PH電極的原理和使用維護注(zhu)意事項
核(he)心提示(shi)：
PH電(dian)極(ji)(ji)又稱PH探(tan)頭(tou)，是(shi)PH計上與被測物(wu)質接觸(chu)的(de)部分，用來測電(dian)極(ji)(ji)電(dian)位的(de)裝置(zhi)。
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位分析法所用(yong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極被稱(cheng)(cheng)為原電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)。原電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)是(shi)一個(ge)系統(tong)，它(ta)的(de)(de)作用(yong)是(shi)使(shi)化學反應能量轉成為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能。此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)被稱(cheng)(cheng)為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動勢（EMF）。此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動勢（EMF）由二個(ge)半電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)構成。其(qi)中一個(ge)半電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)稱(cheng)(cheng)作測量電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極，它(ta)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位與特定(ding)的(de)(de)離子活度有(you)關(guan)；另一個(ge)半電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)為參比(bi)半電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)，通常稱(cheng)(cheng)作參比(bi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極，它(ta)一般是(shi)與測量溶液(ye)相通，并(bing)且與測量儀表相連。最熟悉也是(shi)最常用(yong)的(de)(de)PH指(zhi)示(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極是(shi)玻(bo)璃電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極。貝爾公司(si)T225電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極適用(yong)于(yu)醫(yi)藥紙(zhi)漿(jiang)造(zao)紙(zhi)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)鍍、生物制(zhi)藥、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)廠等行業的(de)(de)純(chun)水，高(gao)純(chun)水的(de)(de)測量。它(ta)是(shi)一支端(duan)部吹(chui)制(zhi)上對于(yu)pH敏(min)感的(de)(de)玻(bo)璃膜的(de)(de)玻(bo)璃管(guan)。管(guan)內充填有(you)含飽和AgCl的(de)(de)3 mol/l kcl緩(huan)沖(chong)溶液(ye)，其(qi)pH值為7。存在于(yu)玻(bo)璃膜二面的(de)(de)反映PH值的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位差用(yong)Ag/AgCl傳導(dao)系統(tong)。
pH電極使用維(wei)護(hu)的注意事項：
1．電(dian)極在測量前必須用已知pH值的標(biao)準(zhun)緩(huan)沖溶液進行標(biao)定（至少2點）。
2．在(zai)每次標定、測量(liang)后進行下一次操(cao)作前，應該用蒸餾水或(huo)去離子(zi)水分清洗電極，再用被測液清洗一次電極。
3．取下電極護套(tao)時(shi)，應避免電極的敏感玻璃泡與硬物(wu)接觸，因為(wei)任何破損或(huo)擦毛都使電極失效(xiao)。
4．測量結束，及時將(jiang)電(dian)極(ji)保護套(tao)套(tao)上，電(dian)極(ji)套(tao)內(nei)應放少量飽和(he)KCL液,以保持電(dian)極(ji)球(qiu)泡(pao)的(de)濕潤，切(qie)忌浸泡(pao)在蒸餾水中。
5．復(fu)合電極的外參比補充液(ye)為(wei)3mol／L氯化鉀溶液(ye)，補充液(ye)可以從電極上端小孔加入，復(fu)合電極不(bu)使用時(shi)，蓋上橡皮塞，防止(zhi)補充液(ye)干涸，在線pH電極1般是凝膠的，所以不(bu)需要添(tian)加電解液(ye)。
6．電極的引出端(duan)必須保持(chi)清潔干燥，絕對(dui)防止(zhi)輸出兩端(duan)短路(lu)，否則將導致測(ce)量(liang)失準或失效。
7．電極應與(yu)輸入(ru)阻(zu)抗較高的pH計≥3×1011Ω 配套，以使(shi)其(qi)保(bao)持良好的特性。
8．電極應避免長(chang)期浸在蒸餾水、蛋(dan)白質溶液(ye)和(he)酸性氟化物溶液(ye)中。
9．電極避免與有(you)機硅油接觸。
10．電極經長(chang)期使(shi)用(yong)后，如發現斜率略有降(jiang)低(di)，則(ze)可把(ba)電極下端(duan)浸泡在4%HF氫氟(fu)酸 中（3~5）s， 用(yong)蒸(zheng)餾水洗凈、然后在0.1 mo l／L鹽(yan)酸溶液中浸泡，使(shi)之復(fu)新，最(zui)好更換電極。
11．被(bei)測溶液(ye)中(zhong)如(ru)含有易污染敏(min)感(gan)球泡或堵塞液(ye)接(jie)界的物質而使電極鈍化，會(hui)出現(xian)斜(xie)率降低，顯示(shi)讀數不準現(xian)象(xiang)。如(ru)發(fa)生該現(xian)象(xiang)，則應根(gen)據污染物質的性質，用適(shi)當溶液(ye)清(qing)洗，使電極復新(xin)。
