用微量汞提高测银灵敏度——玻碳电极溶出伏安法

当微量Ag~1、Hg~(2+)(10~(-7)M～10~(-9)M)共存于溶液(用HCl调pH为2的0.1MKSCN)中时,用普通极谱仪在-1.5V(VS、Ag/AgCl、盐桥联接),电解沉积2～10分钟,-0.3V～+0.2V溶出,在+0.12V出现一个很好的Ag-Hg金属间化合物溶出峰,它比Ag~+或Hg~(2+)单独存在时的溶出峰灵敏得多,并与两者的峰高、峰形、峰电位都有显著不同。当Hg~(2+)浓度一定时、峰高与Ag~+浓度呈正比,反之亦然。用标准加入外推法外延工作曲线至横轴,便能直接读出被测液中Ag~+浓度。

Improvement of Sensitivity of Determing Silver by Microamount Mercury (lonSt ripping Voltammetry by Glass Carbon Electrode)

When a 20 ml solution of 0.1M KSCN in which pH is adjusted topH 2 by hydrochloric acid contains trace of 10~(-7) M to 10~(-9) M Ag~+ andHg~(2+) ions and produces electrolysis for 2 to 10 minutes uuder the con-ditions of the sweeping range of -0.3 to + 0.2v a very good strip-ping peak of the Ag - Hg intermetallic compound appears, the sensiti-vity of this peak is much hihger than that of the presceuce of Ag~+or Hg~(2+) ion alone. In addition, this peak height, peak shape and peakpotential for the former is very different from that for the latter.When the concentration of Hg~(2+) ion is given, the peak height is pro-potional to the concentration of Ag~+ ion and vice versa. If one usesthe method of extrapolation standard addition to extrapolate the stan-dard curve to the abscissa, the contentration of Ag~+ in the testingsolution may be read directly.