The SIET (Scanning Ion-selective Electrode Technique) can measure ion concentrations down to picomolar levels but must be measured slowly at approximately 1-2 seconds 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 Exchanger) electrodes is also a factor. It takes a fraction of a second to reestablish the gradient. The electrode is stepped from one position to another in a defined sampling routine while also being scanned with the 3D micro-stepper motor manipulator (CMC-4). 1,2,3D or complex measurement paths are user programmable.
The SPET (Scanning Polarographic Electrode Technique) can measure dissolved oxygen gradients in aqueous media down to a fraction of a percent of concentration. An electrode is polarized to create a reduction reaction on the electrode tip. Different types of polarized electrodes can be utilized as well. Clark, Whalen and cathode type oxygen electrodes, carbon fiber based nitric oxide electrodes can be used along with many other types of polarized electrodes.
The SVET (Scanning Vibrating Electrode Technique) can measure voltage gradients down to nV levels at a minimum speed of approximately 50 ms per scan point. Voltage gradients are not disturbed by the probe’s vibrations, which are typically 200 Hzto 1.0 kHz. The 2D vibration is accomplished by use of piezoelectric wafers driven by sine wave oscillators. The PSD-2 amplifier was designed for SVET applications.
The PSD-2 amplifier and preamplifier are also capable of SLEIS (Scanning Localized Electrochemical Impedance Spectroscopy) measurements below the 1.0 kHz range (typically 30-100Hz). Essentially, one leaves the microelectrode stationary (non-vibrating) and then drives the sample with the oscillators in the PSD-2, 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 SLEIS 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.
DVIT (Differential Video Imaging Technique) is an in situ technique for locating sites of corrosion on a metal surface. A color CCD camera is used to acquire a series of images of the surface. By using our proprietary algorithms to analyze small differences between these images, sites of corrosion initiation may be identified and characterized. DVIT is, then, a difference imaging method.
DVIT may be done with a chemical indicator dye in solution. For example, a pH indicator may be used to locate sites where pH changes more than at surrounding points on a metal surface.
DVIT may be combined with SVET or SIET, to simultaneously acquire data with DVIT and another of those techniques.
The spatial resolution that DVIT can attain depends on the camera resolution, and the microscope magnification used.
Applicable Electronics sells a system that includes everything you need for DVIT. It includes:
A megapixel color CCD camera, along with electronics required to digitally transfer images to a PC. The camera is mounted to a zoom microscope. The PC-controlled light source is specially stabilized, and includes switchable optical filters.
Difference Viewer, a software package that allows the user to acquire and analyze series of images. The software is run from an easy-to-use graphical user interface (Labview-based). It allows you to analyze image differences, using our algorithms. DIFFERENCE VIEWER software also allows you to collect analog voltages during an experiment (such as potentiostat outputs). Graphs of those logged voltages may be plotted as you analyze the experiment.
For an example of DVIT data, click here.
SMOT – Scanning Micro Optrode Technique
The Scanning Micro Optrode Technique employs a blue LED source light and a fiber optic sensor sensitive to dissolved oxygen in solution. Spatial resolution is currently in the 10 micrometer range with commercially available optrodes. This is a measurement of the light shift as a function of quenching associated with dissolved oxygen concentration in solution. This measurement requires only the optrode and no reference electrode.
Contains the following equipment:
DELL PC and Monitors
ASET-LV4 software for scanning microelectrode techniques
Vibration Isolation Table
Two channel Oscilloscope
uEYE USB digital camera
Microscope and lamp supply
CMC-4 Four axis motion controller w/3D motorized micromanipulator.