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、kangganraonengliqiangdengtedian。kongxinyinjidengtigongguangyuan,daiceyuansutongguoyuanzihuahouduitezhengbochangfushechanshengxishou,tongguocedingcixishoudedaxiaolaijisuanchudaiceyuansudehanliang。zaifenxiguochengzhongyingxiangceliangdekebianyinsuduo,gezhongceliangtiaojianbuyizhongfu,duicedingdelingminduhezhunqueduyingxiangjiaoda,yinci,ruhexuanzehetiaozhengyiqidezuijiagongzuozhuangtaifeichangdezhongyao。
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別bie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
每(mei)種(zhong)元(yuan)素(su)的(de)分(fen)析(xi)線(xian)有(you)很(hen)多(duo)條(tiao),第(di)一(yi)共(gong)振(zhen)線(xian)靈(ling)敏(min)度(du)最(zui)高(gao),通(tong)常(chang)被(bei)用(yong)來(lai)作(zuo)為(wei)分(fen)析(xi)線(xian),但(dan)是(shi)也(ye)要(yao)考(kao)慮(lv)測(ce)定(ding)中(zhong)幹(gan)擾(rao)因(yin)素(su)的(de)影(ying)響(xiang),以(yi)保(bao)證(zheng)穩(wen)定(ding)性(xing)。例(li)如(ru)測(ce)Na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
為wei使shi光guang源yuan穩wen定ding,必bi須xu對dui燈deng進jin行xing預yu熱re,使shi燈deng內nei原yuan子zi蒸zheng氣qi的de分fen布bu及ji厚hou度du恒heng定ding,這zhe樣yang才cai會hui使shi燈deng內nei原yuan子zi蒸zheng氣qi產chan生sheng的de輻fu射she和he自zi吸xi收shou穩wen定ding。自zi吸xi收shou是shi指zhi由you於yu陰yin極ji內nei部bu溫wen度du高gao於yu外wai部bu,陰yin極ji外wai部bu的de原yuan子zi蒸zheng氣qi會hui吸xi收shou一yi定ding的de輻fu射she,造zao成cheng測ce定ding靈ling敏min度du降jiang低di。空kong心xin陰yin極ji燈deng在zai使shi用yong前qian,若ruo在zai1/3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
火huo焰yan原yuan子zi吸xi收shou分fen光guang光guang度du計ji使shi用yong光guang源yuan大da都dou是shi空kong心xin陰yin極ji燈deng,空kong心xin陰yin極ji燈deng的de操cao作zuo參can數shu隻zhi有you一yi個ge燈deng電dian流liu。燈deng電dian流liu的de大da小xiao接jie影ying響xiang燈deng放fang電dian的de穩wen定ding性xing和he銳rui線xian光guang的de輸shu出chu強qiang度du,即ji燈deng的de輻fu射she強qiang度du。在zai一yi定ding的de範fan圍wei內nei增zeng大da燈deng電dian流liu可ke以yi提ti高gao輻fu射she強qiang度du,以yi增zeng強qiang測ce定ding靈ling敏min度du。但dan燈deng電dian流liu過guo大da會hui加jia快kuai燈deng內nei惰duo性xing氣qi體ti的de消xiao耗hao而er縮suo短duan燈deng的de使shi用yong壽shou命ming,並bing造zao成cheng放fang電dian不bu正zheng常chang,使shi燈deng輻fu射she強qiang度du穩wen定ding性xing降jiang低di。而er如ru果guo燈deng電dian流liu過guo低di,透tou過guo光guang就jiu會hui太tai弱ruo,需xu提ti高gao光guang電dian倍bei增zeng管guan靈ling敏min度du的de增zeng益yi,此ci時shi會hui增zeng加jia噪zao聲sheng而er造zao成cheng信xin噪zao比bi嚴yan重zhong下xia降jiang。在zai實shi際ji工gong作zuo中zhong,要yao根gen據ju被bei測ce元yuan素su含han量liang高gao低di來lai調tiao整zheng燈deng電dian流liu的de大da小xiao,含han量liang較jiao高gao時shi使shi用yong較jiao大da燈deng電dian流liu,含han量liang較jiao低di時shi以yi保bao證zheng穩wen定ding性xing為wei前qian提ti降jiang低di燈deng電dian流liu,從cong而er確que保bao穩wen定ding性xing和he靈ling敏min度du。
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;ruotishengliangtaida,zewuhuaxiaolvjiangdi,daliangshiyechengweifeiyepaichu,lingminduyehuishoudaoyingxiang。yinci,yaoxuanzeheshidetishengliangcainengbaozhengcedingdelingmindu。shiyetishengliangshouxiyemaoxiguandeneijingyuchangdu、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).guanbiranqiqiyuan,bajinyangguanfangzaikongbaiyezhong,guanchawuhuaqipenwudexiaoguohexingzhuang,xuanzhuanwuhuaqishikongbaiyetongguowuhuaqipenchengdewuzhuangweilixing。xingchengdeshuidiyueshaowuhuaxiaoguoyuehao。
4、火焰的調整
zaiyuanzixishoufenguangguangdufacedingzhong,huoyantiaozhengderuhezhijieyingxiangdaocedingjieguodexianxingguanxi。zhehuojixian,zhehuowenduheranshaosudushihuoyanderanshaotexing。zaishijishiyongzhong,huoyanderanshaosudushisanyaosuzhongzuizhongyaodeyinsu,tazhijieyingxiangzhehuoyandeanquanshiyonghewendingderanshao。qiliusuduqujueyugongqiyali、ranshaoqidejiegouxingzhuang,duiyuchangyongfengshiranshaoqi,zaigeizudegongqiyalixia,qiliusuduzequjueyuranshaoqidekaikoumianji,fengkuanmianchang,zeqiliusuduxiao,fanzhizeda。
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。
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