Grantee Research Project Results
Final Report: Open Path Analyzer for Accurate, ppt-level Quantification of EtO via Mid-Infrared Cavity Enhanced Spectrometry
EPA Contract Number: 68HERC21C0016Title: Open Path Analyzer for Accurate, ppt-level Quantification of EtO via Mid-Infrared Cavity Enhanced Spectrometry
Investigators: Gupta, Manish
Small Business: Nikira Labs Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2021 through August 31, 2021
Project Amount: $99,699
RFA: Small Business Innovation Research (SBIR) - Phase I (2021) RFA Text | Recipients Lists
Research Category: Urban Air Toxics , Small Business Innovation Research (SBIR) , Heavy Metal Contamination of Soil/Water , SBIR - Air and Climate
Description:
EtO is one of the largest produced petrochemicals in the world, with ~2.9 million metric tons of produced in the United States alone with a commercial value of $3.5B. It is used in a variety of processes, including ethylene glycol production and medical sterilization. Despite its industrial usage, EtO poses several hazards due to its flammability and toxicity.
After an extensive review of the available data, the US Environmental Protection Agency (EPA) has concluded that the “…confidence in the hazard characterization of EtO as ‘carcinogenic to humans’ is high.” Using this data, the EPA has assigned a total cancer unit risk (inhalation unit risk) estimate for EtO of 3.3 × 10-3 μg/m3 (~12 ppt). Using the EPA inhalation unit risk guidelines, a recent (May 2020) revision to the 2003 Miscellaneous Organic Chemical Manufacturing National Emission Standards for Hazardous Air Pollutants found that, at current levels of control, the carcinogenic risk posed by EtO was too high. Thus, the amendment is working to add requirements for EtO emissions from storage tanks, process vents, flares, and equipment leaks in hopes of reducing total EtO emissions by 0.76 tons per year.
Currently, EtO is measured via EPA Method TO-15. Briefly, a discrete air sample is captured in a Summa canister and shipped to a laboratory for analysis. The canister contents are directed through a solid adsorbent which preconcentrates the volatile organic compounds (e.g. EtO) as well as some common air constituents (e.g. CO2). Cryogenic cooling is then used to remove most of the CO2 prior to compound separation via a gas chromatography column. Finally, the EtO concentration is measured via selective ion or scanning mass spectrometry.
Though this method is extensively used and proven, it has several limitations that make it difficult to address emerging EPA need to measure low ppt-levels of EtO. Foremost, EtO is typically characterized by major m/z peaks at 44 and 29, which are confounded by CO2 and co-eluting species (e.g. trans-2-butene, acetaldehyde, and potentially others) respectively. This limitation can be partially overcome by minimizing leaks, using a longer column, and exploiting other m/z peaks at 15, 41 – 43 and 56; however, this reduces the sensitivity of the analysis, making it unable to quantify low levels of EtO.
In addition to sensitivity and cross-interference issues, EPA Method TO-15 requires the acquisition and transport of discrete air samples. Thus, the measurement is not real-time or continuous and may not be representative of actual, average EtO concentrations. Finally, as described above, accurate and sensitive EtO analysis requires extensive infrastructure and expertise, making it more complex and expensive. An ideal solution would provide selective, on-site, ppt-level monitoring in real-time.
In this SBIR effort, Nikira Labs Inc. has successfully utilized mid-infrared, cavity-enhanced tunable diode laser absorption spectrometry to accurately and rapidly quantity trace levels of ethylene oxide in ambient air.
Summary/Accomplishments (Outputs/Outcomes):
In Phase I, Nikira Labs Inc. demonstrated technical feasibility by fabricating a mid-infrared, cavity-enhanced tunable diode laser absorption system to quantify EtO. Subsequent to determining the optical wavelength region using spectral modeling, a Phase I prototype was fabricated to operate near 3066 cm-1. The system consisted of a DFB diode laser operating near 3262 nm coupled into a high-finesse optical cavity in an incoherent fashion. Light transmitting the cavity was focused onto an amplified, thermoelectrically-cooled InAsSb detector. Custom electronics were used to drive the laser and collect the detector signal. The measured spectra were fit to a function that incorporated tabulated parameters, absorption outside the cavity, and a measured EtO basis set. In a closed-path mode, the system provided very linear results from 0 – 909 ppb EtO (R2 ~ 0.9999) with a precision of better than ±0.5 ppb (1s, 15 minutes) and was readily able to discern EtO releases in ambient air. The Phase I prototype was then converted to an open-path geometry where there were no “wetted” materials and no sample handling losses. This open-path system was shown to detect ambient EtO releases with high precision and fast time response (10 seconds).
In Phase II, the analyzer will be improved to meet EPA’s requirements by using a longer effective optical pathlength, larger mirrors, and refined electronics. Preliminary calculations suggest that the Phase II system will achieve a measurement precision of better than 12 ppt. This improved unit will be packaged in a field-deployable enclosure and compared directly to EPA Method TO-15 at a variety of sites. The Phase II instrument will also be used for fenceline monitoring applications to estimate source emissions.
Conclusions:
In addition to its utility for next-generation environmental monitoring, a sensitive, real-time EtO analyzer also has commercial utility in the medical sterilization and petrochemical markets. A preliminary analysis of these markets suggests that Nikira Labs Inc. can realize a 5-year revenue exceeding $7.8M for these two applications alone. During Phase I, Nikira Labs Inc. has already commenced discussions with a major petrochemical producer and analytical instrumentation manufacturer.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Gupta M, Chan AP, Sullivan MN, Gupta RM. Trace Measurements of Ethylene Oxide Using Cavity-enhanced Absorption Spectrometry near 3066 cm–1. Aerosol and Air Quality Research. 2022;22(10):220046. |
68HERC21C0016 (Final) |
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SBIR Phase II:
Open Path Analyzer for Accurate, ppt-level Quantification of EtO via Mid-Infrared Cavity Enhanced Spectrometry | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.