元素分析作業(yè)

1、化學(xué)與環(huán)境科學(xué)學(xué)院 分析化學(xué) 20144015016 駱洪偉元素分析的原理及儀器介紹一、元素分析的基本原理1.有機元素定義 有機元素通常是指在有機化合物中分布較廣和較為常見的元素，如碳(C)、氫(H)、氧(O)、氮(N)、硫(S)等元素。2. 元素分析儀測定的原理 待測樣品在高溫條件下，經(jīng)氧氣的氧化與復(fù)合催化劑的共同作用，使待測樣品發(fā)生氧化燃燒與還原反應(yīng)，被測樣品組份轉(zhuǎn)化為氣態(tài)物質(zhì)(CO2, H2O,N2與 SO2)，并在載氣的推動下，進入分離檢測單元。 分離單元采用色譜法原理，利用氣相色譜柱，將被測樣品的混合組份CO2, H2O, N2與SO2 載入到色譜柱中。由于這些組份在色譜柱中流出的時

2、間不同（即不同的保留時間），從而使混合組份按照N,C H,S的順序被分離，被分離出的單組份氣體，通過熱導(dǎo)檢測器分析測量，不同組份的氣體在熱導(dǎo)檢測器中的導(dǎo)熱系數(shù)不同，從而使儀器針對不同組份產(chǎn)生出不同的讀取數(shù)值，并通過與標準樣品比對分析達到定量分析的目的。3. 有機元素分析儀上常用檢測方法 主要有：示差熱導(dǎo)法、反應(yīng)氣相色譜法、電量法和電導(dǎo)法。2、 Vario EL 型元素分析儀介紹1. Function of the varioEL 儀器的功能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.元素分析儀vario EL是一個快速的，用于C、H、N、O、S定量測定的全自動儀器。根據(jù)購買的設(shè)備，儀器能有不同的操作模式，從同一個樣品稱量

4、中同時測定一些元素：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.對元素分析來說，vario EL分析儀的適應(yīng)性根據(jù)樣品可控制的燃燒性和樣品的量。2. General Measuring Principle 通用測量原理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.元素分析儀vario EL工作原理是根據(jù)在氧化的CO2氣氛中和高溫下接觸反應(yīng)的試管燃燒原理工作的。燃燒氣不含雜質(zhì)氣體（例如揮發(fā)性的鹵素）。需測量部分在特殊吸附柱和熱導(dǎo)儀（TCD）連續(xù)測定的幫助下彼此分離。氦（He）用于沖洗和載氣。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 .分析程序的自動控制是通過軟件完成的，樣品特殊氮的是通過指數(shù)（O2指數(shù)15）分配到適合的樣品矩陣。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. 我們將說明一個分析的適時的和功能的過程。在圖示4.1和括弧中的數(shù)字或字母的幫助下，能理解所描述過程的位置。由于所有3個吸附管都是內(nèi)置的（SO2, H2O, CO2），圖示4.1顯示了CH

10、NS模式的簡化的流程圖。根據(jù)操作模式，只有要被測定的元素吸附柱才能列入氣體路線里面。為了使它更清楚，吸附柱不應(yīng)被看作為過渡。 圖4.1 : vario EL （CHNS模式）的流程圖 LegendV2valves for 6ash crucible 灰坩堝V3desorption path SO2 用于解吸附SO2通道的閥7reduction tube 還原管V4O2-input valve O2輸入閥8drying tubes 干燥管V7He-input valve He輸入閥9gas control insert 氣體控制插入V8valves for10flow controller, m

11、easuring side 流量控制器，測量方面V9desorption path H2O用于解吸附H2O通道的閥11detector (TCD) 熱導(dǎo)儀ASO2-adsorption column SO2吸附柱12throttle, reference side 節(jié)流閥，參考方面BH2O-adsorption columnH2O吸附柱13drying tube, reference gas 干燥管，參考氣體CCO2-adsorption columnCO2吸附柱14gauge, gas inlet pressure 量表，氣體入口壓力1Carousel旋轉(zhuǎn)式進樣盤15flowmeter fo

12、r O2 and He 用于O2和He的流量表2ball valve 球閥16gas cleaning tube 氣體清潔試管3combustion tube 燃燒試管17pressure sensor 壓力傳感器43-tube furnace 可容3個試管的加熱爐18drying tube, oxygen 干燥管，氧5O2-lance O2輸入口19needle valve for O2-dosing 用于O2加入的針形閥 4. Sample loading 樣品裝填 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. 均勻分布的微粒樣品包裹在錫箔中，稱重之后放入自動樣品進樣器的旋轉(zhuǎn)式進樣盤中（1）。樣品重量輸入PC中，既可通過界面的在線天平也可用鍵盤手動輸入。樣品名稱和矩陣特殊的加氧量（O2-指數(shù)1-5）被分配到樣品重量中?，F(xiàn)在分析能開始了。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).在分析開始時，測量信號的自動調(diào)零通過檢測器（9）執(zhí)行。之后，球閥（2）的盲孔球以翻轉(zhuǎn)180而打開。旋轉(zhuǎn)式進樣盤（1）升到一個位置，樣品掉入到球閥（2）的盲孔里。球閥旋轉(zhuǎn)90進入沖洗位置，密封了儀器。已進入的大氣中的氮現(xiàn)在被沖洗出來，在沖洗完成之后，樣品以球閥（2）又一次90翻轉(zhuǎn)滴入燃燒管（3）的灰分管（6）中。5.Substance digestion and removal

17、of foreign gases 物質(zhì)消化和干擾氣體的去除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).與樣品進樣程序相同，加氧在灰分管里的通過V4和O2入口（5）開始，以至于樣品掉一個高度氧化的大氣中，并引起爆炸性地燃燒。加氧的轉(zhuǎn)換時間在菜單：“選項參數(shù)”

19、中過程時間“O2延遲”決定。加氧量可用指數(shù)值（19）調(diào)整，對每個單獨的樣品燃燒時間預(yù)先通過PC用O2指數(shù)（1-5）來選擇。After the sample feeding, the integrator reset ensues and the integration display is set to zero. A few seconds thereafter N-integration begins.樣品進樣之后，積分儀重新設(shè)置，積分的顯示又設(shè)置為零。幾秒種之后N-積分開始。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.氧化燃燒時，元素C, H, N和S除了產(chǎn)生分子氮（N2）之外，還有氧化產(chǎn)物O2, H2O, NOX, SO2和SO3。If the sample contains halogens, volatile halogen compounds will be produced.如果樣品含有鹵素，會產(chǎn)生揮發(fā)性鹵素化合物。6.Separation of the measuring components 測量成分

21、的分離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.因為熱導(dǎo)檢測儀不能明確地區(qū)辯出反應(yīng)氣體的不同成分，要測反應(yīng)產(chǎn)物(CO2, H2O, SO2 or N2)必須單獨地沖洗，由載氣（He）一個接一個地送入到測量模式。這個測量成分的分離是通過在加熱柱上（A, B, C）特殊的吸附，吸附柱（A, B, C）和各自分隔的條件與反應(yīng)產(chǎn)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). 在每個操作模式中，只有必要的吸附柱才列入氣體通道中。不被吸附柱影響的氮（N2）是第一個在熱導(dǎo)檢測儀（11）中被檢測的成分（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.當成分的積分法出來時，積分值就儲存起來，積分器就重新啟動，下一個成分被吸附柱吸收并被測量。7.Detection 檢測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.熱導(dǎo)檢測儀（11）由兩個測量池組成。氣流以不變的流量比率穿過它們。載氣流在測量空隙能關(guān)閉,因為測量腔室對氧氣有抵制作用。在操作參考信息時，測量氣流，也就是各自反應(yīng)氣體的解吸附部分（例如He/N2或He/CO2混合物）經(jīng)過另一個的時候，測量池用純載氣He（參考氣流）沖洗。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. 兩個池建立了一個測量橋，它的電的不平衡為在載氣重的氮含量提供了一個直接的標準度。檢測儀輸出電壓以時間功能記錄，然后數(shù)字化，綜合化和以積分表現(xiàn)。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.每個元素通過校準，積分分配到一個絕對的樣品元素含量。從結(jié)果含量和樣品重量中，可以計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.及時的測量過程信號能顯示在顯示器上的功能“ViewGraphic”中。典型的測量峰的圖示在單獨的操作模式中的第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.在開始一個分析之前，要執(zhí)行自動調(diào)零，對檢測儀的零點的浮動的可能進行補償。在氣體成分的每次積分之前，執(zhí)行重新啟動積分器。積分器重新啟動的時間點會通過在參數(shù)菜單中的“積分器重新啟動延遲”

32、受到影響。3、 氧化管和還原管的介紹根據(jù)實驗者的要求，選擇不同的操作模式。各種操作模式應(yīng)該配有不同的實驗要求，具體有以下幾點：加熱爐溫度：不同操作模式下加熱爐溫度不同，錯用溫度會影響還原爐內(nèi)裝填的氧化劑。操作模式：CHNS/CNS/S 燃燒爐：1150 還原爐：850操作模式：CHN/CN/N 燃燒爐：950 還原爐：500操作模式：O 燃燒爐：1150還原管氧化劑的裝填：不同的操作模式選用的氧化劑/還原劑不同。用錯誤的消耗品或一個不適合標準的化學(xué)品的使用會導(dǎo)致受傷或儀器的損壞，也會誤導(dǎo)分析的結(jié)果。（1）CHNS/CNS/S模式A. 燃燒管：同時有硫測定的操作模式時，用底部空的且中部（最熱的區(qū)

33、域）裝有粒狀WO3的試管。石英棉用作中間隔層。作為在粒狀WO3和灰分之間的隔層，用3mm厚的剛玉球。最后安裝灰分和保護試管。如圖3所示。B. 還原管：裝填如圖4所示。只要銀棉表面還有光澤（銀色光澤）使用過的銀棉就還能使用。 圖3 燃燒試管結(jié)構(gòu)示意 圖4 還原管結(jié)構(gòu)示意4、 氧化管和還原管中幾種催化氧化劑的介紹1. 氧化銅 細管狀氧化銅是最早的Pregl經(jīng)典法中所采用的氧化催化劑，直至現(xiàn)在仍被廣泛應(yīng)用。氧化銅性能穩(wěn)定，是可反復(fù)再生使用的高溫氧化劑，有機物在高溫下與氧化銅反應(yīng)，氧化銅部分地被還原為低價氧化物，同時該低價氧化物又立即為氣流中的氧氣活化成氧化銅。氧化銅對一般的有機化合物都能起到很好的氧

34、化作用，但它不具備排除硫、鹵素等干擾元素的能力，僅適用于分析一般的有機化合物。2. 四氧化三鈷四氧化三鈷也是一種氧化性能強且性能穩(wěn)定的高效催化氧化劑。它由高價和低價鈷的氧化物：氧化鈷及三氧化二鈷混合而成，在燃燒過程中能夠連續(xù)釋放出氧化效能比分子氧高得多的原子氧，并被還原成低價鈷的氧化物，同時該低價氧化物又立即與氣流中的氧結(jié)合，可逆地轉(zhuǎn)化為四氧化三鈷。四氧化三鈷的工作溫度以600 為宜，當溫度高于800 時，四氧化三鈷仍具有良好的氧化效能且工作壽命較長，但在高溫下易腐蝕石英管，使其變脆、斷裂。在實踐中應(yīng)用比較廣泛的是鍍銀的四氧化三鈷（Ag+Co3O4），既具有高效的催化氧化性能，又是高效的鹵素、硫吸收劑。3. 五氧化二釩對于易焦化的物質(zhì)，五氧化二釩是一種非常有效的高溫催化氧化劑，它能夠分散樣品顆粒，防止其焦化，同時在有氧氣的條件下循環(huán)式地釋放出氧化性能強的原子氧。某些纖維、塑料及天然