Background:

Perchlorate as potassium perchlorate or ammonium perchlorate is widely used in a variety of military munitions, ranging from solid rocket fuel to simulators. The combination of its widespread use and potential health impacts make it a high-priority military contaminant. Federal and state authorities have pressured installations to take action using interim action levels and health advisories. Current methods for measuring perchlorate at the critical part per billion (ppb) level, however, rely largely on benchtop instrumentation that must be located in a centralized laboratory. Alternative fieldable sensing approaches for perchlorate have been confounded by the presence of interfering species whose concentrations are orders of magnitude higher than perchlorate.

Objective:

The objective of this project is to study zwitterionic surfactant chemistry to create a miniaturized sorption zone that selectively and controllably binds and releases perchlorate in the presence of excess common environmental anions such as nitrate and chloride. This novel concentration zone will be embedded onto a microfluidic sensor platform that will test its ability for perchlorate extraction and concentration to provide rapid (less than 10 minutes per sample), sub-ppb analysis of perchlorate in surface water and groundwater samples. In this limited scope effort, the underlying chemical basis for the extraction technique will be studied with an aim towards developing a fieldable sensor in a follow-on effort.

Process/Technology Description:

Lab-on-a-chip (LOC) devices offer the potential to integrate all steps of a chemical analysis method into a single inexpensive package that works autonomously, but few are plausible for the analysis of low abundance environmental contaminants. Previous efforts by the research team have established one variant of LOC technology—microchip electrophoresis—as a viable sensing option for perchlorate at the sub-ppb level when samples contain low concentrations (sub-part per million) of interfering ions. When perchlorate water samples containing high levels of chloride and nitrate were tested, nonlinear calibration curves were required and accuracy was greatly diminished. In this project, a novel extraction chemistry that uses zwitterionic surfactants immobilized on either a conventional or membrane-based stationary phase (electrostatic ion chromatography) embedded at the injection end of a microfluidic device will be used to extract and concentrate perchlorate from contaminated water samples prior to analysis by microchip electrophoresis/contact conductivity. Zwitterionic surfactants can selectively bind anions based on their interaction with the central cationic group for betaine-type surfactant molecules. Researchers will study these properties to identify specific surfactants' selective affinity towards perchlorate.

Expected Benefits:

Combining perchlorate affinity chemistry with LOC detection devices to create sentinel structures for real-time automated determinations of perchlorate in the environment will lead to many benefits over existing approaches. First, it will be faster than existing methods, giving analysis times of less than 10 minutes as opposed to the days currently required to collect, ship, and analyze samples in a central laboratory. Second, it will be cheaper ($1 versus $100s per sample) than existing methods since labor is curtailed and inexpensive instrumentation can be used. Third, the designed system will have even lower limits of detection due to the concentration effect of the immobilized surfactant chemistry. The combination of speed and low cost would allow comprehensive range characterization to locate sources and movement of contaminants. Furthermore, it is important to note that, while the system will be tailored for perchlorate, this platform design can be modularized for the selective extraction and analysis of other low-abundance contaminants from complex media. (Anticipated Project Completion - 2010)

Contact Information:

Dr. Donald Cropek 
U.S. Army Corps of Engineers
Engineer Research and Development Center
Construction Engineering Research Laboratory
P.O. Box 9005
Attn: CEERD-CN-E (Cropek)
2902 Newmark Drive
Champaign, IL 61822 
Phone: (217) 373 6737
Fax: (217) 373-7222
E-mail: donald.m.cropek@usace.army.mil