Final Report: Microelectrode Array to Enable Robust Water Monitoring for Multiple Contaminants at Sub-Nanomolar ConcentrationsEPA Contract Number: EPD12017
Title: Microelectrode Array to Enable Robust Water Monitoring for Multiple Contaminants at Sub-Nanomolar Concentrations
Investigators: McCrabb, Heather
Small Business: Faraday Technology, Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2012 through August 31, 2012
Project Amount: $80,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2012) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Drinking Water Treatment and Monitoring
Current methods for detecting and monitoring inorganic and organic water contaminants often involve sampling the water at its source and transporting it to a laboratory for analysis with sophisticated laboratory equipment operated by specially trained scientists. Testing can be expensive, and the results of these tests may not be received for days or even weeks, delaying action if the water is found to be contaminated. It has been recognized that a need exists for water contaminant measurement/monitoring techniques that are inexpensive, produce rapid results, are easy to use and have low potential for false positive/negative readings. Faraday Technology, Inc., proposed a sensor based on an ion-selective microelectrode containing a polymer membrane that utilizes ion-transfer stripping voltammetry for cationic and anionic analyte detection without the need for a rotating electrode or mercury film. This effort builds upon the work of Prof. Shigeru Amemiya at the University of Pittsburgh who demonstrated the feasibility of the analyte detection using a rotating electrode. This technology supports the EPA's initiatives to promote development of novel water monitoring technologies, initially within the recently formed EPA Cincinnati/Dayton/Northern Kentucky water technology cluster, and subsequently throughout the United States.
The work performed in this Phase I program demonstrated the feasibility of using ion stripping voltammetry with ion-selective electrodes made of organically modified gold containing a thin PVC membrane for detecting ClO4- down to a concentration of 10 ppb, which currently is lower than the 15 ppb health advisory limit set by the EPA. Additionally, a separate organically modified gold ion-selective electrode containing a thin PVC membrane for lead (Pb) detection was demonstrated for aqueous solutions contaminated with Pb down to concentrations of 0.2 ppb, well below the EPA health advisory limit of 15 ppb. The sensors offer an alternative method for contaminant monitoring and detection that is easier to operate, provides results in a more timely fashion and is more affordable than conventional laboratory-based methods. The thickness of the redox reactive organic layer and the PVC membrane were experimentally optimized to maximize the sensor sensitivity. A microelectrode array sensor was conceptually designed that would enable (1) a boost in the signal response to further improve the sensor sensitivity, and (2) detection of multiple contaminant species with a single sensor if desired. A preliminary cost estimate of the microelectrode array was developed to demonstrate the economic benefits this technology has to offer relative to more expensive and time-consuming laboratory-based methods.
In summary, Faraday has demonstrated the feasibility of the ion-selective microelectrode sensor concept for ClO4- through the fabrication of the microelectrode and the detection of ClO4- at levels slightly lower than the EPA health advisory limit. Additionally, detection of Pb contamination in water was demonstrated by Prof. Amemiya using an organically modified gold RDE. This technology has applicability to a wide range of other analytes of interest to the water treatment community, including chromate and arsenate species.