Metrohm 746 VA Trace Analyzer - Manual (Page 393)

5.7 Program instructions
746 VA Trace Analyzer / 747 VA Stand
5-242
HMDE Page: O, S Stand: M, A Abbreviation: H
Instructions t/s Main parameters Auxiliary parameters
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## .. HMDE ..... Drop size ........ Meas.cell ........
Function Switch on Hanging Mercury Drop Electrode (HMDE).
Application The HMDE is primarily used for very sensitive stripping voltammetry in
which the analyte species is not measured until it has first been
electrochemically enriched. Cyclic voltammetry and PSA are also
possible with the HMDE.
Parameter Range; Default value / Meaning
Drop size 1...9; 4
Drop size
Setting of the size of the mercury drop.
The area of the drop is ca. 0.15 mm
2
( 1 ) ... 0.60 mm
2
( 9 ).
The set drop time t.drop important for certain parameter settings is
0 ms for the HMDE by definition.
Meas.cell normal, EFTA; normal
Operation mode
Setting of the operation mode for the HMDE:
normal Normal operation for MME in measuring vessel:
4 mercury drops of defined size are formed in succes-
sion at the MME. The last drop remains suspended
EFTA Operation for EFTA cell (future application):
The valve for Hg outflow is opened until two drops have
been expelled. After a waiting time of 300 ms a new Hg
drop of the defined size
Drop size is formed and re-
mains suspended.
Description The HMDE instruction is used to form mercury drops of defined size at
the 6.1246.020 Multi-Mode Electrode. The last drop remains suspended
and thus forms the hanging mercury drop electrode at which a voltage
sweep can be performed.
t
F (Hg)
t.HMDE
Area (Hg)