共查询到19条相似文献,搜索用时 140 毫秒
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以酶法提取茵陈中黄酮类化合物,用紫外-可见比色法和芦丁为标准品测定茵陈总黄酮的得率,研究酶用量、pH值、温度、乙醇浓度、提取时间对黄酮得率的影响。最佳工艺条件为纤维素酶的浓度0.10 mg/mL,pH=4.2,温度50℃,乙醇浓度为60%,恒温振荡1.5 h,此条件下黄酮的得率为3.513%。 相似文献
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以不同浓度的硅酸钠、碳酸钠及二者混合物作稳定剂,研究它们对有效氯含量为0.5%(质量分数,下同)的次氯酸钠溶液化学稳定性的影响。测定稳定化处理后次氯酸钠溶液中有效氯的含量,结果表明:54 ℃下恒温密闭静置14 d后,加入硅酸钠、碳酸钠以及二者混合物作稳定剂的次氯酸钠溶液的有效氯,最高分别可保留初始浓度的88.16%、86.81%和92.85%;而不加任何稳定剂的次氯酸钠溶液在同样条件下其有效氯含量仅仅可保留初始浓度的76.58%。实验结果表明,硅酸钠和碳酸钠的混合物可以作为次氯酸钠溶液的良好稳定剂。 相似文献
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准确分析浓海水中溴离子的浓度具有现实意义.系统介绍现今常用的几种分析方法,并分别探讨其各自的优缺点,以供在不同的条件和要求下选择适宜的分析方法.这些分析方法主要有:甲基橙目视比色法,离子选择性电极法,紫外可见分光光度法以及离子色谱法.目前只单纯使用以上分析方法,难以实现高标准的精确度和准确度,因此对浓海水的预处理也相应... 相似文献
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按ISO 7393/2用DPD(N,N-二乙基-1,4-苯二胺)比色法测定循环冷却水中余氯时,用KIO_3-KI作为标准溶液,其校准曲线的试验操作要求十分严格。本文对此进行了理论分析与试验研究,并同时用氯胺T作为标准溶液进行了对比试验。研究结果证明,二者具有较好的一致性,但氯胺T校准曲线试验操作要求不太苛刻,重复性也好,故两种方法都可采用。 相似文献
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用抗坏血酸-磷钼蓝分光光度法测定烷基磷酸酯中的有效磷。有效磷=总磷-无机磷。考察了检测波长、显色剂用量、硫酸加入量及显色时间等测定条件对测定结果的影响。方法最佳测定条件为:检测波长820nm;硫酸(9.58 mol.L-1)、钼酸铵(60 g.L-1)、抗坏血酸(100 g.L-1)的加入量分别为2.00、2.00、1.00 mL,70℃水浴条件下显色20 min。在该条件下,测定吸光度值与质量浓度呈线性关系,总磷测定回归方程为:A=0.1924ρ+0.0134,相关系数r=0.999 5;无机磷用正戊醇萃取法测定,回归方程为:A=0.1846ρ+0.0094,相关系数r=0.999 1。方法回收率为91%~97%,RSD小于3.4%。该方法操作简单、计算方便,有望应用于磷酸酯生产的质量控制。 相似文献
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利用DPD分光光度法测定生活饮用自来水的余氯含量。研究了不同浓度标准溶液吸光度随测定时间和温度的变化关系,从而确定了适宜的测定条件:测定时间10min以内,温度20℃。 相似文献
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根据国际标准ISO 7393/2 DPD比色法测定水中余氯的原理,研究了它的测试方法,特别是用KIO_3-KI绘制校准曲线方法并对其存在问题提出了改进,试验验证结果证明所提改进方法可以消除一氯胺对游离氯测定的干扰,其较准曲线重复性较好。 相似文献
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An electrochemical study on Al-brass alloy (76% Cu, 22% Zn, 2% Al) was conducted. The study focused on determining the corrosion susceptibility of the alloy in seawater in the absence and presence of manganese and chlorine in a stagnant condition. The results show that the addition of Mn from 0.5-5 ppm in seawater increases the corrosion current density of the Al-brass compared to samples tested only in seawater. In contrast, the addition of Cl2 from 0.5-4 ppm slightly improves the corrosion resistance of the alloy in seawater. 相似文献
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In conventional reverse osmosis processes for seawater desalination, a disinfection of the process stream with chlorine compounds is carried out for antifouling. After disinfection the reduction agent Na2S2O5 is used for the removal of residual chlorine in a strongly overstoichiometric way in order to protect the membranes from oxidational damages. To save chemicals a controlled dosing of Na2S2O5 based on a reliable concentration measurement is desirable. Therefore, a measuring method for the determination of the sulfur(IV) components bisulfite and sulfite in seawater is developed based on the combination of UV spectroscopy and a PLS regression method. Experimental results as well as the development of the regression model for sulfur species in ultrapure and seawater is described. 相似文献
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叙述了阻燃聚氨酯软质泡沫塑料中氯含量的测定方法:在助燃剂存在下,氧瓶燃烧使聚氨酯软质泡沫塑料中的有机氯转化为HCl,用稀NaOH吸收,使用硫氰酸汞分光光度法测定聚氨酯软质泡沫塑料中阻燃剂的氯含量。该方法简单快捷、精确度高,回收率为99.64%~102.41%。 相似文献
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The main trouble in the RO method of seawater desalination is biological fouling (bio-fouling) from microorganism growth. In this work, the growth rate of microorganisms in the Red Sea and sterilization by chlorine injection were measured and quantified. Furthermore, actual demonstration of RO pilot tests using cellulose tri-acetate (CTA) RO membranes with chlorine resistance was performed in RO plants where bio-fouling actually occurred. By carrying out direct chlorine sterilization of the RO membrane with an intermittent chlorine injection method, bio-fouling was eliminated. The combination of the CTA membrane and chlorine injection successfully prevented increases of differential pressure and stabilized product water quantity and quality. 相似文献