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:caiyongmafulugaowenhuihuachuliyangpin,yixierongyihuifadeyuansucedinghuishoulvpiandideyuanyinzhengshiyouyugaowenshidaiceyuansuhuifasunshiyinqide。yinci,tongguocedinghuishoulvdejieguo,kezaiyidingchengdushangzhengmingfangfadezhunquexing。
加標量的水平及其準確性的影響
在(zai)化(hua)學(xue)分(fen)析(xi)中(zhong),由(you)於(yu)待(dai)測(ce)物(wu)質(zhi)都(dou)是(shi)在(zai)一(yi)定(ding)的(de)濃(nong)度(du)範(fan)圍(wei)內(nei)才(cai)具(ju)有(you)某(mou)個(ge)特(te)定(ding)的(de)準(zhun)確(que)度(du),超(chao)出(chu)該(gai)範(fan)圍(wei),可(ke)能(neng)會(hui)產(chan)生(sheng)較(jiao)大(da)的(de)誤(wu)差(cha)。在(zai)做(zuo)加(jia)標(biao)回(hui)收(shou)時(shi),當(dang)樣(yang)品(pin)中(zhong)待(dai)測(ce)物(wu)含(han)量(liang)較(jiao)低(di)時(shi)。加(jia)入(ru)標(biao)準(zhun)物(wu)質(zhi)太(tai)少(shao),測(ce)得(de)回(hui)收(shou)率(lv)誤(wu)差(cha)較(jiao)大(da);jiarubiaozhunwuzhitaiduo,zehuigaibiandaicewuzhizaijiabiaoyangpinheyangpinzhongdecedingbeijing,yekenenghuichanshengjiaodadewucha。yincizaijinxingjiabiaohuishoushi,jiabiaoliangdeshuipingyaoshidang,taigaohuotaididoubuhuidedaoyuqidexiaoguo,tongchangyingzhuyiyixialiangdian。
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:zaicaiyongnongsuanxiaojieyangpinshi。guoduojiarushuirongye。shisuannongdutaidi,kenengyingxiangyangpinxiaoguo。dangjiarubiaozhunwuzhishiyoujirongjishi,jiabiaoliangguoduo,zehuizaochengrongjihebiaozhunwuzhinanyizaishuizhongrongjie,congeryinrongjieduwentizaochengduijiabiaohuishoulvdeyingxiang。
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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