元素分析作业

1、化学与环境科学学院 分析化学 20144015016 骆洪伟元素分析的原理及仪器介绍一、元素分析的基本原理1.有机元素定义 有机元素通常是指在有机化合物中分布较广和较为常见的元素，如碳(C)、氢(H)、氧(O)、氮(N)、硫(S)等元素。2. 元素分析仪测定的原理 待测样品在高温条件下，经氧气的氧化与复合催化剂的共同作用，使待测样品发生氧化燃烧与还原反应，被测样品组份转化为气态物质(CO2, H2O,N2与 SO2)，并在载气的推动下，进入分离检测单元。 分离单元采用色谱法原理，利用气相色谱柱，将被测样品的混合组份CO2, H2O, N2与SO2 载入到色谱柱中。由于这些组份在色谱柱中流出的时

2、间不同（即不同的保留时间），从而使混合组份按照N,C H,S的顺序被分离，被分离出的单组份气体，通过热导检测器分析测量，不同组份的气体在热导检测器中的导热系数不同，从而使仪器针对不同组份产生出不同的读取数值，并通过与标准样品比对分析达到定量分析的目的。3. 有机元素分析仪上常用检测方法 主要有：示差热导法、反应气相色谱法、电量法和电导法。2、 Vario EL 型元素分析仪介绍1. Function of the varioEL 仪器的功能The elementary analyzer varioEL is a fully automatic instrument for a speedy a

3、nd quantitative determination of CHNOS. Depending on the purchased equipment , the instrument can-in different operation modes-determine the following elements simultaneously from one sample weigh-in: CHNS, CNS, CHN, CN, N, and S.元素分析仪vario EL是一个快速的，用于C、H、N、O、S定量测定的全自动仪器。根据购买的设备，仪器能有不同的操作模式，从同一个样品称量

4、中同时测定一些元素：CHNS,CNS,CHN,CN,N,和S。The suitability of the varioEL analyzer for the element analysis depends on the controllable combustibility of the samples or sample quantities.对元素分析来说，vario EL分析仪的适应性根据样品可控制的燃烧性和样品的量。2. General Measuring Principle 通用测量原理The elementary analyzer varioEL works according

5、to the principle of catalytic tube combustion in an oxygenated CO2 atmosphere and high temperatures. The combustion gases are freed from foreign gases (for instance volatile halogen). The desired measuring components are separated from each other with the help of specific adsorption columns and dete

6、rmined in succession with a thermal conductivity detector (TCD). Helium (He) serves as flushing and carrier gas.元素分析仪vario EL工作原理是根据在氧化的CO2气氛中和高温下接触反应的试管燃烧原理工作的。燃烧气不含杂质气体（例如挥发性的卤素）。需测量部分在特殊吸附柱和热导仪（TCD）连续测定的帮助下彼此分离。氦（He）用于冲洗和载气。3. Analysis 分析The automatic control of the analysis procedure is accompli

7、shed through the software and the sample specific nitrogen dosing is allocated through index numbers (O2-Index 1-5) to the appropriate sample matrix. The oxygen dosing can be regulated by the operator .分析程序的自动控制是通过软件完成的，样品特殊氮的是通过指数（O2指数15）分配到适合的样品矩阵。加氧量能由操作者控制。We will now explain the timely and func

8、tional course of an analysis. With the help of illustrations 4.1 and the figures/letters in brackets, it is possible to follow the location of the described process. Illustration 4.1 shows the simplified flow diagram of the CHNS mode, since all three possible adsorption columns (SO2, H2O, CO2) are b

9、uilt in. Depending on the mode of operation, only the adsorption columns of the elements to be determined are built into the gas line. To make it clear, the adsorption columns should not be seen as bridged. 我们将说明一个分析的适时的和功能的过程。在图示4.1和括弧中的数字或字母的帮助下，能理解所描述过程的位置。由于所有3个吸附管都是内置的（SO2, H2O, CO2），图示4.1显示了CH

10、NS模式的简化的流程图。根据操作模式，只有要被测定的元素吸附柱才能列入气体路线里面。为了使它更清楚，吸附柱不应被看作为过渡。 图4.1 : vario EL （CHNS模式）的流程图 LegendV2valves for 6ash crucible 灰坩埚V3desorption path SO2 用于解吸附SO2通道的阀7reduction tube 还原管V4O2-input valve O2输入阀8drying tubes 干燥管V7He-input valve He输入阀9gas control insert 气体控制插入V8valves for10flow controller, m

11、easuring side 流量控制器，测量方面V9desorption path H2O用于解吸附H2O通道的阀11detector (TCD) 热导仪ASO2-adsorption column SO2吸附柱12throttle, reference side 节流阀，参考方面BH2O-adsorption columnH2O吸附柱13drying tube, reference gas 干燥管，参考气体CCO2-adsorption columnCO2吸附柱14gauge, gas inlet pressure 量表，气体入口压力1Carousel旋转式进样盘15flowmeter fo

12、r O2 and He 用于O2和He的流量表2ball valve 球阀16gas cleaning tube 气体清洁试管3combustion tube 燃烧试管17pressure sensor 压力传感器43-tube furnace 可容3个试管的加热炉18drying tube, oxygen 干燥管，氧5O2-lance O2输入口19needle valve for O2-dosing 用于O2加入的针形阀 4. Sample loading 样品装填 The homogenized sample is packed in tin foil, weighed and plac

13、ed into the carousel of the automatic sample feeder (1). The sample weight is entered into the PC either from an on-line balance via an interface or manually with the keyboard. The sample name and the matrix specific oxygen dosing (O2-Index 1-5) is allocated to the sample weight . Now the analysis c

14、an be started. 均匀分布的微粒样品包裹在锡箔中，称重之后放入自动样品进样器的旋转式进样盘中（1）。样品重量输入PC中，既可通过界面的在线天平也可用键盘手动输入。样品名称和矩阵特殊的加氧量（O2-指数1-5）被分配到样品重量中。现在分析能开始了。At the start of an analysis, the Auto-Zero Adjust of the measuring signal is carried out through the detector (9). Thereafter the ball valve (2) opens through a 180 turn o

15、f the blind hole ball. The carousel (1) moves up one position and the sample drops into the blind hole of the ball valve (2). The ball valve (2) turns 90 into flushing position and seals the apparatus. The atmospheric nitrogen that had entered is now flushed out and after flushing is completed, the

16、sample drops into the ash finger (6) of the combustion tube (3) through another 90 turn of the ball valve (2).在分析开始时，测量信号的自动调零通过检测器（9）执行。之后，球阀（2）的盲孔球以翻转180而打开。旋转式进样盘（1）升到一个位置，样品掉入到球阀（2）的盲孔里。球阀旋转90进入冲洗位置，密封了仪器。已进入的大气中的氮现在被冲洗出来，在冲洗完成之后，样品以球阀（2）又一次90翻转滴入燃烧管（3）的灰分管（6）中。5.Substance digestion and removal

17、of foreign gases 物质消化和干扰气体的去除Parallel to the sample feeding procedure, the oxygen dosing in the ash finger (6) begins via V4 and the O2-lance (5), so that the sample drops into a highly oxygenated atmosphere and combusts explosively. The time for switching on the oxygen dosing is determined by the p

18、rocess time “O2-delay“ in the menu OptionsParameters. The oxygen dosing amount is adjusted on the needle valve (19) and the combustion time is selected beforehand for each sample individually by the PC using O2-Index (1-5).与样品进样程序相同，加氧在灰分管里的通过V4和O2入口（5）开始，以至于样品掉一个高度氧化的大气中，并引起爆炸性地燃烧。加氧的转换时间在菜单：“选项参数”

19、中过程时间“O2延迟”决定。加氧量可用指数值（19）调整，对每个单独的样品燃烧时间预先通过PC用O2指数（1-5）来选择。After the sample feeding, the integrator reset ensues and the integration display is set to zero. A few seconds thereafter N-integration begins.样品进样之后，积分仪重新设置，积分的显示又设置为零。几秒种之后N-积分开始。During oxidative combustion ,the elements C, H, N and S p

20、roduce in addition to the molecular nitrogen (N2) the oxidation products O2, H2O, NOX,SO2 and SO3.氧化燃烧时，元素C, H, N和S除了产生分子氮（N2）之外，还有氧化产物O2, H2O, NOX, SO2和SO3。If the sample contains halogens, volatile halogen compounds will be produced.如果样品含有卤素，会产生挥发性卤素化合物。6.Separation of the measuring components 测量成分

21、的分离As the thermal conductivity detector (TCD, 11) cannot specifically distinguish between the different components of the reaction gas, the desired reaction products (CO2, H2O, SO2 or N2) must be flushed individually and one after the other by the carrier gas (He) into the measuring module. This sep

22、aration of measuring components is carried out through specific adsorption on heatable columns (A,B,C), whereby the adsorption columns (A,B,C) and the respective separation conditions are in accordance with a reaction product A = SO2-adsorption column, B = H2O-adsorption column, C= CO2-adsorption co

23、lumn.因为热导检测仪不能明确地区辩出反应气体的不同成分，要测反应产物(CO2, H2O, SO2 or N2)必须单独地冲洗，由载气（He）一个接一个地送入到测量模式。这个测量成分的分离是通过在加热柱上（A, B, C）特殊的吸附，吸附柱（A, B, C）和各自分隔的条件与反应产物相一致（A=SO2吸附柱，B=H2O吸附柱，C=CO2吸附柱）。In each mode of operation only the necessary adsorption columns are built into the gas path.Nitrogen (N2), which is unaffecte

24、d by the adsorption columns is the first component that is measured in the thermal conductivity detector (11) (exception: S-mode). 在每个操作模式中，只有必要的吸附柱才列入气体通道中。不被吸附柱影响的氮（N2）是第一个在热导检测仪（11）中被检测的成分（除了S模式）。When the integration of a component is concluded, the integral value is stored, an integrator reset i

25、s carried out and the next components is desorbed by the adsorption column and measured.当成分的积分法出来时，积分值就储存起来，积分器就重新启动，下一个成分被吸附柱吸收并被测量。7.Detection 检测The thermal conductivity detector (11) consists of two measuring chambers. The gas flows through them at constant rate of flow. The carrier gas flow can

26、be turned off during measurement breaks because the measuring chambers are resistant against oxygen. During operation the reference measuring chamber is flushed with pure carrier gas He (reference gas flow) while the measuring gas flow, i.e. the respectively desorbed fraction of the reaction gas (e.

27、g. He/N2- or He/CO2-mixture) passes through the other one.热导检测仪（11）由两个测量池组成。气流以不变的流量比率穿过它们。载气流在测量空隙能关闭,因为测量腔室对氧气有抵制作用。在操作参考信息时，测量气流，也就是各自反应气体的解吸附部分（例如He/N2或He/CO2混合物）经过另一个的时候，测量池用纯载气He（参考气流）冲洗。The two chambers constitute a measuring bridge and its electrical imbalance provides a direct gauge for the

28、 nitrogen content in the carrier gas. The detector output voltage is recorded as a function of time and then digitized, integrated and represented as an integral. 两个池建立了一个测量桥，它的电的不平衡为在载气重的氮含量提供了一个直接的标准度。检测仪输出电压以时间功能记录，然后数字化，综合化和以积分表现。Through a calibration for each element, the integral is allocated

29、to an absolute element content of the sample. From the resulting content and the sample weight, the percentage of the element content is calculated.每个元素通过校准，积分分配到一个绝对的样品元素含量。从结果含量和样品重量中，可以计算出元素的百分含量。The timely course of the measuring signal can be displayed through the function ViewGraphic on the mo

30、nitor . Illustrations of a typical measuring peak can be seen in chapter 7 under the respective mode of operation.及时的测量过程信号能显示在显示器上的功能“ViewGraphic”中。典型的测量峰的图示在单独的操作模式中的第7章中能看到。Before starting an analysis, an Auto-Zero Adjust is carried out, to compensate a possible zero point drift of the detector.

31、Before every integration of a gas component, the integrator reset to zero is carried out. The point of time of the integrator reset can be influenced through the “Integrator-Reset-Delay“ in the Parameter-menu.在开始一个分析之前，要执行自动调零，对检测仪的零点的浮动的可能进行补偿。在气体成分的每次积分之前，执行重新启动积分器。积分器重新启动的时间点会通过在参数菜单中的“积分器重新启动延迟”

32、受到影响。3、 氧化管和还原管的介绍根据实验者的要求，选择不同的操作模式。各种操作模式应该配有不同的实验要求，具体有以下几点：加热炉温度：不同操作模式下加热炉温度不同，错用温度会影响还原炉内装填的氧化剂。操作模式：CHNS/CNS/S 燃烧炉：1150 还原炉：850操作模式：CHN/CN/N 燃烧炉：950 还原炉：500操作模式：O 燃烧炉：1150还原管氧化剂的装填：不同的操作模式选用的氧化剂/还原剂不同。用错误的消耗品或一个不适合标准的化学品的使用会导致受伤或仪器的损坏，也会误导分析的结果。（1）CHNS/CNS/S模式A. 燃烧管：同时有硫测定的操作模式时，用底部空的且中部（最热的区

33、域）装有粒状WO3的试管。石英棉用作中间隔层。作为在粒状WO3和灰分之间的隔层，用3mm厚的刚玉球。最后安装灰分和保护试管。如图3所示。B. 还原管：装填如图4所示。只要银棉表面还有光泽（银色光泽）使用过的银棉就还能使用。 图3 燃烧试管结构示意 图4 还原管结构示意4、 氧化管和还原管中几种催化氧化剂的介绍1. 氧化铜 细管状氧化铜是最早的Pregl经典法中所采用的氧化催化剂，直至现在仍被广泛应用。氧化铜性能稳定，是可反复再生使用的高温氧化剂，有机物在高温下与氧化铜反应，氧化铜部分地被还原为低价氧化物，同时该低价氧化物又立即为气流中的氧气活化成氧化铜。氧化铜对一般的有机化合物都能起到很好的氧

34、化作用，但它不具备排除硫、卤素等干扰元素的能力，仅适用于分析一般的有机化合物。2. 四氧化三钴四氧化三钴也是一种氧化性能强且性能稳定的高效催化氧化剂。它由高价和低价钴的氧化物：氧化钴及三氧化二钴混合而成，在燃烧过程中能够连续释放出氧化效能比分子氧高得多的原子氧，并被还原成低价钴的氧化物，同时该低价氧化物又立即与气流中的氧结合，可逆地转化为四氧化三钴。四氧化三钴的工作温度以600 为宜，当温度高于800 时，四氧化三钴仍具有良好的氧化效能且工作寿命较长，但在高温下易腐蚀石英管，使其变脆、断裂。在实践中应用比较广泛的是镀银的四氧化三钴（Ag+Co3O4），既具有高效的催化氧化性能，又是高效的卤素、硫吸收剂。3. 五氧化二钒对于易焦化的物质，五氧化二钒是一种非常有效的高温催化氧化剂，它能够分散样品颗粒，防止其焦化，同时在有氧气的条件下循环式地释放出氧化性能强的原子氧。某些纤维、塑料及天然