简易修正卡尔-费休滴定法测定甲醇中的水分含量

最常用的水含量测定技术是卡尔-菲舍尔滴定法,它需要专门的设备。当没有适当的设备时,该方法可以通过目测滴定终点来实现,这不允许对有色样品进行分析。在这里,选择东方中海油生产的优级甲醇,通过分光度法检测。滴定终点,适用于甲醇样品的水分测定。反应发生在密封的4 mL容器中。检测波长为520nm。滴定终点根据标准ASTM E1064-16制定,根据滴定体积绘制吸光度图。该方法具有较好的重现性(RSD=4.3%)、准确度和线性(R^2=0.997)。

气相色谱与化学发光检测器连用测定石脑油中5种噻吩类硫化物的研究

建立GC-SCD测定石脑油中5种噻吩类硫化物的方法,采用一系列混合标样分别建立相应的标准曲线,研究该方法的准确度和精密度。结果表明,噻吩、2-甲基噻吩、3-甲基噻吩、5-甲基苯并噻吩、3-甲基苯并噻吩浓度在2.5~100mg/L范围内,浓度与峰面积成良好的线性关系,相关系数R^2为0.99599~0.99945,检出限0.24~0.37 mg/L。采用浓度为20 mg/L的混合标样进行精密度的考察,精密度为0.39%~0.88%。与其他检测方法比较,该方法操作简单,检测时间短,稳定性高,精密度高。

能量色散X射线荧光快速测定燃料油中铝、锌、钙、钒、铁和镍含量

建立能量色散X射线荧光法快速测定燃料油六种金属元素质量分数的方法,采用6种金属元素标样分别建立相应的金属元素标准曲线,研究该方法的准确度和精密度和该方法与其他方法的对比。结果表明,6种金属元素质量分数在0~100 mg·kg-1范围内,金属元素质量分数与信号值具有良好的线性关系,其相关系数R2都大于0.9995,以标样浓度为50mg·kg-1平行进样6次,进行精密度的考察,该精密度为0.35%~1.60%。与ICP-AES碱熔法比较,两种检测结果基本一致,说明该方法快速检测燃料油中6种金属质量分数具有良好的稳定性和可行性。与其他检测方法比较,该方法操作简单,检测时间短,容易推广。

Role of PI3K/Akt signaling in the protective effect of magnesium sulfate against ischemia-perfusion injury of small intestine in rats

Background The protective effects of magnesium sulfate against ischemia-reperfusion injury of the small intestine in Sprague-Dawley （SD） rats have been confirmed in our previous research. However, its exact mechanism is unclear. This study was to evaluate the role of PI3K/Akt signal pathway in the protective effect of magnesium sulfate against ischemia-reperfusion injury of the small intestine in SD rats. Methods Rat model of intestinal ischemia-reperfusion injury was used. The SD rats were divided into four groups randomly： sham operation group, ischemia-reperfusion group, magnesium sulfate group and magnesium sulfate plus LY294002 （an inhibitor of PI3K） group. The pathological changes of intestinal mucosa were examined; the activity of diamine oxidase （DAO） in plasma, the plasma contents of malondialdehyde （MDA）, and apoptosis rate of the intestinal mucosal cells were determined and compared. The expression of p-Akt was detected by Western blotting. Results There were more evident pathological changes of the intestinal mucosa （higher Chiu＇s score, P 〈0.05）, enhanced DAO activity （P 〈0.05）, elevated contents of MDA （P 〈0.05）, higher apoptosis rate （P 〈0.05）, and lower level of p-Akt （P 〈0.05） in the ischemia-reperfusion group compared with the sham operation group. There were less evident pathological changes of the intestinal mucosa （lower Chiu＇s score, P 〈0.05）, lower DAO activity （P 〈0.05）, lower contents of MDA （P 〈0.05）, and lower apoptosis rate （P 〈0.05）, but higher level of p-Akt （P 〈0.05） irL the magnesium sulfate group compared with the ischemia-reperfusion group. There were more evident pathological changes of the intes,inal mucosa （higher Chiu＇s score, P 〈0.05）, higher contents of MDA （P 〈0.05）, higher DAO activity （P 〈0.05） and higher apoptosis rate （P 〈0.05）, and lower level of p-Akt （P 〈0.05） in the magnesium sulfate plus LY294002 group compared with the magnesium sulfate group. Conclusions Activation of PI3K/Akt signal pathway results in the reduction of cell apoptosis, which likely accounts for the protective effect of magnesium sulfate against intestinal ischemia-reperfusion injury.