适用于海洋沉积物间隙水中氧、锰(Ⅱ)、铁(Ⅱ)、硫分析的金汞齐微电极

Development of Hg-Au Microelectrode for Measuring O_2,Mn^(2+),Fe^(2+),and S^(2-) in Marine Sediment Pore Water

用电化学方法在金微电极的基础上制成金汞齐微电极。研究了电极预处理方法、电镀以及强极化金汞齐微电极的条件、电极的校正方法以及实际测量电化学参数的选择等。采用三电极体系和方波伏安法,金汞齐微电极(vs.SCE)从-0.10～-1.75V电势范围内可同时测定沉积物间隙水中的溶解氧、Mn2+、Fe2+和S2-等氧化还原物的浓度。实验结果表明金汞齐微电极对溶解氧、Mn2+、Fe2+和S2-的灵敏度和检出限分别为0.16nA/(μmol/L)、6μmol/L,0.35nA/(μmol/L)、3μmol/L,0.22nA/(μmol/L)、5μmol/L和34nA/(μmol/L)、0.03μmol/L。在连续测定15个沉积物样品后,重新校正电极,测量相对误差<3%。

Hg-Au vohammetric microelectrodes were developed by electroplating mercury membrane onto Au microelectrodes. The Au electrode was constructed by sealing one end of a 100 μm diameter gold wire within a glass capillary using epoxy and attaching the other end to a silver wire for electrical contact using conductive epoxy. The silver wire was fastened to the top of the glass tube using epoxy again. The tip of the electrode was ground flat and smooth gradually from coarse to fine grain under a micropolisher. It was then washed with 1 mol/L HNO3 solution and in deionized water under supersonic action. The electrode was electroplated with a layer of mercury within 0.1 mol/L Hg（ NO3 ）2-0.03 mol/L HNO3 electrolyte at a potential of -0.10 V versus saturated calomel electrode （SCE） for 5 rain. By adopting three-electrode cell and square wave voltammetry, Hg-Au microelectrode can measure dissolved oxygen, Mn^2＋ , Fe^2＋ and sulfide during a single potential scan from -0.10 V to - 1.75 V versus saturated calomel electrode. Experimental results indicated that the micro- electrode has the sensitivity and detection limit of 0. 16 nA/（ μmol/L）, 6 μmol/L for dissolved oxygen; 0.35 nA/（μmol/L） , 3 μmol/L for Mn^2＋ ; 0.22 nA/（μmol/L） , 5 μmol/L for Fe^2＋ and 34 nA/（μmol/L） , 0.03 μmol/L for sulfide. It was found that the microelectrode exhibits good reproducibility with an error of within 3 % after measuring 15 sediment samples consecutively.