氟离子选择电极测定硫铁矿中的氟

硫铁矿中的氟含量,是衡量矿石质量的重要指标之一。本文应用氟离子选择电极测定硫铁矿中的氟,方法简便快速,简化了通常采用的经碱熔蒸馏分离的操作。一、实验方法试剂及仪器见资料,采用HDF-2型氟离子选择电极。标准曲线的绘制:吸取每毫升含0.1毫克氟的标准溶液0.1、0.5、1.0、5.0毫升     

含氟牙膏中氟离子含量的检测——介绍一个开放设计型实验

一个与生活密切相关的开放设计型实验。学生通过查阅文献,对牙膏中氟离子含量的常见测定方法进行综合评述,设计详细实验方案,进行不同方法、不同仪器、不同实验条件的对比,并对各种方法的可行性进行研究。     

氟离子选择电极法测定骨中氟含量

骨中氟含量的测定通常采用较烦琐费时的扩散-比色法。氟离子选择电极的创建是氟化物分析方法的重大发展。Singer等曾应用氟电极测定骨中氟,方法快速而准确,但其操作需要用稀酸碱及醋酸盐小心调节骨样溶液以使其与标准氟溶液具有同一离子强度及pH值。我们采用TISAB技术,以自制Y-1型氟电极测定骨中氟含量,较Singer等所提出的方法更为简便与快速。实验部分 (一)仪器氟电极:自制Y-1型氟离子选择电     

基于“教学评一体化”的化学探究活动一般思路方法建构*——以“物质的分离与提纯”复习课为例

针对学生面对化学实验探究问题无从下手的情况,以物质的分离与提纯这一类探究实验为例,通过“教学评一体化”的教学模式引导学生建立解决“物质分离与提纯”探究实验的一般思路方法。     

(甲基)丙烯酸氟烷基酯的“活性”/可控聚合

带氟烷基侧链的(甲基)丙烯酸氟烷基酯聚合物是一类具有独特表面性能和光学特性的氟聚合物,传统的自由基共聚合由于无法调节聚合物的微细结构和氟原子的分布,限制了该类聚合物在更广领域的应用.活性聚合为聚合物分子设计和合成提供了一个有效方法,利用活性聚合方法可以获得预期结构和性能的含氟嵌段聚合物材料.由于引入了氟烷基侧链,(甲基)丙烯酸氟烷基酯的活性聚合又有其特殊性,本文针对它的活性阴离子聚合、基因转移聚合、活性自由基聚合等方面作一综述.     

氟离子选择电极的修复

由于氟离子选择电极测氟较为成熟,各校的仪器分析实验都选此实验作为电位分析法的教学内容。在离子选择电极中,氟电极价格最昂贵,每支近200元,而使用寿命却不长(厂方规定为一年左右)。据了解,各校都有一批报废氟电极。笔者采用了一些简单修复方法,使我系实验室六支废旧氟电极获得再生,经修复的电极在     

离子选择性电极法测定茶叶及茶水中的氟含量

将经典基础化学实验“离子选择性电极法测定水中微量的氟”实验改进为“离子选择性电极法测定茶叶及茶水中的氟含量”。实验内容由自来水中氟含量测定,拓展到茶叶及茶水氟含量、茶叶氟浸出率的测定;并增加了茶水比、冲泡温度、冲泡时间、冲泡次数、茶叶粒度对茶叶氟浸出率的影响等研究性内容;五大代表性茶样氟含量的测定结果表明,饮用黑茶有氟摄入过量的风险;此外,在离子选择性电极法测氟的应用领域及微量氟的其他检测方法等方面将该实验进一步拓展和延伸。研究性内容的引入及分组实验更有利于培养学生的科研思维和团结协作精神;探索性且具挑战力的实验内容,提高了学生的创新能力及解决实际问题的能力;茶与健康通识内容的渗透,贴近生活,增强了学生的健康意识。本实验内容丰富,趣味性强,易于操作及推广,适合在本科低年级学生中开设。     

用氟离子选择电极测定水泥及其原料中的氟

水泥及其原料中的氟通常采用水蒸气蒸馏-硝酸钍滴定法、锆-茜素红比色法测定,这些方法手续烦杂费时。近年来,操作简便,测定快速的氟离子选择电极在硅酸盐分析方面的应用日趋普遍。为了将这一分析技术应用于水泥分析,我们试验了水泥及原料中氟的测定条件,比较了三种络合缓冲液对铝的掩蔽效果,拟定了定方法。实验与讨论 (一)主要仪器和主要试剂 1.氟离子选择电极:自制,氟化镧     

变量控制在实验探究专题教学中的应用与评价*——以“镁+水”反应体系为例

在以“Mg+H₂O”反应体系为核心的实验探究专题教学活动中,通过变量控制的方法设计实验方案,采用常规实验、数字化实验等方式,多层次探究加速“Mg+H₂O”反应速率的原因和控制条件。在有层次的教学活动中递进式发展学生通过变量控制的方法设计实验方案的能力、拓宽对影响化学反应速率因素的认识角度,通过对活动环节的评价,诊断并发展学生的实验探究能力。     

266nm激光光解间氟溴苯和对氟溴苯

采用266nm紫外激光对间氟溴苯和对氟溴苯进行了光解动力学研究,在多个角度探测了光解碎片Br和C6H4F的时间飞渡谱(TOF)。从光解碎片的平动能分布P(Et)可以得到：间氟溴苯和对氟溴苯大约有46.8%和41.7%的可资用能分配到碎片的平动能,其余的分配到碎片的内能;且各向异性参数被确定为0.7和-0.4。为了更好地解释实验结果,我们利用从头计算方法对反应体系进行了计算,并与实验结果吻合,由此,我们提出了比较合理的光解机理且对氟原子的取代效应进行了讨论。     

国内光催化研究进展简述

分1975~1985, 1985~1995和1995~2012三个时期简要介绍了国内光催化研究进展, 主要侧重于光催化材料及其改性、应用和反应机理方面的研究进展, 并指出了当前光催化领域存在的一些重要问题和未来的发展趋势, 涉及到光解水、CO₂还原、环境净化和选择性有机合成等方面.     

青蒿素研究进展

青蒿素是目前治疗疟疾的特效药。本文对自青蒿素发现以来的最新研究进展进行了比较详尽的综述。内容包括: 青蒿素的发现及历史, 青蒿素的来源, 青蒿素的全合成,青蒿素的生物合成, 青蒿素衍生物以及植物组织培养生产青蒿素。     

Reactions in droplets in microfluidic channels

Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights.     

Interpretation of inorganic arsenic metabolism in humans in the light of observations made in vitro and in vivo in the rat

The toxicity of inorganic trivalent arsenic for living organisms is reduced by in vivo methylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (As_i). In order to document the methylation process in humans, the kinetics of As_i, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of As_i. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As₂O₃) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterized in vitro and in vivo in rats as follows: (1) production of As_i metabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S-adenosylmethionine), lead to the production of mono- and di-methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of As_i uptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic systems.     

Recent Advances in Analytical Methodology for in vivo Electrochemistry in Mammals

Electrochemistry is one of the most advanced techniques for monitoring neurochemical activities in the living brain because electrochemical approaches bear the advantageous features of high spatial and temporal resolutions, which facilitate its tremendous potential in investigating the highly spatially heterogeneous brain system and the fast dynamics of neurochemical activities. On the other hand, since brain is the most complicated organ in the sense of its numerous kinds of neurochemical species, high selectivity is always required for any analytical methods that approach the brain. In this review, we will discuss various electrochemical methodologies to achieve selective detection of neurochemicals in mammalian brain and the strategies developed mainly by our group towards selective monitoring of both electrochemically active and inactive neurochemicals. At the end, we will discuss possible solutions towards brain mapping of neurochemical species and combination of neurochemical detection strategy with electrophysiology as the direction of future development of electroanalysis in living brain.     

乙基香兰素研究前景

报导了近几十年来国内外关于乙基香兰素的研究进展与动态,并简单介绍了本文作者在该方面所取得的研究成果,参考文献33篇。     

Gemini表面活性剂合成进展

系统总结了近百种Gemini表面活性剂的合成路线和方法,并且按照其结构特点分门别类地进行比较和归纳,对今后Gemini表面活性剂的合成发展方向提出了一些看法,这对促进此类新颖表面活性剂的工业化进程将具有指导意义。     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

Trends in education in analytical chemistry

Summary At the session of the WPAC of Fechem on education in analytical chemistry it was concluded that it is now essential to include chemometrics and basic knowledge of computers in all courses on analytical chemistry.

---

Tendenzen in der analytisch-chemischen Ausbildung

Zusammenfassung Bei einer Tagung der WPAC über die Lehre auf dem Gebiet der analytischen Chemie wurde bei der Betrachtung neuer Aspekte festgestellt, daß vor allem Chemometrie und Grundkenntnisse in Computertechnik in die Ausbildung aufgenommen werden sollten.

     

AGET ATRP in the Presence of Air in Miniemulsion and in Bulk

Summary: The recently developed initiation system, activators generated by electron transfer (AGET), is used in atom transfer radical polymerization (ATRP) in the presence of a limited amount of air. Ascorbic acid and tin(II ) 2‐ethylhexanoate are used as reducing agents in miniemulsion and bulk, respectively. An excess of reducing agent consumes the oxygen present in the system and, therefore, provides a deoxygenated environment for ATRP. ATRP of butyl acrylate is successfully carried out in miniemulsion and in the presence of air. During polymerization the radical concentration remains constant. The polymerization reaches over 60% monomer conversion after 6 h, which results in polymers with a predetermined molecular weight = 14 000 g · mol⁻¹ and a low polydispersity ( = 1.23). AGET ATRP of styrene is also successful in bulk in the presence of air, as evidenced by linear semi‐logarithmic kinetics, which leads to polystyrene with an of 13 400 g · mol⁻¹ and a low polydispersity index ( = 1.14).

Appearance of miniemulsion before and after the reducing agent ascorbic acid was added (left); and GPC traces representing molecular weights during the AGET ATRP of BA in miniemulsion in the presence of air (right).