Open Path Analyzer for Accurate, ppt-level Quantification of EtO via Mid-Infrared Cavity Enhanced Spectrometry

In this Small Business Innovation Research effort, Nikira Labs Inc. proposes to develop a sensitive (<10ppt), real-time, and highly-selective ethylene oxide (EtO) analyzer suitable for field-deployment. The US EPA has concluded that EtO, which is widely used in ethylene glycol production and medical sterilization, is carcinogenic to humans and assigned it a total inhalation unit risk of 3.3 x 10-3 �g/m3 (~12ppt). At current levels of control, the carcinogenic risk of EtO is too high, and new amendments to the 2003 Miscellaneous Organic Chemical Manufacturing National Emission Standards for Hazardous Air Pollutants will most likely require significantly improved EtO monitoring. Current monitoring techniques (EPA Method TO-15A) only provide infrequent, single measurements (grab samples) and may be confounded by interfering compounds. In Phase I, Nikira Labs demonstrated technical feasibility by fabricating a mid-infrared, cavity-enhanced tunable diode laser absorption system to quantify EtO. 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. 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. (1(std), 15 minutes) and was readily able to discern EtO releases in ambient air. The 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, Nikira Labs will extend the work to develop, fabricate, test, deploy, and deliver two EtO monitors. The first will use cavity-enhanced absorption spectroscopy with a longer effective optical pathlength, larger mirrors, and refined electronics to achieve a measurement precision of better than 12 ppt. This analyzer will be field-deployed and compared directly to EPA Method TO-15 at a variety of sites. A second instrument will utilize open-path tunable diode laser absorption spectroscopy to make perform fence line monitoring of EtO near potential sources. 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. Letters of support have been provided by prominent petrochemical companies.