Controlled Generation of Peracetic Acid Atmospheres for the Evaluation of Chemical Samplers

Introduction

The goal of the experimental design and research presented herein was to produce peracetic acid (PAA) atmospheres suitable for evaluating PAA sampling methods in a controlled environment. To achieve this, generated test atmospheres must: enable simultaneous exposure of multiple samplers to equivalent atmospheres; maintain a continuous stable atmosphere for a duration to exceed experimental time frames; and produce a range of analyte concentrations, air velocities, temperatures and humidities. The American Conference of Governmental Industrial Hygienists (AGCIH) Threshold Limit Value (TLV) for PAA is 0.4 ppm. The goal was to generate PAA atmospheres with concentrations from one tenth of the TLV up to 100 times the TLV.

PAA is a reactive chemical, which presents some inherent challenges to generation of standard reference materials and atmospheres. PAA is a strong oxidant. PAA solutions are labile, thus it is difficult to keep reference standards or atmospheres. In solution, PAA and water are in equilibrium with acetic acid (AA) and hydrogen peroxide (HP). The equilibrium shifts as solutions of PAA evolve oxygen gas through the degradation of HP. Dynamic PAA atmospheres which are flowing and continuously refreshed are the preferred method for exposing samplers to equivalent atmospheres. Generation of static atmospheres by evaporating PAA solution into a closed container cannot be maintained for very long before needing to be refreshed. Dynamically generated atmospheres are created by a continuously renewed flow of air as a carrier and a source of PAA vapors, which are necessary for evaluating sensor performance over time frames relevant to occupational safety.

Generation of PAA vapors can be accomplished from assisted vaporization, including applying heat and/or aerosolization with a nebulizer to accelerate evaporation. Glass reacts with PAA to hydroxylate the silica. used a glass syringe to deliver PAA solution to a nebulizer; however, gas bubbles formed in the syringe leading to uncontrollable ejection of the PAA solution from the syringe. To mitigate this, used acid washed syringes. They generated atmospheres of up to 2 ppm with a reported 95% recovery of theoretical delivered PAA. Dilute solutions of PAA can help to mitigate gas evolution but require more energy to evaporate and introduce additional humidity.

For these experiments, PAA vapors were swept directly from the headspace above a PAA solution into our generation system. The flow rate of the air sweeping the headspace was varied to achieve the desired concentration after dilution into the carrier gas stream. When evaporating diluted PAA solutions using a nebulizer, the minimum humidity range is limited due to the water content in the dilute PAA solution. Thus, a wider humidity range on the low end is available when sweeping the headspace. The ability to maintain the concentration of PAA in the headspace above the solution is limited by the kinetics at the PAA solution-air interface. A practical solution was achieved using a PAA delivery system where air was passed through the headspace above a PAA solution in a vial. An impinger with a N,N-diethyl-p-phenylenediamine (DPD) analysis was used as the reference measurement for the PAA concentrations in the generated atmospheres.

Data Collection Methods

1. Chamber and Sensors
   • Model 501, Miller-Nelson Instruments, Flow Temp Humidity Control System (Assay Technologies, Livermore, CA).
   • Environmental chamber from Darwin Chambers Company (St. Louis, MO).
   • Model 4043 Flow meter from TSI Incorporated (Shoreview, MN).
   • Temperature and humidity sensor / recorder from Onset Corp (Bourne, MA).
   • Custom glass mixing chamber from Kontes Kimble-Chase Glass (Vineland, NJ).
   • Sample manifold and glass columns from Ace Glass (Vineland, NJ).
   • PAA sensor SafeCide™ Portable Monitoring was from ChemDAQ Incorporated (Pittsburgh, PA).
2. Impinger Sampling
   • Water deionized to > 18 MΩ-cm using an Evoqua Water Technologies (Pittsburgh, PA) water purification system.
   • PAA solution (32% w/w of PAA, 40-45% w/w of acetic acid, and <6% w/w of H₂O₂) was supplied by Sigma Aldrich (USA).
   • A V-2000 photometer and PAA Vacu-vials® instrumental test kits (K-7913) were purchased from Chemetrics.
   • 50-mL glass impingers were purchased from Ace Glass (NJ, USA).

Publications

Doepke A, Stastny AL, Streicher RP. Controlled generation of peracetic acid atmospheres for the evaluation of chemical samplers. Anal Methods. 2021 Sep 2;13(34):3799-3805. doi: 10.1039/d1ay00958c.

Acknowledgements

Amos Doepke ADoepke@cdc.gov
Angela L. Stastny AStastny@cdc.gov
Robert P. Streicher RStreicher@cdc.gov

Funding

Funding was provided through NIOSH CAN 93908S6

Contact

For further information contact:
Chemical and Biochemical Monitoring Branch (CBMB),
Health Effects Laboratory Division (HELD),
National Institute for Occupational Safety and Health (NIOSH),
Cincinnati, OH
513.841.4414