A new kind of carbazole-based photorefractive polymer was prepared via a post-azo- coupling reaction. The structure of the polymer was characterized by IR, 1H NMR, UV-vis and GPC. The IR and UV-vis spectra demonstrate...A new kind of carbazole-based photorefractive polymer was prepared via a post-azo- coupling reaction. The structure of the polymer was characterized by IR, 1H NMR, UV-vis and GPC. The IR and UV-vis spectra demonstrated that azo group was grafted to the polymer in content of 15.56%. The molecular weight of the polymer as determined by GPC was higher than that of the polymer obtained by common method.展开更多
使用酚二磺酸法、还原蒸馏法、镀铜镉还原-重氮化偶合比色法和改进紫外分光光度法(校正因数法)测定了中国9种不同类型土壤的硝态氮含量,分析了改进紫外分光光度法与其余三种测定方法的差异及其适用性。统计分析表明对于有机质含量低于50...使用酚二磺酸法、还原蒸馏法、镀铜镉还原-重氮化偶合比色法和改进紫外分光光度法(校正因数法)测定了中国9种不同类型土壤的硝态氮含量,分析了改进紫外分光光度法与其余三种测定方法的差异及其适用性。统计分析表明对于有机质含量低于50 g kg-1的矿质土壤,可以使用2.2作为校正因数,四种分析方法的测定值具有极显著的相关性,尤其是紫外分光光度法与酚二磺酸法的测定结果最为接近,没有极显著差异;对于有机质含量接近和高于50 g kg-1的土壤,校正因数还需要修改。紫外分光光度法具有操作简单、测定速度快等优点,适用于批量快速测定。展开更多
In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorpti...In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorptivity(ε496) of 1.7×104L·mol-1·cm-1.A new spectrophotometric approach for nitrite determination was established on such basis with a detection limit of 1.7×10-7 mol/L.Beer’s law was obeyed in the concentration range of 0.05μg/mL-0.80 μg/mL for sodium nitrite.The proposed method has been applied for the determination of nitrite in vegetables,and the results are satisfactory.展开更多
Grignard reagents were prepared from the starting materials 1-bromo-3,5-difluorobenzene,1-bromo-2,4-difluorobenzene andbromo-3,4-difluorobenzene respectively,then reacted with diethyl carbonate to form magnesium tris(...Grignard reagents were prepared from the starting materials 1-bromo-3,5-difluorobenzene,1-bromo-2,4-difluorobenzene andbromo-3,4-difluorobenzene respectively,then reacted with diethyl carbonate to form magnesium tris(difluoropheny)methanol,and methacryloyl chloride was added dropwise to abtain tris(difluorophenyl)methyl methacrylates.The target products were synthesized in high overall yield(67～74%)with"one-pot"method.Structures of the compounds were comfirmed by IR,1HNMR,13CNMR and elemental analysis,and methanolysis was also studied.展开更多
文摘A new kind of carbazole-based photorefractive polymer was prepared via a post-azo- coupling reaction. The structure of the polymer was characterized by IR, 1H NMR, UV-vis and GPC. The IR and UV-vis spectra demonstrated that azo group was grafted to the polymer in content of 15.56%. The molecular weight of the polymer as determined by GPC was higher than that of the polymer obtained by common method.
文摘使用酚二磺酸法、还原蒸馏法、镀铜镉还原-重氮化偶合比色法和改进紫外分光光度法(校正因数法)测定了中国9种不同类型土壤的硝态氮含量,分析了改进紫外分光光度法与其余三种测定方法的差异及其适用性。统计分析表明对于有机质含量低于50 g kg-1的矿质土壤,可以使用2.2作为校正因数,四种分析方法的测定值具有极显著的相关性,尤其是紫外分光光度法与酚二磺酸法的测定结果最为接近,没有极显著差异;对于有机质含量接近和高于50 g kg-1的土壤,校正因数还需要修改。紫外分光光度法具有操作简单、测定速度快等优点,适用于批量快速测定。
文摘In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorptivity(ε496) of 1.7×104L·mol-1·cm-1.A new spectrophotometric approach for nitrite determination was established on such basis with a detection limit of 1.7×10-7 mol/L.Beer’s law was obeyed in the concentration range of 0.05μg/mL-0.80 μg/mL for sodium nitrite.The proposed method has been applied for the determination of nitrite in vegetables,and the results are satisfactory.
文摘Grignard reagents were prepared from the starting materials 1-bromo-3,5-difluorobenzene,1-bromo-2,4-difluorobenzene andbromo-3,4-difluorobenzene respectively,then reacted with diethyl carbonate to form magnesium tris(difluoropheny)methanol,and methacryloyl chloride was added dropwise to abtain tris(difluorophenyl)methyl methacrylates.The target products were synthesized in high overall yield(67～74%)with"one-pot"method.Structures of the compounds were comfirmed by IR,1HNMR,13CNMR and elemental analysis,and methanolysis was also studied.
