摘要
0.1 mol/L KNO3空白液与Cl-切换时, AgCl电极响应的瞬时电位信号峰高度ΔEp有非常好的再现性, 40多天所测的10次标准曲线电位平均偏差小于2.0 mV, ΔEp～p(Cl-)直线平均斜率为55.4 mV, 其平均偏差小于1.0 mV, 电极响应下限和ΔEp～p(Cl-)直线截距都与经AgCl溶度积所计算的值一致. 瞬时信号峰电位上升时间小于1.5 s, 可实现小体积试液的快速准确分析. 用离子水合吉布氏自由能ΔGh(Cl-)的变化解释了瞬时信号不同阶段的电位变化速度. 实验中使用自制的活度阶梯自动切换装置, 该装置具有容积比为 4∶1的空白液和试液两个注射泵. 用该法已测定了维生素B6的含量.
When 0.10 mol/L KNO 3 blank solution and Cl - test solution are switched each other, day to day reproducibility of the peak height Δ E p of transient signal responded by Cl - selective electrode is very good. The detection limit of Cl - selective electrode and the intercept of Δ E p~\%p\%(Cl) straight line accord with both values calculated by K sp (AgCl) respectably. At positive activity step, the jump time of transient signal is smaller than 1.5 s, the fast and accurate analysis of test solution in small volume may be achieved. The potential variance velocity in different stage of transient signal may be explained by the variance of Cl - hydration Gibbs free energy, Δ G h(Cl -)=Δ G 0 h(Cl -)+ RT ln a Cl(H 2O) - n / a 0 p (Cl - g)/ p 0, where a 0=1 mol/L, \%P\% 0=\{1.013×\}10 \{-5\} Pa, Δ G 0 h(Cl -)=-337 kJ/mol. At the start of positive activity step, p (Cl - g) is very small, a Cl(H 2O) - n larger, then ｜Δ G h(Cl -)｜ the smallest. Because the smaller the ｜Δ G h(Cl -)｜, the larger the hydration velocity of Cl(H 2O) - \%n\%, the jump of transient potential is the fastest. At the approach of peak potential, both p (Cl - g) and ｜Δ G h(Cl -)｜ are almost the largest, the dehydration velocity of Cl(H 2O) - \%n\% the smallest, then the jump of transient potential very slow. At the start of negative acitivity step, a Cl(H 2O) - n is almost zero, p (Cl - g) the largest, then ｜Δ G h(Cl -)｜ the largest. Contrary to the dehydration of Cl(H 2O) - \%n\%, the hydration velocity of Cl - g is the largest, then the jump of transient potential from peak potential to positive direction the fastest. With the decrease of p (Cl - g) and the increase of a Cl(H 2O) - n , both the ｜Δ G h(Cl -)｜ and hydration volecity of Cl - g are getting smaller and smaller, so the transient potential tends slowly to the base line.The automatically switching setup of activity step used in this experiment is hom made, the setup is provided with both injectors for blank and test solutions.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第4期556-559,共4页
Chemical Journal of Chinese Universities
基金
国家自然科学基金，陕西省自然科学基金
关键词
氯离子选择电极
瞬时电位信号
活度阶梯法
瞬时电位分析法
离子水合自由能
电极响应
Chloride ion selective electrode
Transient potential signal
Activity step method
Transient potentiometry
Ion hydration free energy
Electrode response mechanism
