Abstract
本研究以二階萃取前濃縮法配合微分脈衝陽極剝除伏安法測定海水中的微 量重金屬元素闡闡闡鋅、鎘、鉛和銅。二階萃取前濃縮法包括第一階段利 用自行製備的高純度半胱胺酸乙酯雙聚體闡騖CD (L,L- ethylenedicysteine diethylester) 從海水中萃取微量金屬到氯仿中， 然後第二階段中以Hg溶液進行反萃。在萃取過程中，將海水pH調整於4.0 ∼4.5，以達高萃取效率。在反萃過程中，Hg2+溶液之pH值宜採用pH3∼4 ，除了可達高反萃效率外，亦可配合下一步驟重金屬之電化學分析。萃取 與反萃取時加大兩相體積比可提高濃縮倍數。於反萃過程中使用過量Hg2+ 置換有機相中螯合之金屬，是以待電化學分析之溶液，除了含待測微量金 屬離子外尚有過剩之 Hg2+，此Hg2+可作為現場式(in situ) 光滑電極 (glassy carbon electrode)上產生汞膜的來源，頗利於微分脈衝陽極剝 除伏安法分析。按本研究所採用之分析步驟取海水200ml 為試劑，經 ECD 萃取，以10ml 300ppm Hg2+反萃，最後以微分脈衝陽極剝除伏安法測定金 屬離子，對天然海水中之分析做為四種金屬離子之偵測極限分別為鋅 0.03ppb、鎘 0.08ppb、鉛 0.03ppb、銅 0.05ppb。在核子醫學界，Tc- ECD 是一良好的腦造影劑；若將 ECD應用至分析化學界則是良好的萃取劑 ，由此顯現出 ECD深具有的廣用性及開發性。當海域環境日漸地受到關切 ，我們的目標即是朝著研發實用，可行又準確的分析方法，參與海域的環 保，期能有所貢獻 A two-step preconcentration procedure is proposed to be used in conjuction with differential pulse anodic stripping voltammetry for the determination of tracer metals in seawater. The two-step preconcentration involves extraction of trace metals from seawater with L,L-ethyl- enedicysteine diethylester (ECD) into chloroform followed by backextraction with a Hg(Ⅱ) solution. The extraction could concentration the trace metals by forming a chelate with ECD with a high enrichment factor obtained with the large phase volume ratio. The aqueous solution containing simply the enriched metals and some of the nonreacted Hg (Ⅱ) was taken for differential pulse anodic stripping voltammetry (DPASV) using a glassy carbon electrode.Anodic stripping voltammetry of the metals such as Zn,Cd,Pb and Cu were done directly in the backextraction solution, i.e., Hg(Ⅱ). It should be worthwhile to note that the Hg(Ⅱ) solution used as the backextraction agent does not cause any interference in the anodic stripping voltammetry. Be- sides,the Hg(Ⅱ) can be used in situ as the source of mer- cury film to be coated on the glassy carbon electrode,ren- dering it as effective working electrode for DPASV.