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, 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 14).
There are two preliminary steps needed for 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 solution) in colour.
The element being test determines the plating solution required:
HG500 Hg Plating Solution – Cd, Pb, Cu, Zn, Sb, Bi, Co, Tl
AU500 Au Plating Solution – Hg and As
HG1000 Thick Hg Plating Solution – Mn, Se, Sn
AU1000 Thick Au Plating Solution – Cr (VI)
WE1 is used for Cd, Pb, Cu, Zn, Sb, Bi, Co, Tl, Mn, Se and Sn analysis
WE2 is used for Hg and As analysis
WE3 is used for Au and Ni analysis
Chromium Electrode is used for Cr (VI) analysis only
It is necessary to perform the plating and conditioning steps 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), the
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.
When using the Metaware on the tablet PC, the conditioning of the
electrode occurs when the M group of interest is selected from the
Measurements Available drop down menu. If using the instrument directly,
select the method of interest from the Test Methods menu, then choose
the conditioning step which will be at the top of the list. The conditioning
step should be carried out in samples water and undertakes a run which
sensitises the Working Electrode.
Metalyser® Field Pro HM3000 Instruction Manual v 5.0
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