Sensitive Ion‐Flotation Separation of Ag(I) Traces Using 2‐(2‐Methoxyphenyl)benzimidazole before Flame Atomic Absorption Spectrometric Determination in Water

A sensitive, reliable, and environmentally friendly method for simple separation and preconcentration of Ag(I) traces in aqueous samples is presented prior to their flame atomic absorption spectrometric determinations. At pH 7.0, Ag(I) was separated with 2‐(2‐methoxyphenyl)benzimidazole (MPBI) as a new complexing agent and floated after adding sodium dodecyl sulfate (SDS) as a foaming reagent. The floated layer was then dissolved in proper amount of concentrated nitric acid in methanol and introduced to the flame atomic absorption spectrometer (FAAS). The effects of pH, concentration of MPBI, type and amount of surfactant as the floating agent, type and amount of eluting agent, and influence of foreign ions on the recovery of the analyte ion were investigated. Also, using a nonlinear curve fitting method, the formation constant of 1.62 × 10⁶ was obtained for Ag(I)–MPBI complex. The analytical curve was linear in the range of 1.8 × 10^?7–1.7 × 10^?6 mol/L for determination of Ag(I). The relative standard deviation (RSD; N = 10) corresponding to 0.7 × 10^?6 mol/L of Ag(I), the limit of detection (10 blanks), and the enrichment factor were obtained as 1.7%, 2.9 × 10^?8 mol/L, and 43.0, respectively. The proposed procedure was then applied successfully for determination of silver ions in different water samples.     

东方百合低温打破休眠期间碳水化合物及呼吸代谢变化

以东方百合“西伯利亚”为试材,对不同温度（25 ℃和4 ℃）处理下百合外部及内部鳞片的碳水化合物含量和呼吸代谢途径的关键酶进行了测定。结果表明,随着储藏时间的延长,百合淀粉含量不断下降,可溶性糖含量在低温处理中期较高,且外部鳞片变化较内部鳞片变化剧烈,4 ℃低温处理糖化比25 ℃明显;在百合休眠期间,3条主要呼吸代谢途径的关键酶--糖酵解（EMP）途径的丙酮酸激酶（ATP）、三羧酸循环途径（TCA）的琥珀酸脱氢酶（SDH）和磷酸戊糖途径（PPP）的葡萄糖六磷酸脱氢酶（G6PDH）呈现不同的变化趋势。根据不同途径关键酶的变化趋势判断,处理前30 d,3条主要呼吸途径变化较剧烈,EMP占绝对优势且不断升高,TCA和PPP呈不断下降过程,且内部鳞片变化比外部鳞片明显;其后随着休眠处理时间的延长,EMP不断下降,而TCA和PPP不断得到活化;呼吸强度变化趋势与碳水化合物自然休眠解除的进程基本一致。     

地震条件下挡土墙主动土压力及其分布的统一解

在非地震主动土压力公式的基础上,用微分薄层法给出了地震条件下主动土压力公式,其中填土面倾斜、墙背倾斜、填土为黏性土、墙背与填土间同时存在凝聚力c和内摩擦角? 作用、墙后破裂体存在水平向和竖向的地震加速度,目前所见的地震情况下和非地震情况下的主动土压力均是此公式的特例。对上述同一条件下的挡墙用过墙踵的整块破裂体作静力平衡分析（如库仑分析）,得到的总土压力与文中微分薄层法得到的总土压力大小相等,但微分薄层法作用点位置明显增加,研究表明：设计抗震和非抗震各类挡墙时要引起足够的重视。