501型氨气敏电极说明书Word下载.docx

1、本电极测定氨的线性范围为110-5M110-1M，检测下限约为510-6M，适于室温（不高于40）使用。氨气敏电极由电极外腔管（已装上一透气膜，未装入中解液）及内部电极对两部分组成。并随同电极附有气透膜。（一） 电极组装与保存电极组装步骤如下： （1）装置前先将固定螺帽（13）松开。取出内部玻璃电极，并浸泡在0.1M氯化铵溶液中1小时以上。（2）配制中介液（0.1M氯化铵），亦可根据使用时的特殊条件。采用其他成份的中介液，其要求是：氯离子活度恒定，铵离子浓度较测试过程中形成的NH3浓度高，PH缓冲容量尽可能小，总离子强度尽可能与外部被测试液接近，但应注意在浓度较大的碱金属盐溶液中PH玻璃电极响

2、彻云响应较迟缓。 （3） 装入气透膜，电极第一次使用时可用于原已装好的气透膜，如发现原装上的气透膜已破裂，或用久后不能使用时，可先将固定螺帽（13）松开并取出玻璃电极后，再将垫圈（8）处外腔管上。下部（10.7）接副螺纹松开，并将内套管（6）从外腔管下部（7）中取出，同时取垫圈（4），将原装在电极上的气透膜（1）弃去，洗净各部件，用滤纸吸干，取气透膜一片置于电极外腔管下部（7）上端开口处使其同心，放上垫圈（4）使与外腔管口对准，以内套管96）对准垫圈（4）压入外腔管（7）内，将垫圈（8）外接口螺纹按原方式旋紧，气透膜光滑的一面宜朝外，另一面朝内接触玻璃电极敏感膜。气透膜装好后，可盛纯水或中介液

3、，观察是否漏水，如有漏隙，应另取膜重装。（4）装入电解液及敏感受电极，将装好膜的电极管中介液洗涤，洗涤时可将平头玻璃电极及银/氯化银电极套入同时洗耳恭听涤，然后在管内装入约2毫升中解液。将玻璃电极按原方式插入。固定螺帽锁紧电极，观察玻璃电极敏感膜应紧贴气透膜，电极此时即已装好。（5）电极装好后，浸入0.1M氯化钠溶液中保存备用如电极组装时采用了其他成份的中介液，则保存电极可用与之同时离子强度的氯化钠溶液，应防止保存电极的溶液浓缩干涸，保存液的作用是防止电极内部的中介液薄层溶液因渗透透压变化而稀释或浓缩以致杨份变化，电极装成后，先在保存液中浸泡再行使用，电位值重现性较好，电极长期不使用时，宜取出

4、电极干放保存。（二） 校正曲线的绘制：标准溶液用经105干燥的氯化铵配制，较低浓度的标准液宜临用时配制，并宜采用新鲜制得的去离子水。分别用铵盐浓度为0.1，1，10，100毫克/升的标准溶液50毫升于小烧杯中，（或取实际分析中所需浓度区间的溶液）。在电磁搅拌下插入氨电极（注意电极端部应无气泡附着）。准确加入1毫升10M氢氧化钠，读取平衡电位值，电极插头必须保持清洁与干燥，以保证绝缘性能良好，否则将严重影响测定结果，测试一种溶液后用纯水冲洗电极，必要时可将电极浸入盛有纯水的小烧杯中，在电磁搅拌下观测。至电极电位值恢复至空白值，或稍低于本实验系列中最低标准液应有的电位值。（三） 试样分析 （1）水

5、中氨氮的测定，取水样按（二）所述方法即可进行分析，如水中二价以上离子浓度较高，可在加入氢氧化钠之前先加少量EDTA，标准液中亦补加同量EDTA，EDTA可防止金属氢氧化物沉淀，但用量过多时应补加碱防止PH值下降，水样中有少许泥砂混浊或有色物质对测定无影响，但意含表面活性物质，因其浸渍气透膜，影响其疏水性能。（2）其它试样分析，空气中氨可用0.1M硫酸吸收，然后加碱测定，土壤中氨氮可用电解质溶液浸取，然后加碱测定，煤等试样中的总氮可用凯氏法消化后，不以蒸馏直接用电极法测定，硝酸盐氮可用节瓦德合金鱼学原后，用氨电极测定，详细方法此处从略。（四） 注意事项与故障的排除 （1）电极组装时，玻璃电极敏感

6、膜与气透膜之间的紧压程度应调节得当，接触过松时，则地者间形成的液膜可能过薄而不连续，电位值漂移不稳定，液接电位增大，且膜可能破裂。 （2）电极测试较浓试液后，转测稀溶液时电位值迟效应较显著。故宜按（二）所述，每测一未知液前，先使电位值恢复至一定水平，有可能时应先测衡溶液，再测较浓溶液。电极久置不用后，再使用时，宜先接触（粗液）一较浓试液，用水洗净后再用于测定，能改善其重现性，但如待测试液均是极稀溶液，则不宜用浓试液接触，测定可在小烧杯中进行，不必密封，但为防止氨逸失，宜在电杉插入试液后，再加碱搅拌读数，如需重复测定某一试液，应重新取样，测试低浓度试样，实验室应防止氨的污染。（如吸烟等）。（3）

7、泥砂等一般污浊不影响电极工作，但表面活性物质可使气透膜浸渍清水，应尽量避免。遇这类试液且其氨氮含量不过低（例如1毫克/升以上）时。可将试液装在密封小瓶中，在电磁搅拌下，将电极稍离液面在密封下测定，用这种气隙方式测定，平衡时间较长。（4）复杂试样用校正可见曲线法难于取得精确结果时，可用加入法操作，与一般离子电极的加入法相同。表1例举几种可能的故障及排除方法。在出现故障时，还应注意测试仪器可能发生的故障和漂移。故障及排除方法表1 故 障可 能 原 因排 除 方 法电位值不稳定加碱后电位值急剧上升气透膜破裂，外部碱液渗入中介液薄层。更换气透膜电极不通电，电位测不出（1）中介液量过少，或内部PH膜处有

8、气泡。（2）电极插头与离子计插孔不合或断路。（1）补充中介液，固定玻璃电极之前，上下移动消除气泡。（2）检查并保证接触良好；对某些仪表，需将电极插头的地端与仪表的参比电极插座用导线连接。电位不稳定，不定方向漂移或指针抖动气透膜与玻璃电极膜过于紧贴，形成的液面不连接稍调松固定螺帽（13）电极电位无法恢复至空白或较低值电极在较浓氨试液中测试浸入时间过长。如用水浸泡仍无法复原可将玻璃电极松动再行固定。测试同一种浓度试淮电位值不重现测试前未将电极用纯水浸洗，使电位值恢复至一定数值，迟滞效应的影响。水洗过度对低浓度测定重现性亦有影响。除每次测未知液前均应用纯水浸洗电极，使电位值恢复至一定水平外，在测试各

9、试液前，先粗测接触一待测液中最高浓度的试液能改善电位重现性。江苏江分电分析仪器有限公司Type 501Ammonia Gas-sensing ElectrodeInstruction ManualThis electrode is an electrochemical sensor used for measuring the dissolved ammonia and ammonium salt in aqueous solution. It maybe as well used for the determination of nitrate-nitrogen, total nitroge

10、n, organic nitrogen etc. Its construction is shown in figure 1. A gas-permeable membrane （1） is fitted on the base of tube. In tube the middle electrolyte （internal electrolyte） （5） is filled. The internal sensitive elements consist of a glass electrode with flat head （12） and a silver/silver chlori

11、de electrode （9）. The pH sensitive glass membrane （3） on the flat head is screwed down on to the membrane （1） so that it sandwiches a thin film of the middle electrolyte （2） against the membrane. When ammonia gas-sensing electrode is immersed in alkaline determinant solution contained NaOH, ammonium

12、 salt in solution converts to ammonia, which diffuses into the middle electrolyte （2） through the membrane （1） and undergoes the following reaction:NH3+H2ONH4+OH-The concentration of NH4 present originally in the middle electrolyte is probingly more than the quantity of NH4 formed by the above react

13、ion, therefore its change may be negligible. But the pH of middle electrolyte in the thin film rises due to the OH- formed. The activity of Cl- in middle electrolyte is constant. The potential of Ag/AgCl reference electrode therefore is constant. When the temperature is constant, thus the potential

14、of the electrode couple consisted of pH glass electrode and Ag/AgCl electrode varies only with the change of pH in middle electrolyte. That is to say, the potentials measured would be similarly a Nernst relation with concentrations of ammonia in external test solution.2.3 RTE=Const - log（NH3）FThe bl

15、ank potential is about +80mV.The linear range （when measuring ammonia） is 110-5-110-1mol/l. Its limit of detection is about 510-6mol/l. It is suitable for room temperature not above 40.This electrode consists of outer tube （gas-permeable membrane has been fitted on but middle electrolyte has not bee

16、n filled yet） and internal electrode. Additionally the gas-permeable membrane is included.1. Installation and preservationThe installation of the electrode is as follows:（1） Twist off the hold-down nut （13） first, take out the internal electrode and immerse in solution of 0.1mol/l NH4Cl for more tha

17、n 1 hour.（2） Prepare the middle electrolyte （0.1mol/l NH4Cl）. Another component middle electrolyte may be used also according to the special conditions of application. But it requires that the activity of chloride ion must be constant, the concentration of ammonium ion is more than that of NH4+ form

18、ed during measurement, the buffering capacity of pH must be as small as possible, the total ionic strength of middle electrolyte and that of external solution to be measured should be nearly the same. But it is worthy of note that the pH glass electrode responses more slowly in concentrated solution

19、 of alkali metal salts.（3） Fit the gas-permeable membrane on the electrode. If the electrode is first time to use, the originally fitted gas-permeable membrane may be used. If the membrane shows break or useless after using of long duration, twist off the hold-down nut （13） first, take out the glass

20、 electrode, then twist off the thread situated at the washer （8） and linked up the two outer tubes of upper part （10） and lower part （7）, take out the internal sleeve （6） and the washer （4） simultaneously from the lower outer tube （7）, discard the gas-permeable membrane （1） fitted originally, rinse

21、all the parts, absorb to dry with filter paper, put a new membrane on the upper orifice of outer tube （7） to the extent of making them to be lain in a same center line, then put on the washer （4） to align the orifice of outer tube （7）, let the internal tube （6） to align the washer （4） and to be pres

22、sed into outer tube （7）. Twist back the thread situated at the washer （8） tightly. The smooth surface of membrane should be fitted toward out and the reverse side toward inside and touched the sensitive membrane of glass electrode, When the gas-permeable membrane has been fitted on the electrode, fi

23、ll pure water or middle electrolyte in it, observe whether it has a water leak or not, if it leaks, replace it by a new membrane.（4） Filling of middle electrolyte and fitting of sensitive electrode. Rinse the inner parts of electrode sleeve （in which the membrane has been fitted already） with middle

24、 electrolyte, the flat-head glass electrode and the Ag/AgCl electrode can be inserted into the electrode sleeve during rinsing. Then the middle electrolyte of 2ml is filled in the electrode tube, insert the glass electrode in it according to the original way. Lock the electrode tightly by means of h

25、old-down nut and check that the sensitive membrane of glass electrode must keep close to the gas-permeable membrane.（5） After installation, immerse the electrode in a solution of 0.1mol/l NH4Cl for storing and using. If another middle electrolyte of different component has been used, a solution of N

26、H4Cl whose ionic strength is equal to that of the middle electrolyte must be used for storing. The concentration and dry of the solution used for storing should be prevented. The effect of storing solution is to prevent the change of composition in middle electrolyte film caused by the dilution or c

27、oncentration because of the change in osmotic pressure. Soaking the electrode in storing solution before using, good repeatability in potential measurement would be obtained. When not in use for long time, it is suitable to take out the electrode and keep dry for storing.2. Preparation of calibratio

28、n graphUse the ammonium chloride dried at 105 to prepare standard solutions. A more dilute standard solution should be prepared near the time of use and with fresh deionized water.Take a series of standards of concentration 0.1, 1.0, 10, 100 mg/l in a beaker of 50ml respectively （or take a series st

29、andards over the appropriate concentration range needed in practical analysis） Place the beaker on a magnetic stirrer, add a stirring bar, immerse the ammonia electrode （note that no gas bubbles adhered on the membrane）, add 1ml of 10mol/l NaOH accurately, take potential readings after equilibration

30、. The plug of electrode should be kept clean and dry so as to ensure to have good insulation, otherwise the measuring result would be influenced severely. The electrode should be rinsed with pure water after measuring a solution, if necessary, immerse the electrode in pure water, observe （under magn

31、etic stirring） the values of potential to restore to the blank potential or to that value almost below the deserved potential of the lowest standard solution in series of standards. It is unnecessary to turn off the reading switch during changing solutions and rinsing.Electrode installed every time maybe ins