A sensitive solvent extraction method for the determination of nonamolar concentrations of silicate in natural waters is developed. According to the traditional aqueous silicate method, silicomolybdenum blue formed by...A sensitive solvent extraction method for the determination of nonamolar concentrations of silicate in natural waters is developed. According to the traditional aqueous silicate method, silicomolybdenum blue formed by the reaction between silicate and ammoni- um molydate and reduced by metol-sulfite reagent is extracted by methyl isobutyl ketone. The absorbance can be enhanced substantially up to 10-folds. The detection limit of silicate is 8 nmol/dm^3 , which is one tenth smaller than the traditional method, with the precision of 4.0% at a silicate level of 50 nmol/dm^3 and 3.2% at a silicate level of 6 μmol/dm^3. Comparing the calibration curves in the distilled water and seawater, it can be seen that the salt effect also exists in the extraction method. However, the salt effect is a linear function of the salinity and can be corrected by simple calibration. The proposed method is successfully applied to the determination of silicate in natural waters. Natural concentrations of arsenate, arsenite and phosphate cause negligible interference.展开更多
Piperonyl methyl ketone was obtained by oxidizing isosafrole with hydrogen peroxide and formic acid. Dianion of ethyl acetoacetate reacted with piperonyl methyl ketone and 5, 6-dihydro-6-methyl-6-piperonyl-2H-pyran-2...Piperonyl methyl ketone was obtained by oxidizing isosafrole with hydrogen peroxide and formic acid. Dianion of ethyl acetoacetate reacted with piperonyl methyl ketone and 5, 6-dihydro-6-methyl-6-piperonyl-2H-pyran-2, 4-dione was prepared, which reacted with substituted anilines in the presence of ethyl orthoformate to obtain 3-anilinomethylene-5, 6- dihydro- 6-methyl-6-piperonyl-2H-pyran-2, 4-diones. Their structures were confirmed by 1HNMR and elemental analysis.展开更多
Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been...Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been studied for the first time.The influence of initial concentration of target compound,solution pH and scavengers on percentage degradation was evaluated.100%removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment,respectively.The first order rate constant of toluene and MIBK degradation(for 200 mg/L each)was 0.421 and 0.319 min~(-1)respectively when they were treated individually,and these values decreased slightly during degradation of their mixture.MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK.The effect of initial concentration of toluene and MIBK showed different degradation patterns.Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers.·OH radical was the major reactive species involved in their degradation.Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter.The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated.The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.展开更多
A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugat...A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugated polyenic acid, methyl benzoate, methyl phenyl ketone,benzonitrile and aniline is proposed, and various quantum parameters of molecular ions ofaromatic conjugated polyenic compounds, together with their framents are calculated bymeans of CNDO/2 method. Through the process of calculation, the peak-height of mass spectracan be quantitatively interpreted, which means that the main factors which influence the cleftforms of simple cleavage of mass spectra of conjugated compounds given by the authorsmight be true to some extent.展开更多
Aerobic oxidation of methyl vinyl ketone to acetal in supercritical carbon dioxide are achieved in high conversion and high selectivity when oxygen pressure reaches to 0.5 MPa. The effects of cocatalysts, additive, pr...Aerobic oxidation of methyl vinyl ketone to acetal in supercritical carbon dioxide are achieved in high conversion and high selectivity when oxygen pressure reaches to 0.5 MPa. The effects of cocatalysts, additive, pressure and temperature of the reaction are studied in detail.展开更多
Herein,a rapid alkenylation of quinoxalin-2(1H)-ones enabled by a combination of Mannich-type reaction and solar photocatalysis is demonstrated.A wide range of functional groups are compatible,affording the correspond...Herein,a rapid alkenylation of quinoxalin-2(1H)-ones enabled by a combination of Mannich-type reaction and solar photocatalysis is demonstrated.A wide range of functional groups are compatible,affording the corresponding products in moderate-to-good yields.Control experiments illustrate that the in situ generated^(1)O_(2)plays a central role in this reaction.This green and efficient strategy provides a practical solution for the synthesis of potentially bioactive compounds that containing a 3,4-dihydroquinoxalin-2(1H)-one structure.展开更多
A method for the determination of iodine based upon compound H2HgI4, formed between I- and Hg1+ in nitric acid and extracted in methyl isobutyl ketone(MIBK), was developed via atomic fluorescence spectrometry(AFS...A method for the determination of iodine based upon compound H2HgI4, formed between I- and Hg1+ in nitric acid and extracted in methyl isobutyl ketone(MIBK), was developed via atomic fluorescence spectrometry(AFS). After the compound is reduced with potassium borohydrid(KBH4), the resultant mercury vapor was injected into the instrument and iodine was, therefore, indirectly determined. Experimental parameters such as the conditions of extraction reagents, aqueous phase acidity, elemental mercury diffusion temperature in a vial and other factors were investigated and optimized. Under the optimum experimental conditions, this method shows a detection limit of 0.038μg/L iodine and a linear relationship between 0.04-20 p.g/L. The method was applied to determining the iodine content in marine duck eggs, kelps, laver and Ganoderma lucidum spirulina, showing a relative standard deviation(RSD) of 2.15% and the recoveries in the range of 98.1%-102.5%.展开更多
基金The National Science Foundation of China under contract No.40606028the Special Fund from the National Key Basic Research Program of China under contract No.2006CB400601.
文摘A sensitive solvent extraction method for the determination of nonamolar concentrations of silicate in natural waters is developed. According to the traditional aqueous silicate method, silicomolybdenum blue formed by the reaction between silicate and ammoni- um molydate and reduced by metol-sulfite reagent is extracted by methyl isobutyl ketone. The absorbance can be enhanced substantially up to 10-folds. The detection limit of silicate is 8 nmol/dm^3 , which is one tenth smaller than the traditional method, with the precision of 4.0% at a silicate level of 50 nmol/dm^3 and 3.2% at a silicate level of 6 μmol/dm^3. Comparing the calibration curves in the distilled water and seawater, it can be seen that the salt effect also exists in the extraction method. However, the salt effect is a linear function of the salinity and can be corrected by simple calibration. The proposed method is successfully applied to the determination of silicate in natural waters. Natural concentrations of arsenate, arsenite and phosphate cause negligible interference.
文摘Piperonyl methyl ketone was obtained by oxidizing isosafrole with hydrogen peroxide and formic acid. Dianion of ethyl acetoacetate reacted with piperonyl methyl ketone and 5, 6-dihydro-6-methyl-6-piperonyl-2H-pyran-2, 4-dione was prepared, which reacted with substituted anilines in the presence of ethyl orthoformate to obtain 3-anilinomethylene-5, 6- dihydro- 6-methyl-6-piperonyl-2H-pyran-2, 4-diones. Their structures were confirmed by 1HNMR and elemental analysis.
基金the financial support received from Department of Science and Technology(DST),Government of India(Nos.DST/TM/WTI/WIC/2K17/82(G)and DST/CCP/Co E/141/2018(G))for this study。
文摘Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been studied for the first time.The influence of initial concentration of target compound,solution pH and scavengers on percentage degradation was evaluated.100%removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment,respectively.The first order rate constant of toluene and MIBK degradation(for 200 mg/L each)was 0.421 and 0.319 min~(-1)respectively when they were treated individually,and these values decreased slightly during degradation of their mixture.MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK.The effect of initial concentration of toluene and MIBK showed different degradation patterns.Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers.·OH radical was the major reactive species involved in their degradation.Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter.The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated.The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.
文摘A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugated polyenic acid, methyl benzoate, methyl phenyl ketone,benzonitrile and aniline is proposed, and various quantum parameters of molecular ions ofaromatic conjugated polyenic compounds, together with their framents are calculated bymeans of CNDO/2 method. Through the process of calculation, the peak-height of mass spectracan be quantitatively interpreted, which means that the main factors which influence the cleftforms of simple cleavage of mass spectra of conjugated compounds given by the authorsmight be true to some extent.
文摘Aerobic oxidation of methyl vinyl ketone to acetal in supercritical carbon dioxide are achieved in high conversion and high selectivity when oxygen pressure reaches to 0.5 MPa. The effects of cocatalysts, additive, pressure and temperature of the reaction are studied in detail.
基金the Natural Science Foundation of Zhejiang Province(No.LY21B060009)the National Natural Science Foundation of China(No.21871071)for financial support.
文摘Herein,a rapid alkenylation of quinoxalin-2(1H)-ones enabled by a combination of Mannich-type reaction and solar photocatalysis is demonstrated.A wide range of functional groups are compatible,affording the corresponding products in moderate-to-good yields.Control experiments illustrate that the in situ generated^(1)O_(2)plays a central role in this reaction.This green and efficient strategy provides a practical solution for the synthesis of potentially bioactive compounds that containing a 3,4-dihydroquinoxalin-2(1H)-one structure.
文摘A method for the determination of iodine based upon compound H2HgI4, formed between I- and Hg1+ in nitric acid and extracted in methyl isobutyl ketone(MIBK), was developed via atomic fluorescence spectrometry(AFS). After the compound is reduced with potassium borohydrid(KBH4), the resultant mercury vapor was injected into the instrument and iodine was, therefore, indirectly determined. Experimental parameters such as the conditions of extraction reagents, aqueous phase acidity, elemental mercury diffusion temperature in a vial and other factors were investigated and optimized. Under the optimum experimental conditions, this method shows a detection limit of 0.038μg/L iodine and a linear relationship between 0.04-20 p.g/L. The method was applied to determining the iodine content in marine duck eggs, kelps, laver and Ganoderma lucidum spirulina, showing a relative standard deviation(RSD) of 2.15% and the recoveries in the range of 98.1%-102.5%.