Grantee Research Project Results

Final Report: Real-Time Multi-Parameter Analysis of Pollutants in Stormwater and Other Complex Analyte Matrices Using Electrospray Ionization-Ion Mobility Spectroscopy

EPA Contract Number: 68D03067
Title: Real-Time Multi-Parameter Analysis of Pollutants in Stormwater and Other Complex Analyte Matrices Using Electrospray Ionization-Ion Mobility Spectroscopy
Investigators: Coleman, Thomas E.
Small Business: dTEC Systems LLC
EPA Contact: Richards, April
Phase: II
Project Period: October 1, 2003 through December 31, 2004
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2003) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , Ecological Indicators/Assessment/Restoration , SBIR - Monitoring

Description:

The overall goal of this research project was to develop a prototype portable electrospray ionization ion-mobility spectroscopy (ESI-IMS) analytical system that will be applicable to the monitoring of stormwater runoff as well as combined sewer overflows. This system also will be applicable to monitoring drinking water treatment systems for regulated and unregulated contaminants. This ESI-IMS system is intended to enable real-time aqueous phase measurement of conventional parameters such as ammonia, phosphorus, nitrate, and nitrite as well as other toxic organic and inorganic compounds in the field without the need for transportation of samples or complex sample preparation.

The specific goals of this research project were to:

• Design and assemble a prototype portable ESI-IMS instrument with the objective of optimizing the price/performance capabilities of the instrument.

• Identify complexing agents that can enhance the resolution and detection limits for the analysis of metals using ESI-IMS.

• Identify solvent mixtures and solvent modifiers that will enable improved performance for detection of the analytes of interest in stormwater and other environmental samples.

• Identify surfactant additives that will enable direct analysis of 100 percent aqueous solutions.

• Demonstrate the application of ESI-IMS for the analysis of neutral (relatively nonionizable) organic compounds through the addition of sodium ions or nitrate ions to form sodium or nitrate adducts.

• Demonstrate the portable prototype ESI-IMS instrument for real-time monitoring of stormwater and other water-quality monitoring applications.

Summary/Accomplishments (Outputs/Outcomes):

A compact portable ESI-IMS instrument was developed and successfully demonstrated for the analysis of aqueous samples representative of stormwater or other environmental sample matrices. This prototype will serve as an excellent platform for further development and commercialization of this technology.

dTEC Systems, LLC, optimized the performance of the IMS and electronics components in terms of signal-to-noise capabilities. Despite these improvements to the IMS instrument design, significant improvements could not be demonstrated in resolution or detection limits for the analytes of interest as compared to the results obtained in Phase I. One of the significant challenges remaining is the development and better understanding of the electrochemical transformations, which various chemical species undergo during the ESI process. The current sensitivity and resolution capabilities of the instrument seem to be most limited by the variable nature of the electrospray process itself. This represents both a challenge and an opportunity to develop valuable intellectual property specific to the development of commercial applications for stormwater monitoring and other environmental sample analytical systems. The primary area of focus must be aimed toward initial followup research and development efforts.

Among the other positive results that have been demonstrated is the ability to obtain spectra from 100 percent aqueous samples and aqueous samples containing very small additions of surfactants. Further development is necessary in this area, but it is another encouraging outcome of this research project.

The experiments that introduced complexing agents and adducts to the sample matrices in an effort to enhance the resolution and detection limits for the analysis metals and organics, respectively, did not yield the intended results. dTEC Systems’ hypothesis was that the use of complexing agents would make it possible to form stable ion complexes with selected metals. The multiple peaks demonstrated by metals such as copper (Cu²⁺) were not consolidated into a single larger peak as had been hoped, nor were the intensities of the individual peaks increased.

dTEC Systems was able to demonstrate the use of a resistive glass material as an alternative method for drift tube construction in a benchtop demonstration experiment. The potential advantages of this method for drift tube assembly include lower cost, greater durability, and simpler and more compact instrument designs. Ion mobility spectra were obtained with the test instrument assembly, but thus far the peak intensities have been significantly lower than the peak intensities obtained with the discrete ring drift tube design. Nevertheless, this result is encouraging because the resistivities of glass tubes available for these experiments had not yet been optimized in terms of this application.

Conclusions:

As a result of this research project, dTEC Systems developed a compact portable ESI-IMS instrument that will serve as an excellent platform for followup research and commercialization. Several areas have been identified that represent promising opportunities for future research and development to improve the ESI-IMS instrument performance and to further reduce costs. These opportunities include:

• Develop a two-gate ESI-IMS with Fourier transform to improve resolution and detection limits.

• Continue investigating resistive glass material drift tube construction methods.

• Redesign the ion gate driver using a battery instead of the isolation transformer to reduce cost and improve reliability.

• Redesign the amplifier to enable greater separation from the drift tube.

• Design a microprocessor-based stand-alone A/D converter and signal processor to replace the laptop computer, the proprietary interface, and the proprietary software for spectra generation.

Another important potential commercial application for ESI-IMS is as a real-time method for identifying biological and chemical terror agents in drinking water and surface water. This “higher value” application of ESI-IMS, while not the focus of this Phase II research project, might have better initial market acceptance than the application of ESI-IMS for stormwater monitoring, where regulatory and performance standards are not yet fully defined. Therefore, the ideal commercialization partner would have product lines and interests covering a wide range of water quality monitoring systems, including homeland security applications. dTEC Systems has received significant recent interest from two such major companies and will be meeting with them in the near future to discuss collaborative agreements for followup commercialization efforts for this technology.

Supplemental Keywords:

pollutant analysis, stormwater runoff, combined sewer overflows, CSO, monitoring, electrospray ionization-ion mobility spectroscopy, ESI-IMS, metals, nutrients, pollutants, EPA, small business, SBIR,, RFA, Scientific Discipline, Water, TREATMENT/CONTROL, POLLUTANTS/TOXICS, Ground Water, Wastewater, Environmental Chemistry, Arsenic, Environmental Monitoring, Wet Weather Flows, Water Pollutants, Engineering, Chemistry, & Physics, Environmental Engineering, Water Pollution Control, aqueous impurities, real time analysis, wastewater treatment, water contamination detection, combined sewage outflows, electrospray ionozation, analytical measurement methods, contaminated waters, electrospray mass spectrometry, runoff, urban runoff, analytical chemistry, municipal wastewater, aqueous waste, water quality, wastewater discharges, ion mobility spectroscopy, real time monitoring, storm drainage, stormwater runoff, aqueous waste stream

SBIR Phase I:

Real-Time Multi-Parameter Analysis of Pollutants in Stormwater and Other Complex Analyte Matrices Using Electrospray Ionization-Ion Mobility Spectroscopy  | Final Report