分析與條件的影響
理li論lun上shang,任ren何he分fen析xi方fang法fa都dou有you一yi定ding的de誤wu差cha,且qie不bu同tong分fen析xi方fang法fa誤wu差cha存cun在zai較jiao大da的de差cha異yi。在zai化hua學xue分fen析xi中zhong,通tong常chang的de標biao準zhun方fang法fa對dui準zhun確que度du有you一yi定ding的de要yao求qiu,允yun許xu的de誤wu差cha也ye是shi相xiang對dui的de。有you的de檢jian測ce項xiang目mu,由you於yu分fen析xi方fang法fa本ben身shen存cun在zai一yi定ding的de局ju限xian性xing,而er造zao成cheng加jia標biao回hui收shou率lv值zhi偏pian低di或huo偏pian高gao。
如:采cai用yong馬ma弗fu爐lu高gao溫wen灰hui化hua處chu理li樣yang品pin,一yi些xie容rong易yi揮hui發fa的de元yuan素su測ce定ding回hui收shou率lv偏pian低di的de原yuan因yin正zheng是shi由you於yu高gao溫wen使shi待dai測ce元yuan素su揮hui發fa損sun失shi引yin起qi的de。因yin此ci,通tong過guo測ce定ding回hui收shou率lv的de結jie果guo,可ke在zai一yi定ding程cheng度du上shang證zheng明ming方fang法fa的de準zhun確que性xing。
加標量的水平及其準確性的影響
zaihuaxuefenxizhong,youyudaicewuzhidoushizaiyidingdenongdufanweineicaijuyoumougetedingdezhunquedu,chaochugaifanwei,kenenghuichanshengjiaodadewucha。zaizuojiabiaohuishoushi,dangyangpinzhongdaicewuhanliangjiaodishi。jiarubiaozhunwuzhitaishao,cedehuishoulvwuchajiaoda;加(jia)入(ru)標(biao)準(zhun)物(wu)質(zhi)太(tai)多(duo),則(ze)會(hui)改(gai)變(bian)待(dai)測(ce)物(wu)質(zhi)在(zai)加(jia)標(biao)樣(yang)品(pin)和(he)樣(yang)品(pin)中(zhong)的(de)測(ce)定(ding)背(bei)景(jing),也(ye)可(ke)能(neng)會(hui)產(chan)生(sheng)較(jiao)大(da)的(de)誤(wu)差(cha)。因(yin)此(ci)在(zai)進(jin)行(xing)加(jia)標(biao)回(hui)收(shou)時(shi),加(jia)標(biao)量(liang)的(de)水(shui)平(ping)要(yao)適(shi)當(dang),太(tai)高(gao)或(huo)太(tai)低(di)都(dou)不(bu)會(hui)得(de)到(dao)預(yu)期(qi)的(de)效(xiao)果(guo),通(tong)常(chang)應(ying)注(zhu)意(yi)以(yi)下(xia)兩(liang)點(dian)。
一是標準加入的量要明顯高於檢出限,二是要盡量與分析組分的含量一致,但同時考慮又不能超出方法檢測的容許範圍。
例如:zaifenguangguangdufenxizhong,dangyangpinzhongdaicewuhanliangjiaogaoshi,jiarubiaozhunwuzhiguogao,shijiabiaohoucedingzhijiejinfangfadejianchushangxian,zheyangcedejiabiaoyangzhongdaicewudewuchajiaoda,jiabiaohouyinqidenongduzengliangzaifangfacedingshangxiannongduc的0.4~0.6倍之間為宜。
加標體積影響
通(tong)常(chang)情(qing)況(kuang)下(xia),盡(jin)管(guan)因(yin)加(jia)標(biao)而(er)增(zeng)大(da)了(le)試(shi)樣(yang)體(ti)積(ji),樣(yang)品(pin)分(fen)析(xi)過(guo)程(cheng)中(zhong)有(you)蒸(zheng)發(fa)或(huo)消(xiao)解(jie)等(deng)可(ke)使(shi)溶(rong)液(ye)體(ti)積(ji)縮(suo)小(xiao)的(de)操(cao)作(zuo)技(ji)術(shu)時(shi),樣(yang)品(pin)經(jing)處(chu)理(li)後(hou)重(zhong)新(xin)定(ding)容(rong)並(bing)不(bu)會(hui)對(dui)分(fen)析(xi)結(jie)果(guo)產(chan)生(sheng)影(ying)響(xiang)。但(dan)加(jia)標(biao)體(ti)積(ji)過(guo)大(da),容(rong)易(yi)因(yin)加(jia)入(ru)過(guo)多(duo)溶(rong)劑(ji)影(ying)響(xiang)檢(jian)測(ce)結(jie)果(guo)。
如:在(zai)采(cai)用(yong)濃(nong)酸(suan)消(xiao)解(jie)樣(yang)品(pin)時(shi)。過(guo)多(duo)加(jia)入(ru)水(shui)溶(rong)液(ye)。使(shi)酸(suan)濃(nong)度(du)太(tai)低(di),可(ke)能(neng)影(ying)響(xiang)樣(yang)品(pin)效(xiao)果(guo)。當(dang)加(jia)入(ru)標(biao)準(zhun)物(wu)質(zhi)是(shi)有(you)機(ji)溶(rong)劑(ji)時(shi),加(jia)標(biao)量(liang)過(guo)多(duo),則(ze)會(hui)造(zao)成(cheng)溶(rong)劑(ji)和(he)標(biao)準(zhun)物(wu)質(zhi)難(nan)以(yi)在(zai)水(shui)中(zhong)溶(rong)解(jie),從(cong)而(er)因(yin)溶(rong)解(jie)度(du)問(wen)題(ti)造(zao)成(cheng)對(dui)加(jia)標(biao)回(hui)收(shou)率(lv)的(de)影(ying)響(xiang)。
由(you)於(yu)加(jia)標(biao)回(hui)收(shou)率(lv)試(shi)驗(yan)需(xu)要(yao)操(cao)作(zuo)人(ren)員(yuan)經(jing)過(guo)一(yi)係(xi)列(lie)操(cao)作(zuo)步(bu)驟(zhou)完(wan)成(cheng),除(chu)了(le)加(jia)標(biao)的(de)步(bu)驟(zhou)外(wai),其(qi)他(ta)任(ren)何(he)與(yu)樣(yang)品(pin)檢(jian)測(ce)有(you)關(guan)的(de)操(cao)作(zuo)步(bu)驟(zhou)都(dou)可(ke)能(neng)影(ying)響(xiang)加(jia)標(biao)樣(yang)品(pin)和(he)原(yuan)樣(yang)品(pin)中(zhong)待(dai)測(ce)組(zu)分(fen)的(de)結(jie)果(guo),所(suo)以(yi),這(zhe)些(xie)操(cao)作(zuo)人(ren)員(yuan)的(de)水(shui)平(ping)均(jun)直(zhi)接(jie)影(ying)響(xiang)回(hui)收(shou)率(lv)的(de)結(jie)果(guo)。
通常情況下,樣品待測組分本底值(原含量)不能過大。樣品本底值太大,加標量無法與之匹配,回收量的相對誤差就大,回收率偏差即大;反之回收率偏差即小。因此,在低濃度區加標回收率要受樣品中本底值的影響更為明顯。
回hui收shou率lv試shi驗yan的de前qian提ti是shi樣yang品pin足zu夠gou均jun勻yun,即ji樣yang品pin及ji加jia標biao樣yang品pin本ben底di值zhi差cha異yi可ke以yi忽hu略lve。反fan之zhi,如ru果guo樣yang品pin均jun勻yun較jiao差cha,樣yang品pin及ji加jia標biao樣yang品pin本ben底di值zhi差cha異yi較jiao大da,加jia標biao樣yang品pin與yu樣yang品pin中zhong待dai測ce物wu質zhi含han量liang的de差cha值zhi將jiang不bu僅jin僅jin是shi加jia標biao物wu質zhi的de測ce定ding值zhi,即ji為wei加jia標biao回hui收shou試shi驗yan采cai用yong的de兩liang份fen待dai測ce定ding樣yang品pin與yu樣yang品pin中zhong待dai測ce物wu質zhi含han量liang的de差cha值zhi及ji加jia標biao物wu質zhi總zong和he的de測ce定ding值zhi。因yin此ci,如ru加jia標biao樣yang中zhong待dai測ce物wu質zhi本ben底di偏pian高gao,回hui收shou率lv將jiang偏pian高gao,反fan之zhi則ze偏pian低di。樣yang品pin間jian差cha異yi過guo大da,將jiang得de到dao錯cuo誤wu的de回hui收shou率lv結jie果guo。
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