Metrohm 757 VA Computrace - Manual (Page 165)

7.8 Work with film electrodes
757 VA Computrace – Software
155
7.8 Work with film electrodes
Deposit a mercury film
You find a suitable method for the determination of heavy metals
with mercury film electrodes in Application Bulletins 241 and 254.
1. Polish the glassy carbon (6.1204.110) or Ultra Trace electrode
tip (6.1204.100) with alumina powder (6.2802.000) and put
the electrode into the 757 VA Computrace Stand.
2. Put the plating solution into the measuring vessel, e.g.:
Add 10 mL ultrapure water, 200 µL c(HCl) = 6 mol/L) and 50
µg c(Hg(II)) = 1 g/L to the empty measuring vessel at the 757
VA Computrace Stand.
3. Click on MAIN WINDOW / Utility / Film deposition to open the
FILM DEPOSITION window.
4. Enter suitable parameters in the parameter list.
5. Click on the
<Start> button.
6. Check the resulting test voltammogram. The voltammogram
should show low noise and a low background current (low µA
range). No interfering peaks should be visible.
Remove a mercury film
Mercury films can be easily wiped off manually with a tissue. The
cleaning procedure can be used instead to remove the mercury
film electrochemically or to clean the electrode surface after hav-
ing removed the mercury film mechanically.
1. Put the cleaning solution into the measuring vessel, e.g.:
Add 10 mL ultrapure water and 1 mL w(HNO
3
) = 0.65 to the
empty measuring vessel at the 757 VA Computrace Stand.
2. Click on MAIN WINDOW / Utility / Cleaning procedure to open the
CLEANING PROCEDURE window.
3. Enter suitable parameters in the parameter list.
4. Click on the
<Start> button.
5. Check the resulting test voltammogram. The resulting volt-
ammogram should show low noise and a low background
current (low µA range). If all mercury had been oxidized, no
mercury peak remains.