Motivation for InSitu Sensors

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Motivation for In-Situ Sensors

• Environmental Science
• Environmental Monitoring
• Industrial Monitoring
• Desirable characteristics
• results while you wait
• stable over the long term
• easy to calibrate
• low detection level
• high accuracy

Photo courtesy of USGS
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Philosophy

• The criteria behind chemical sensing have
  involved the design of small single molecules
  that specifically recognize a single ion or a
  molecular species in a competitive media in a
  reversible manner and in a given concentration
  range." -- (Gunnlaugsson et al. 2006)
• In truth
• It is difficult to sense a single molecule with
  high specificity
• Even when the sensors are good, the development
  process is very costly (and slow)

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Proposal Multi-Electrode Analysis

• Use a variety of types of sensors (ion selective
  electrodes, fluorescence techniques,
  semiconductor, optical, UV absorbance,
  colorimetric, polarographic) to measure the ion
  suite of interest
• Include sensors measuring non-ionic quantities
  (pH, temperature, etc.)
• Adaptive/Predictive signal processing techniques
  (e.g. artificial neural networks with feedback)
  extract improved signals for all ions
• Intended application in-situ analysis of
  surface waters

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Potential Ion Sets of Interest

• Nitrogen Species
• electrodes out there for nitrate/nitrite/NO
• might be challenging to find them with low enough
  detection levels
• NH4 (needs K, Na to compensate)
• in-situ gas probes?

• Environmental Anions of Interest
• nitrate/nitrite
• carbonate
• Cl-
• SCN-
• I-
• F-
• etc.

5
Proof of Concept Suite of Metals (Vlasov and
Legin)
From Vlasov, Y and A. Legin (1998)
Non-selective Chemical Sensors in Analytical
Chemistry from electric nose to electric
tongue J Anal Chem 361 255-260.
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Commercially Available Probes
Partially taken from Daly et al 2004