Metalyser
®
Portable HM1000
Instruction Manual v 5.0
19
5.2. PLATING
This is a process used to form a very thin plate on the surface of the working electrode and only
takes a few minutes to complete. The plating step is necessary prior to the analysis of each
element, however it is possible to analyse elements consecutively if they share a common
plating solution (e.g. Cd, Pb, and Zn all use HG500 Hg Plating Solution). Before carrying
out the plating step, the Working Electrode surface must be polished to remove any
scratches and imperfections (see page 12).
There are two preliminary steps needed for any analysis with the Metalyser
®
.
The plating step uses either the HG500 Hg Plating Solution or AU500 Au Plating
Solution, added to the SAB, to form a plate on the working electrode. After plating,
the mirror-finish black tip is covered with a plate that is either grey (HG500 Plating
Solution) or yellow/gold (AU500 Plating Solution) in colour.
The element being tested determined the plating solution required:
HG500 Hg Plating Solution
– Cd, Pb, Cu, Zn
AU500 Au Plating Solution
– Hg and As
HG1000 Thick Hg Plating Solution
– Mn
AU1000 Thick Au Plating Solution
– Cr(VI)
WE1 is used for Cd, Pb, Cu, Zn and Mn analysis
WE2 is used for Hg and As analysis
WE3 is used for Ni analysis
Chromium Electrode is used for Cr(VI) analysis only
It is necessary to perform the plating and conditioning before an analysis session or
if the sensitivity of the analysis decreases. This is because, over time, the plate will
reduce in thickness and eventually come off. Typically this would be after 20+
consecutive samples or a period of 2-3 hours. It is therefore suggested to regularly
re-plate the electrode; if analysing a lot of samples, it is recommended to plate in
the morning and again at the beginning of the afternoon session.
If in doubt, remove the old plate by wiping the surface, polishing the tip of the
Working Electrode to a mirror-finish (with the polishing kit provided), rinse with
the wash bottle and perform a new plating.
When analysing for elements requiring a plate different to the one currently being
used, the electrode not in use will need to be removed from the sonde to prevent
interference. It is advised to group together analyses using the sample plate to
save switching between them.
The conditioning of the electrode occurs when the element of interest is selected in the
Test Methods
menu, then choosing condition electrode, which is at the top of the list
for the selected electrode. The conditioning step should be carried out in sample water,
and undertakes a run which sensitises the Working Electrode.
