Ultra-sensitive Ion Selective Electrode

Physical Sciences : Materials and Compounds

Available for licensing


  • Bradley Holliday, Ph.D. , Chemistry and Biochemistry

Background/unmet need

Access to clean and safe drinking water is one of the most significant problems facing millions of people in both rural and urban settings in developing countries. Due to contamination from mining activities, industrial processes, and unsafe products, water supplies are often contaminated with heavy-metal ions such as lead (Pb), cadmium (Cd), and/or mercury (Hg).

With continuous consumption, these toxic heavy metal ions are known to cause a variety of diseases and disorders. Children are particularly vulnerable to these metals and will often experience a variety of developmental problems when even very small amounts of these metals are in their drinking water supply.

Unlike biological contaminants, boiling of the drinking water will not eliminate these metals. Thus, developing a low-cost, robust, and user-friendly technology for everyday monitoring of trace metal ions in drinking water is extremely important.

Among many detection methods, Ion Selective Electrode (ISE) is an easy-to-operate, low-cost, and reliable method. However, typical ISE detection limit for Pb is 200ppb, significantly higher than the Pb standard of 10 to 15 ppb set by the European Union and U.S. EPA for drinking water.

Invention Description

A group of UT Austin researchers in the Chemistry Department has discovered a technology that can reduce the ISE detection limit of Pb, Hg, and Cd, among other heavy metal ions, to much lower levels. This invention comprises a synthetically modified conducting polymer backbone with chelating groups that specifically and selectively bind to heavy-metal ions.The conducting polymer backbone exhibits changes in its conductivity when the polymer material is exposed to metal ions in either aqueous or non-aqueous solutions.

The changes in conductivity (or resistance) are very simple to measure and can be readily integrated into commercially available voltmeters used in ISE. Detection limit on Pb can be reduced to as low as 2 ppb. Additionally, unlike standard ISE, this type of materials does not need aqueous storage environment, further simplifying its operation. Therefore, this invention represents a new type of ion selective electrode that is simple, low-cost, robust, highly sensitive, and highly specific.


  • Highly selective and sensitive detection of heavy-metal ions in both aqueous and non-aqueous samples
  • Very low limits of detection for ions such as lead
  • Simple and inexpensive to produce sensing devices
  • Robust to prolonged dry storage
  • Easy sensing readout that does not require bulky or expensive equipment
  • Simplified design, which leads to prolonged use without degradation
  • Can be modified to gain selectivity for other metal ions or small molecules such as biological toxins or chemical warfare agents


  • This new conducting polymer material can be made into a thin-film coating on a supporting substrate to form a Ion Selective Electrode.
  • This material selectively binds heavy-metal ions such as lead in the presence of other metal ions that are often present in drinking water.
  • The binding changes the conductivity of the polymer material very sensitively. This conductivity change can be easily measured by readily available voltmeter.
  • The polymer material is robust to storage under standard conditions for over a year. It does not need be stored in a buffered solution continuously.

Market potential/applications

Low-cost drinking water test kits; sensing devices for industrial applications; biomedical diagnosis for both in vivo and in vitro applications 

Development Stage

Lab/bench prototype