The VIPPlus presents important and unique features for environmental applications, in particular:

• In situ water column profiling (i.e. no sample collections).
• Continuous, real-time monitoring.
• Flexibility of operation: spot or autonomous long-term monitoring.
• Profiling capability between 0 to 500 meters depth.
• Autonomous data analysis (post processing) and transmission.
• Light, robust and easy handling system.
• Low power consumption.
• Novel, long-term reliable gel-integrated array working electrode.
• Fouling problems minimized thanks to the novel gel-integrated working electrode.
• High sensitivity (detection limit down to 50 pM).
• Simultaneous trace elements analysis: i.e. Cu(II), Pb(II), Cd(II), Zn(II) at the ppt level and Mn(II), Fe(II) at the ppb level. Possible extension to other compounds.
• Chemical speciation capability.
• Suitable for marine and fresh waters.
• Easy combination with CTD, oxygen, pH, Redox, Fluorometer, Turbidity meter sensors.
• Data storage in a SD flash memory card for a high data retention and protection.
• Electrochemical techniques available:
  • Chrono-amperometry.
  • Linear Sweep Voltammetry (LSV).
  • Cyclic Voltammetry (CV).
  • Square Wave Voltammetry (SWV).
  • Square Wave Anodic Stripping Voltammetry (SWASV).
  • Other electrochemical techniques can be readily implemented.
• Pre-cleaning step.
• Temperature variation effect can be corrected.
• Voltammetric signals are independent of the pressure.
• Automated measurement and subtraction of the “real” background current.
• Multiple experimental runs.
• Digital data smoothing by means of the Savitsky-Golay algorithm.
• Advanced computer controlled analysis through the VIPPlus Windows management software.
• Automated and manual peak finding routines; Data storage: Binary, Excel, and text format.

The electronic housing is composed of acetylic copolymer (POM) tube and flanges with o-ring seals. This housing withstands pressure up to 150 bars (i.e. 1500 meters depth). The connectors are located on the upper flange. The lower flange holds the cell assembly. The electronic housing contains all the hardware and firmware necessary to manage:

• The voltammetric measurements.
• The interfacing of the OS316Plus (optional; via RS232C interface) and the submersible pump.
• The data transfer by telemetry and/or RS232C.
• The interfacing of the single or double peristaltic pump unit.

The flow-through voltammetric cell of the submersible VIPPlus is based on a three-electrode system. It has been specifically designed for in situ measurements based on the following criteria:

• Positioning of the three electrodes in order to:
  • Prevent the products formed at the reference and counter electrode to interfere at the working electrode.
  • Minimize the attachment on the working electrode tip of gas micro-bubbles formed by temperature changes.
  • Minimize electrical resistance thanks to very short distances between the different electrodes.
• Robustness.
• Possibility of maintenance and/or replacement of the working, reference and counter electrodes in field conditions.
• Pressure compensation.

The submersible pump is a specially built peristaltic pump fixed at the bottom of the pressure case base or joined laterally to the VIPPlus electronic housing.
The motor pump is located in housing similar to that used for the VIPPlus electronics. The peristaltic pump head and the motor pump are linked together through a rotating axis. These mechanical linking parts have been carefully manufactured to ensure water tightness and proper functioning of the submersible pump down to 500 m without the requirement of an oil immersion system. The fittings used for sampling are standard 1/4″ 28 thread fittings made of inert, metal free Teflon materials. The tubing used for the fluidic system is in Teflon or Tygon.