A new detection system consisted of a flame ionization detector（FID） and a sulfur chemiluminescence detector（SCD） was developed for sensitive and interference free determination of total sulfur in natural gas by n...A new detection system consisted of a flame ionization detector（FID） and a sulfur chemiluminescence detector（SCD） was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO_2, CO_2 and H_2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO_2 could be reduced to SO and reacted with O_3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO_2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5 mmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials（GBW 06332 and GBW（E） 061320）.展开更多
The formation of free radicals OH and H in a naturally air-saturated aqueous solution exposed to therapeutic CW ultrasound at a frequency of 820 kHz has been confirmed by using spin trapping 5, 5-dimethyl-1-pyrroline-...The formation of free radicals OH and H in a naturally air-saturated aqueous solution exposed to therapeutic CW ultrasound at a frequency of 820 kHz has been confirmed by using spin trapping 5, 5-dimethyl-1-pyrroline-1-oxide ( DMPO ) and electron spin resonance ( ESR) technique . It is suggested that these radicals are formed due to the high temperature and pressure produced by the ultrasonic transient cavitation. The transient cavitation threshold is found at 0. 537-0.632W/cm2 under a sonication time of 3 minutes .With increasing sound intensity the yield of free radicals OH raises rapidly at the intensity ranging from 1-2W/ cm2, and no longer increase is observed at above 3W/cm2. The sound intensity (Ⅰ) dependence of the yield of OH(D) can be approximately described by a regression equation: D = 8.1(I1/2 -Ic1/2 )1/2 where Ic=0. 667W/ cm2 . Under a fixing sound intensity the yield of OH increases monotonously with the sonication time.展开更多
Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound w...Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound which were well known as reaction products of cyanate esters and epoxy resins, compounds with hybrid ring structure of cyanurate/isocyanurate were determined. Gibbs free energies of the compound having hybrid ring structure of cyanurate/isocyanurate with two isocyanurate moiety were found to be lower than that of the compound with cyanurate ring structure through calculations. Calculation data supported the existence of hybrid ring structure of cy-anurate/isocyanurate. It was revealed that isomerization from cyanurate to isocyanurate occurs via hybrid ring structure of cyanurate/isocyanurate in the reaction of aryl cyanurate and epoxy.展开更多
基金the National Science and Technology Supporting Plan(No.2013BAK12B04)for financial support
文摘A new detection system consisted of a flame ionization detector（FID） and a sulfur chemiluminescence detector（SCD） was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO_2, CO_2 and H_2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO_2 could be reduced to SO and reacted with O_3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO_2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5 mmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials（GBW 06332 and GBW（E） 061320）.
基金The project is supported by Natural Science Foundation of China
文摘The formation of free radicals OH and H in a naturally air-saturated aqueous solution exposed to therapeutic CW ultrasound at a frequency of 820 kHz has been confirmed by using spin trapping 5, 5-dimethyl-1-pyrroline-1-oxide ( DMPO ) and electron spin resonance ( ESR) technique . It is suggested that these radicals are formed due to the high temperature and pressure produced by the ultrasonic transient cavitation. The transient cavitation threshold is found at 0. 537-0.632W/cm2 under a sonication time of 3 minutes .With increasing sound intensity the yield of free radicals OH raises rapidly at the intensity ranging from 1-2W/ cm2, and no longer increase is observed at above 3W/cm2. The sound intensity (Ⅰ) dependence of the yield of OH(D) can be approximately described by a regression equation: D = 8.1(I1/2 -Ic1/2 )1/2 where Ic=0. 667W/ cm2 . Under a fixing sound intensity the yield of OH increases monotonously with the sonication time.
文摘Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound which were well known as reaction products of cyanate esters and epoxy resins, compounds with hybrid ring structure of cyanurate/isocyanurate were determined. Gibbs free energies of the compound having hybrid ring structure of cyanurate/isocyanurate with two isocyanurate moiety were found to be lower than that of the compound with cyanurate ring structure through calculations. Calculation data supported the existence of hybrid ring structure of cy-anurate/isocyanurate. It was revealed that isomerization from cyanurate to isocyanurate occurs via hybrid ring structure of cyanurate/isocyanurate in the reaction of aryl cyanurate and epoxy.
