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| The SVET
(Scanning Vibrating Electrode Technique) |
more details |
| The SVET (Scanning Vibrating Electrode
Technique) can measure voltage gradients down to nanovolts at a minimum speed of
approximately 50 mS per scan point. Voltage gradients are
not disturbed by the electrode’s vibrations, which are typically 200 Hz
to 1.0 kHhz. The 2D
vibration is accomplished by use of piezoelectric wafers driven by The
PSD-2 sine-wave oscillators.
Scanning is done with a 3D stepper motor micromanipulator (CMC-4). The SVET system is also
capable of Electrochemical Impedance Spectroscopy measurements. We call this SLEIS
(Scanning Local Electrochemical Impedance Spectroscopy). We are currently developing this
technique to improve system capabilities.
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| The
SLEIS (Scanning Localized Electrochemical Impedance Spectroscopy |
more details |
| The SLEIS
(Localized Electrochemical Impedance Spectroscopy) can measure
below the 1.0 kHz range (typically 30-100 Hz). Essentially, one leaves
the microelectrode stationary (non-vibrating) and then the
sample is driven with the oscillators in the PSD-2 amplifier, either directly,
or via a potentiostat. Another
mode is available as well to allow one axis to measure as an SVET and
the other to measure as an LEIS simultaneously while scanning the
probe over a sample under potentiostat control. These methods of
measurement provide the user with high sensitivity and a spatial
resolution limited by the electrode tip, typically 5-50 µm diameter.
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|
The SIET
(Scanning Ion-selective Electrode Technique)
|
more details |
| The SIET (Scanning Ion-selective Electrode
Technique) can measure ion concentrations down to picomolar levels but must be
measured slowly at around 0.5 to 1 second per point. This is mainly due to the mechanical
disturbance of the gradient by the electrode movement, although the time constant of the
LIX (Liquid Ion Exchange) electrodes is also a factor. It takes a fraction of a second to
re-establish the
gradient again. LIX electrodes also have time constants in tenths
of seconds (LIX dependent, see LIX specs). The electrode is stepped from one position to
another in a defined sampling routine while being scanned with the 3D micro-stepper motor
manipulator (CMC-4).How
does the SIET work? -
see a
movie clip
|
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 |
| The SPET
(Scanning Polarographic Electrode Technique) |
more details |
| The SPET (Scanning Polarographic Electrode
Technique) can measure dissolved oxygen gradients in aqueous media down to a fraction of a
percent of concentration. The electrode is polarized to create a reduction reaction on the
electrode tip. The system is programmed to do automatic polarization plots of the electrode at
different voltages to determine the best operating voltage. This system is capable of
detecting less than a 0.01% change in dissolved oxygen over a 10 µm excursion using a computer
adjustable repetitive positioning algorithm as with the SIET. Different types of
polarographic electrodes can be utilized as well. Currently, Clark and Whalen type
polarographic electrodes are used. Nitric Oxide and hydrogen peroxide
electrodes can also be used. Basically, any polarographic electrode
can be used with the system.
 |
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