This paper reports the results for the pH of three buffer solutions free of chloride ion. The remaining six buffer solutions have saline media of the ionic strength I = 0.16 mol.kg-1, matching closely to that of the p...This paper reports the results for the pH of three buffer solutions free of chloride ion. The remaining six buffer solutions have saline media of the ionic strength I = 0.16 mol.kg-1, matching closely to that of the physiological sample. Conventional paH values for the three buffer solutions without the chloride ion and six buffer solutions with the chloride ion at I = 0.16 mol.kg-1 from 5°C to 55°C have been calculated. The operational pH values for five buffer solutions at 5°C and 55°C have been determined based on the difference in the values of the liquid junction potentials between the blood phosphate standard and the experimental buffer solutions. Five of these buffers are recommended as standards for the physiological pH range 7.5 to 8.5.展开更多
The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffe...The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffer solutions have been evaluated in the temperature range of 5℃ to 55℃ using an extended version of the Debye-Hückel equation. The pH values are reported using 1) the Debye-Hückel extension of the Bates-Guggenheim convention in the tempera- ture range 5℃ to 55℃ and 2) with and without liquid junction correction at 25℃ and 37℃. These TES buffer solutions are recommended as secondary standard references for pH measurements in the range of pH 7.2 to 7.5 for physiological application with an ionic strength of I = 0.16 mol.kg-1.展开更多
Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range ...Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.展开更多
准确检测植物体内的氟含量有助于预测氟化物的生态环境效应。植物中的氟含量低,通常不超过300μg/g,应用离子选择电极法测量氟需选择样品分解效率高的前处理方法使氟不受到损失,获得离子成分简单、空白低的溶液,同时加入适量的缓冲液增...准确检测植物体内的氟含量有助于预测氟化物的生态环境效应。植物中的氟含量低,通常不超过300μg/g,应用离子选择电极法测量氟需选择样品分解效率高的前处理方法使氟不受到损失,获得离子成分简单、空白低的溶液,同时加入适量的缓冲液增强氟离子的强度和掩蔽干扰。本文采用微波消解法处理植物样品,离子选择电极法测定氟的含量,通过优化实验条件确定了缓冲液的浓度。结果表明,在25℃、p H=6.5的样品溶液中加入147 g/L总离子强度缓冲溶液（TISAB）10 m L,避免了溶液中的阳离子与氟离子生成稳定的不溶絮状物,显著降低了沉淀物的产生。本方法检出限为0.242μg/g,精密度（RSD）小于8.5%,回收率为92.0%-108%,能满足地球化学样品分析中对植物样品中低含量氟的检测要求。展开更多
The thermosensitive poly （ N-isopropylacrylamide ） （PNIPAAm） and poly （N-isopropylacrylamide-co-acrylamide） [ poly （NIPAAm-co-AAm） ] hydrogels with different acrylamide molar percentage are prepared by radiati...The thermosensitive poly （ N-isopropylacrylamide ） （PNIPAAm） and poly （N-isopropylacrylamide-co-acrylamide） [ poly （NIPAAm-co-AAm） ] hydrogels with different acrylamide molar percentage are prepared by radiation polymerization using Co^60 γ-ray. Their swelling equilibrium data in the media of deionized water, NaCl aqueous solutions and different pH buffer solutions are determined. It appears that lower critical solution temperature （LCST） of the hydrogels will drop with the increase of ionic strength and increase with the rising of acrylamide content, A semi-empirical formula is set up with the experimental results. Moreover, it also indicates that this copolymer is pH-sensitive, which is similar to the homopolymer of PNIPAAm.展开更多
文摘This paper reports the results for the pH of three buffer solutions free of chloride ion. The remaining six buffer solutions have saline media of the ionic strength I = 0.16 mol.kg-1, matching closely to that of the physiological sample. Conventional paH values for the three buffer solutions without the chloride ion and six buffer solutions with the chloride ion at I = 0.16 mol.kg-1 from 5°C to 55°C have been calculated. The operational pH values for five buffer solutions at 5°C and 55°C have been determined based on the difference in the values of the liquid junction potentials between the blood phosphate standard and the experimental buffer solutions. Five of these buffers are recommended as standards for the physiological pH range 7.5 to 8.5.
文摘The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffer solutions have been evaluated in the temperature range of 5℃ to 55℃ using an extended version of the Debye-Hückel equation. The pH values are reported using 1) the Debye-Hückel extension of the Bates-Guggenheim convention in the tempera- ture range 5℃ to 55℃ and 2) with and without liquid junction correction at 25℃ and 37℃. These TES buffer solutions are recommended as secondary standard references for pH measurements in the range of pH 7.2 to 7.5 for physiological application with an ionic strength of I = 0.16 mol.kg-1.
文摘Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.
文摘准确检测植物体内的氟含量有助于预测氟化物的生态环境效应。植物中的氟含量低,通常不超过300μg/g,应用离子选择电极法测量氟需选择样品分解效率高的前处理方法使氟不受到损失,获得离子成分简单、空白低的溶液,同时加入适量的缓冲液增强氟离子的强度和掩蔽干扰。本文采用微波消解法处理植物样品,离子选择电极法测定氟的含量,通过优化实验条件确定了缓冲液的浓度。结果表明,在25℃、p H=6.5的样品溶液中加入147 g/L总离子强度缓冲溶液（TISAB）10 m L,避免了溶液中的阳离子与氟离子生成稳定的不溶絮状物,显著降低了沉淀物的产生。本方法检出限为0.242μg/g,精密度（RSD）小于8.5%,回收率为92.0%-108%,能满足地球化学样品分析中对植物样品中低含量氟的检测要求。
基金Project Supported by Science Foundation of Shanghai MunicipalCommission of Science and Technology (Grant No .02DJ14030)
文摘The thermosensitive poly （ N-isopropylacrylamide ） （PNIPAAm） and poly （N-isopropylacrylamide-co-acrylamide） [ poly （NIPAAm-co-AAm） ] hydrogels with different acrylamide molar percentage are prepared by radiation polymerization using Co^60 γ-ray. Their swelling equilibrium data in the media of deionized water, NaCl aqueous solutions and different pH buffer solutions are determined. It appears that lower critical solution temperature （LCST） of the hydrogels will drop with the increase of ionic strength and increase with the rising of acrylamide content, A semi-empirical formula is set up with the experimental results. Moreover, it also indicates that this copolymer is pH-sensitive, which is similar to the homopolymer of PNIPAAm.
