19
Metalyser
®
Soils HM4000
Instruction Manual v3.0
3.3.2. 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 required for any analysis with the Metalyser
®
. The
plating step uses the HG500 Hg Plating Solution, HG1000 Thick 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 (Hg Plating Solutions) or yellow/gold (Au Plating Solutions).
The element being tested determines the plating solution required:
HG500 Hg Plating Solution
– Cd, Pb, Cu, Zn
AU500 Au Plating Solution
– Hg and As
WE1 is used for Cd, Pb, Cu and Zn analysis
We2 is used for Hg and As analysis
It is necessary to perform the plating and conditioning before an analysis session or if
the sensitivity of the analysis decrease. This is because, over time, the plate will reduce
in thickness and eventually come off. Typically this will 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), then 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 same plate to save
switching between them.
The conditioning of the electrode occurs when the element of interest is selected in the
Test Methods
menu and 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.
