Final Report: Field Deployable PFCs Sensors for Contaminated Soil ScreeningEPA Contract Number: EPD14012
Title: Field Deployable PFCs Sensors for Contaminated Soil Screening
Investigators: Chen, Li
Small Business: United Science, LLC
EPA Contact: Richards, April
Project Period: May 1, 2014 through April 30, 2015
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2014) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Cleanup of Contaminated Sediments
Perfluorooctanesulfonate (PFOS–) is an anionic surfactant species that is a member of a large family of ubiquitous and emerging environmental contaminants known as perfluoro chemicals (PFCs). Soil and groundwater contamination by PFCs have been caused by legal emissions from industrial manufacturers (carpets, lubricants, paints, packaging, cookware); protectant spray consumer products; polymer producers; fire fighting foams; and chromium plating facilities. Preliminary assessment of contaminated sites is underway but are extremely costly and time consuming. This is due in part to the complicated requirements for analysis of PFC contaminated samples. Proper analysis requires expensive and highly specialized laboratory equipment and personnel (Ph.D. level) for effective sampling, sample preservation, sample preparation and analytical methods. Off-line and off-site LC/MS/MS analytical methods have been shown to have the selectivity and low limits of detection required for PFOS– measurement. However, the total analysis price/sample is costly and is driven in part by time consuming (30-60 days) sample preparation in a wide variety of matrices with co-contaminants. Furthermore, long-term monitoring costs become intolerable under these parameters.
Recent work has shown that ion selective electrodes (ISEs) fabricated from fluorous materials can be used to measure PFOS– in drinking and ground water down to the ppt level with no sample preparation. However, PFCs become trapped in the compact soils above aquifers and can slowly elute into groundwater over time. PFCs are also likely transported away from the source via rivers, creeks or stormwater routes. All major sources of PFCs and transport pathways are typically identified to properly remediate. However, current analysis methods are not amenable to wide spatial and temporal sampling. Furthermore, most of the site assessment work at known PFC contaminated sites has sorely focused on PFC levels in groundwater. The goal of this research is to demonstrate the effectiveness of a hand held PFC ISE device that can screen for the presence of PFCs in soils and enable high spatial resolution to testing.
This SBIR phase I project focused on developing a screening method based on PFC ISEs to rapidly and directly provide “Yes” or “No” answer for PFC contamination of soils. The developed screening method can be used in field with easy operation and low cost that cannot be performed with current LC/MS/MS technology.
The results of the Phase I project are the following:
- Unified Science LLC has fabricated and characterized the PFOS– ion-selective electrodes. The company has shown that the developed PFOS– sensors can be used to detect PFOS– in water or methanol.
- The company has assessed the effects of co-contaminants in the soil-water slurries. The results indicated that interference from contaminants is insignificant so that the developed PFOS– sensors can be used to directly measure unbound PFOS– in soil-water slurries.
- The company has assessed the effects of co-contaminants in organic extraction supernatant. The results indicated that interference from contaminants is insignificant so that the developed PFOS– sensors can be used to directly to measure total PFOS– in soil samples.
- The company has assessed different extraction methods for measurement of total PFC in soil using the proposed ISE sensor and found out that the most sufficient and easy method is extraction with 50 percent methanol in water.
- The company has developed field PFOS– soil extraction method using boiling water bath. Approximately 100 percent recovery was achieved with this method for soil samples with different PFOS– contamination levels, indicating that the extraction method with boiling water bath is sufficient and reproducible.
- The company has performed blind sample experiments with our developed PFOS– sensor and the boiling water bath extraction method. Recovery of 99 percent was achieved, and no false positive or false negative was found. The results validated our prescreening method for PFOS– contaminated soil samples.
- The company has assessed the developed field PFOS– soil extraction method to extract PFOS– from different soil samples. The results indicate that there is no universal recovery method for different types of soils. To solve this problem, we will develop a method to categorize different soil types and develop suitable extraction methods for each types of soil samples in Phase II.
Unified Science LLC has established and validated a field deployable screening method based on PFC ISEs to rapidly and directly provide “Yes” or “No” answer for PFC contamination of soils.