原子吸收分光光度計主要用於分析微量到痕量級的無機元素,可以完成定性和定量分析,具有檢出限低、選擇性好、精密度高、抗(kang)幹(gan)擾(rao)能(neng)力(li)強(qiang)等(deng)特(te)點(dian)。空(kong)心(xin)陰(yin)極(ji)燈(deng)提(ti)供(gong)光(guang)源(yuan),待(dai)測(ce)元(yuan)素(su)通(tong)過(guo)原(yuan)子(zi)化(hua)後(hou)對(dui)特(te)征(zheng)波(bo)長(chang)輻(fu)射(she)產(chan)生(sheng)吸(xi)收(shou),通(tong)過(guo)測(ce)定(ding)此(ci)吸(xi)收(shou)的(de)大(da)小(xiao)來(lai)計(ji)算(suan)出(chu)待(dai)測(ce)元(yuan)素(su)的(de)含(han)量(liang)。在(zai)分(fen)析(xi)過(guo)程(cheng)中(zhong)影(ying)響(xiang)測(ce)量(liang)的(de)可(ke)變(bian)因(yin)素(su)多(duo),各(ge)種(zhong)測(ce)量(liang)條(tiao)件(jian)不(bu)易(yi)重(zhong)複(fu),對(dui)測(ce)定(ding)的(de)靈(ling)敏(min)度(du)和(he)準(zhun)確(que)度(du)影(ying)響(xiang)較(jiao)大(da),因(yin)此(ci),如(ru)何(he)選(xuan)擇(ze)和(he)調(tiao)整(zheng)儀(yi)器(qi)的(de)最(zui)佳(jia)工(gong)作(zuo)狀(zhuang)態(tai)非(fei)常(chang)的(de)重(zhong)要(yao)。
如何選擇儀器的最佳工作狀態
1、環境條件的選擇
具體分析試樣時,試樣溶液的溫度、試shi樣yang溶rong液ye的de放fang置zhi位wei置zhi及ji液ye麵mian高gao低di都dou對dui提ti升sheng速su率lv有you很hen大da影ying響xiang。溶rong液ye的de粘zhan度du隨sui液ye體ti的de溫wen度du而er變bian化hua。因yin而er液ye溫wen直zhi接jie影ying響xiang溶rong液ye的de提ti升sheng速su率lv。故gu必bi須xu保bao持chi標biao準zhun溶rong液ye與yu被bei測ce液ye具ju有you相xiang同tong的de溫wen度du,要yao注zhu意yi使shi溶rong液ye溫wen度du與yu環huan境jing溫wen度du保bao持chi一yi致zhi。在zai安an放fang原yuan子zi吸xi收shou儀yi的de房fang間jian,特te剮gua要yao注zhu意yi防fang塵chen,香xiang煙yan的de煙yan霧wu、棉(mian)毛(mao)等(deng)有(you)機(ji)粉(fen)塵(chen)在(zai)火(huo)焰(yan)中(zhong)燃(ran)燒(shao),會(hui)出(chu)現(xian)紅(hong)火(huo)星(xing),使(shi)噪(zao)音(yin)升(sheng)高(gao),重(zhong)現(xian)性(xing)變(bian)差(cha)。安(an)放(fang)儀(yi)器(qi)的(de)房(fang)問(wen)禁(jin)止(zhi)吸(xi)煙(yan)。同(tong)樣(yang)要(yao)注(zhu)意(yi)氣(qi)體(ti)鋼(gang)瓶(ping)的(de)安(an)放(fang)地(di)點(dian)。鋼(gang)瓶(ping)不(bu)能(neng)放(fang)在(zai)露(lu)天(tian),因(yin)為(wei)鋼(gang)瓶(ping)的(de)氣(qi)體(ti)壓(ya)力(li)會(hui)隨(sui)溫(wen)度(du)而(er)發(fa)生(sheng)變(bian)化(hua),影(ying)響(xiang)測(ce)定(ding)結(jie)果(guo)。最(zui)好(hao)是(shi)安(an)放(fang)在(zai)儀(yi)器(qi)隔(ge)壁(bi)的(de)房(fang)間(jian)內(nei)。
2、共振線、波長的選擇
meizhongyuansudefenxixianyouhenduotiao,diyigongzhenxianlingminduzuigao,tongchangbeiyonglaizuoweifenxixian,danshiyeyaokaolvcedingzhongganraoyinsudeyingxiang,yibaozhengwendingxing。liruceNa時常用589.0nm波長作為分析線,但Na濃度較高時可采用330.0nmbochangjinxingceding。youyukongxinyinjidengdianliudaxiaodebianhuahuodanseqichuandongjigoubujingmidengyinqidewucha,zaishijifenxishishezhideceliangbochangdeshizhikenenghelilunzhibuwanquanyizhi。yincishiyongyiqishiyingdingqixiaozhengxishoubochangdeweizhi。
3、空心陰極燈
3.1預熱時間
weishiguangyuanwending,bixuduidengjinxingyure,shidengneiyuanzizhengqidefenbujihouduhengding,zheyangcaihuishidengneiyuanzizhengqichanshengdefushehezixishouwending。zixishoushizhiyouyuyinjineibuwendugaoyuwaibu,yinjiwaibudeyuanzizhengqihuixishouyidingdefushe,zaochengcedinglingmindujiangdi。kongxinyinjidengzaishiyongqian,ruozai1/3工作電流的情況下預熱0.5~1.0h,並(bing)定(ding)期(qi)活(huo)化(hua),其(qi)工(gong)作(zuo)壽(shou)命(ming)可(ke)達(da)上(shang)千(qian)小(xiao)時(shi)。更(geng)換(huan)空(kong)心(xin)陰(yin)極(ji)燈(deng)時(shi),要(yao)小(xiao)心(xin)不(bu)能(neng)把(ba)指(zhi)紋(wen)印(yin)在(zai)燈(deng)宙(zhou)上(shang)。因(yin)為(wei)燈(deng)宙(zhou)是(shi)熱(re)的(de),手(shou)上(shang)的(de)油(you)汙(wu)熔(rong)化(hua),模(mo)糊(hu)了(le)燈(deng)宙(zhou),導(dao)致(zhi)光(guang)強(qiang)度(du)改(gai)變(bian)引(yin)起(qi)信(xin)號(hao)漂(piao)移(yi),帶(dai)入(ru)誤(wu)差(cha)。
3.2工作電流
huoyanyuanzixishoufenguangguangdujishiyongguangyuandadoushikongxinyinjideng,kongxinyinjidengdecaozuocanshuzhiyouyigedengdianliu。dengdianliudedaxiaojieyingxiangdengfangdiandewendingxingheruixianguangdeshuchuqiangdu,jidengdefusheqiangdu。zaiyidingdefanweineizengdadengdianliukeyitigaofusheqiangdu,yizengqiangcedinglingmindu。dandengdianliuguodahuijiakuaidengneiduoxingqitidexiaohaoersuoduandengdeshiyongshouming,bingzaochengfangdianbuzhengchang,shidengfusheqiangduwendingxingjiangdi。erruguodengdianliuguodi,touguoguangjiuhuitairuo,xutigaoguangdianbeizengguanlingmindudezengyi,cishihuizengjiazaoshengerzaochengxinzaobiyanzhongxiajiang。zaishijigongzuozhong,yaogenjubeiceyuansuhanlianggaodilaitiaozhengdengdianliudedaxiao,hanliangjiaogaoshishiyongjiaodadengdianliu,hanliangjiaodishiyibaozhengwendingxingweiqiantijiangdidengdianliu,congerquebaowendingxinghelingmindu。
4、火焰燃燒器
4.1試液提升量
試液提升量較小時,雖然霧化效率高,但絕對吸入量低,測定靈敏度低;若ruo提ti升sheng量liang太tai大da,則ze霧wu化hua效xiao率lv降jiang低di,大da量liang試shi液ye成cheng為wei廢fei液ye排pai出chu,靈ling敏min度du也ye會hui受shou到dao影ying響xiang。因yin此ci,要yao選xuan擇ze合he適shi的de提ti升sheng量liang才cai能neng保bao證zheng測ce定ding的de靈ling敏min度du。試shi液ye提ti升sheng量liang受shou吸xi液ye毛mao細xi管guan的de內nei徑jing與yu長chang度du、通入壓縮空氣的壓強、試液的黏度等因素影響,遵循波斯裏(Poisuue)公式:V=式中:V―試液提升量,cm3/s;r一毛細管內徑,cm;P一壓強,Pa;―試液黏度,Pa・s;L―毛細管的長度,cm。當r.P保持恒定,η.L增大,就會降低試液提升量。通常試液提升量選擇 3~6ml/min,霧化效率可達10%。
4.2火焰類型和狀態
選擇合適的火焰不僅能提高測定的靈敏度和穩定性,還可以減少幹擾。對於易電離、易揮發的元素(如堿金屬和部分堿土金屬)及易與硫化合的元素(如Sn、Se)可使用Air-C3H8,火焰等低溫火焰;對難揮發和易生成氧化物的元素(如Al、Si、Ti等)可使用N2O一C2H:火焰或O2一H2火焰等高溫火焰;對其餘絕大多數元素(如Cu、Pb、Zn、Cd、Fe、Mn等)多采用Air-C2H2火焰。火焰按狀態分為貧焰、化學計量焰、富焰。其中化學計量焰是按照化學計量關係計算的燃料和氧化劑比率燃燒的火焰,具有溫度高、幹擾少、穩定、背景低等特點,除堿金屬和易形成難離解氧化物的元素,大多數常見元素常用這種火焰。
4.3燃燒器的位置
為保證測定靈敏度高應使光源發出的銳線光通過火焰中基態原子密度最大的“中間薄層區”。這個區域火焰比較穩定,幹擾少,約位於燃燒器狹縫口上方2―10mm附近。若不需要高靈敏度時,欲測試樣濃度高時,可以轉動燃燒器至適當角度以減少吸收的光程來降低靈敏度。
如何調整儀器的最佳工作狀態
1、空心陰極燈位置的調整
空心陰極燈是原子吸收儀器的光源,調整空心陰極燈的位胃就是為了使燈的位置、ranshaoqijidushuzhuangzhichengyitiaozhixian,cedingshi,lingminduhezhunquedugenggao。yinci,tiaozhengdengweizhijiranshaoqidexianxingguanxishitiaozhengyiqizuijiazhuangtaideguanjianhuanjie。zaitiaozhengdengweizhishi,dengdianliubuyaokaidezuida,meigeyinjidengdouyouyidingdeshouming,zhiyaobaochifaguangwendingjike。ruguoshiyongshijianguochang,zeyaojiadadengdianliu。zai“能量”檔.正反向旋轉燈調節鈕至能最顯示最大為止。
2、燃燒器的調整
每次測定都會使燃燒器的位置發生移動,每次測定前都必須進行燃燒器位置的調整。以縫隙燃燒器為例,川直徑1mm的改錐垂直立於燃燒器中問部位.能量顯示為“0”,如果不為“0”則調整燃燒器位置旋鈕使之為“0”。平行移動改錐至縫隙的一邊,能量顯示≤30%,如果>30%,則輕輕旋轉燃燒器使之≤30%。同理,平行移動改錐至縫隙的另一邊,調整燃燒器的位置使之≤30%。反複檢查幾次。
3、霧化器的調整
在(zai)火(huo)焰(yan)原(yuan)予(yu)吸(xi)收(shou)分(fen)光(guang)光(guang)度(du)法(fa)測(ce)定(ding)中(zhong),霧(wu)化(hua)器(qi)的(de)霧(wu)化(hua)效(xiao)果(guo)調(tiao)整(zheng)好(hao)壞(huai)直(zhi)接(jie)影(ying)響(xiang)霧(wu)化(hua)效(xiao)果(guo),影(ying)響(xiang)到(dao)測(ce)定(ding)結(jie)果(guo)的(de)準(zhun)確(que)性(xing)。扭(niu)開(kai)霧(wu)化(hua)器(qi),打(da)開(kai)助(zhu)燃(ran)氣(qi)開(kai)關(guan).關(guan)閉(bi)燃(ran)氣(qi)氣(qi)源(yuan),把(ba)進(jin)樣(yang)管(guan)放(fang)在(zai)空(kong)白(bai)液(ye)中(zhong),觀(guan)察(cha)霧(wu)化(hua)器(qi)噴(pen)霧(wu)的(de)效(xiao)果(guo)和(he)形(xing)狀(zhuang),旋(xuan)轉(zhuan)霧(wu)化(hua)器(qi)使(shi)空(kong)白(bai)液(ye)通(tong)過(guo)霧(wu)化(hua)器(qi)噴(pen)成(cheng)的(de)霧(wu)狀(zhuang)為(wei)梨(li)形(xing)。形(xing)成(cheng)的(de)水(shui)滴(di)越(yue)少(shao)霧(wu)化(hua)效(xiao)果(guo)越(yue)好(hao)。
4、火焰的調整
zaiyuanzixishoufenguangguangdufacedingzhong,huoyantiaozhengderuhezhijieyingxiangdaocedingjieguodexianxingguanxi。zhehuojixian,zhehuowenduheranshaosudushihuoyanderanshaotexing。zaishijishiyongzhong,huoyanderanshaosudushisanyaosuzhongzuizhongyaodeyinsu,tazhijieyingxiangzhehuoyandeanquanshiyonghewendingderanshao。qiliusuduqujueyugongqiyali、燃(ran)燒(shao)器(qi)的(de)結(jie)構(gou)形(xing)狀(zhuang),對(dui)於(yu)常(chang)用(yong)縫(feng)式(shi)燃(ran)燒(shao)器(qi),在(zai)給(gei)足(zu)的(de)供(gong)氣(qi)壓(ya)力(li)下(xia),氣(qi)流(liu)速(su)度(du)則(ze)取(qu)決(jue)於(yu)燃(ran)燒(shao)器(qi)的(de)開(kai)口(kou)麵(mian)積(ji),縫(feng)寬(kuan)麵(mian)長(chang),則(ze)氣(qi)流(liu)速(su)度(du)小(xiao),反(fan)之(zhi)則(ze)大(da)。
結語
在原子吸收分光光度法分析過程中可以深深的體會到:使儀器達到最佳的工作狀態是保證測定結果的準確關鍵。所以必須要重視儀器最佳的工作狀態的選擇與調整。
手機版








