幾種常用樣品前處理方法在食品重金屬檢驗中的應用
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濕消化法
濕shi消xiao化hua法fa是shi在zai適shi量liang的de食shi品pin樣yang品pin中zhong,加jia入ru氧yang化hua性xing強qiang酸suan,加jia熱re破po壞huai有you機ji物wu,使shi待dai測ce的de無wu機ji成cheng分fen釋shi放fang出chu來lai,形xing成cheng不bu揮hui發fa的de無wu機ji化hua合he物wu,以yi便bian進jin行xing分fen析xi測ce定ding。
濕法消化是目前應用比較廣泛的一種食品樣品前處理方法,該方法實用性強,幾乎所有的食品都可以用該方法消化。
下麵介紹下濕法消解的優勢:首先、前處理所用的試劑即酸都可以找到高純度的,同時基體成分都比較簡單(偶爾也會產生部分硫酸鹽);其次、在zai實shi驗yan過guo程cheng中zhong,隻zhi要yao控kong製zhi好hao消xiao化hua溫wen度du,大da部bu分fen元yuan素su一yi般ban很hen少shao或huo幾ji乎hu沒mei有you損sun失shi。例li如ru,在zai測ce定ding醬jiang油you中zhong的de砷shen含han量liang時shi采cai用yong濕shi法fa消xiao化hua加jia入ru了le硝xiao酸suan高gao氯lv酸suan混hun合he酸suan和he硫liu酸suan,加jia標biao回hui收shou率lv為wei95%以上。即便像“汞”等極易揮發的元素,隻要正確掌握消化溫度,也不會有損失。
但是濕消化法也有一定的缺陷:
首先,由於該反應是氧化反應,樣品氧化時間較長,需要一個小時左右的時間(隨樣品的成分而定),且實驗過程中一次不能消化超過10個樣品,因此方法的勞動強度比較大。
其次,樣品消化時常使用的試劑硝酸、高氯酸、guoyanghuaqing,liusuandoushijuyoufushixingqiebijiaoweixiande。zaiyongxiaosuanhegaolvsuanshichanshengdesuanwuheyan,duitongfengchudefushixingyehenda。tebiexuyaozhuyideshiyonggaolvsuanxiaojieyangpinshi,yingyangezunshoucaozuoguicheng,shaobeizhongyetibunengshaogan,bingqieyaobaozhengwendudadao200攝氏度時隻有少量的有機成分存在,否則高氯酸的氧化電位在此溫度下會迅速升高,會導致劇烈的爆炸!yincijianyi,zaishiyonggaolvsuanshi,zuihaoxianyongxiaosuanyanghuabufendeyoujiwu,huozheshixianjiaruxiaosuanyugaolvsuandehunheyejinpaoyiye,tongshishiyanyaozaitongfengchuneijinxing。xiaohuayebunengzhenggan,yifangbufenyuansuruxi、鉛的損失。
haiyou,youyuyanghuafanyingguochengzhongjiarulenongsuan,zhexiesuankenenghuiduiyiqichanshengsunhaijineryingxiangshiyanjieguo,yincixiaojiejieshuhouxuyaopaisuan,liru,yongyuanziyingguangcedingzongshen,cedingshixiaosuandecunzaihuifangaidechansheng,duicedingyouganrao,xiaojiewanquanhouyingjinkenengdejiarequchuxiaosuan。guobiaoshiyanzhongcaiyongxiaosuan-硫酸消解樣品,由於硫酸的沸點比硝酸要高,所以最後消化液裏基本上沒有硝酸。但是需要注意的是,采用硝酸-liusuanxiaojieyangpinshiyinbimianfashengtanhua,xiaojieguochengfashengtanhuashihuishishenyanzhongsunshi,suoyizaixiaojieguochengzhongzhuyiruoxiaohuayesezebianshenyingshidangbujiaxiaosuan,zhidezhuyideshizaibiaozhunquxianyeyaobaozhengheyangpinxiaojieyezhongxiangtongdesuannongdujiyaojitipipei。
某些特殊食品濕消解時注意事項:
含油脂成分較高的食品,如植物油、桃(tao)酥(su)等(deng),在(zai)加(jia)入(ru)混(hun)合(he)酸(suan)後(hou),由(you)於(yu)樣(yang)品(pin)浮(fu)在(zai)混(hun)酸(suan)表(biao)麵(mian)上(shang),容(rong)易(yi)形(xing)成(cheng)完(wan)整(zheng)的(de)膜(mo),加(jia)熱(re)時(shi)液(ye)麵(mian)上(shang)有(you)劇(ju)烈(lie)的(de)反(fan)應(ying),容(rong)易(yi)造(zao)成(cheng)爆(bao)沸(fei)或(huo)飛(fei)濺(jian),因(yin)此(ci)建(jian)議(yi)樣(yang)品(pin)稱(cheng)樣(yang)量(liang)不(bu)高(gao)於(yu)1g(植物油最好為0.1-0.2g),同時要在消解過程中隨時補加硝酸,一般來講硝酸高氯酸混合液加入15ml,放置過夜讓其緩慢氧化,次日消化中途還需要補加混合酸10ml左右。
酒類樣品如葡萄酒、果酒,因其含有大量的乙醇,在加混合酸消化之前一定要加熱蒸發掉乙醇(注意不能幹涸),daiyichunhuifawanbihou,zaijiarusuanxiaohua。wozengjingzaixiaohuaputaojiuyangpinshi,weipaiyichunzhijiejiarulehunhesuan,jieguoguolejifenzhonghou,fanyingfeichangjulie,chanshengdaliangqipaotongshiyangpinwaiyi,daozhishiyanshibai。
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