-pmim][HSO4]） as the acid catalyst, the selectivity to MMA was as high as 67.6% at 97.8% of o-nitrotoluene conversion. As 3% Pt/C increased from 0.01 g to 0.025 g, the selectivity to MMA decreased from 73.4% to 62.5%, because of the hydrogenation of intermediate o-methyl-phenylhydroxylamine to o-toluidine becoming more dominant. An increase in hydrogen pressure also had obviously dramatic effect in lowering the MMA selectivity. After easy separation from the products, the catalyst system could be reused at least 3 times.
文摘Amino acid neurotransmitters facilitate the transmission of nerve messages across the synapses and play essential roles in the control and regulation of a variety of functions in the central and peripheral nervous system. In this study, we developed a sensitive and efficient method using high-performance liquid chromatography （HPLC） with fluorescence detection for the assay of five important amino acid n After derivatization with o-phthaldialdehyde （OPA）, aspartate （Asp）, glutamic acid （Glu）, glycine （Gly）, taurine （Tau） and ）,-aminobutyric acid （GABA） were simultaneously detected in the presence of the internal standard homoserine （Hse）. Precise separation of these five amino acids was achieved using isocratic elution within 24 min. Good linearity was found over the concentration range with correlation coefficients （r2） not less than 0.9998. The limit of detection （LOD） values were no more than 10 nmol/L. The intra- and inter-day reproducibility was adequate with the relative standard deviation （RSD） of 10.5% or below. This method has also been applied to the analysis of amino acids in the substantia nigra and striatum samples obtained from C57BL/6 mice.
