Nutech 2703 Sample Train Certification for Ethylene Oxide by US EPA Method 327

Abstract

The Nutech 2703 digital automatic air sampling controller with silica-coated canisters for ethylene oxide sampling procedure by EPA Method 327 has been evaluated. The whole sampling train meets the requirements established by EPA Method 327. The sampling train includes a sample inlet with filter, a digital mass flow controller, a pressure sensor, connection tubes, and a silica-coated canister. The sampling train is automatically controlled by battery power and can operate for any sampling time from 1 hour to 7 days. The sampling QC reports provide data showing sampling flow rate and continuous canister pressure readings throughout the sampling period. The sampling train blank and spike recovery tests were successful when analyzed by GC/MS. The results demonstrate that the Nutech 2703-based sampling train meets the qualifications for taking an ambient air sample by EPA Method 327.

Introduction

US EPA published EPA Method 327 in 2023. This method focuses on the testing of ethylene oxide in ambient air down to 10 pptv. It requires certification that all instruments related to the sampling train have a low background level to avoid affecting the test results. This application focuses on the performance of the Nutech 2703-based sampling train. The certification process shows that the Nutech 2703 sampling train is a reliable system for ambient air sampling of very low-level ethylene oxide by Method 327. Some silica-coated canisters are also certified as part of this program.

1. Sampling Train Configuration

• Sampling Controller:
  • Nutech 2703 sampling device with a digitally controlled mass flow controller that can control flow rates from 0.5 ml/min to 50 ml/min.
  • Built-in pressure sensor reading pressure from vacuum to 30 psig.
  • Computer program to read and report the sampling start and stop time, flow rate, and pressure throughout the sampling period.
• Sampling Inlet:
  • A filter and rainproof inlet connected with a 1/4” silica-coated tube.
• Sampling Canisters:
  • Various brands of silica-coated canisters have been evaluated.

2. Blank Supply Gas

Pure nitrogen or zero air.

3. Certification Standards

Commercially available calibration standard at 1.0 ppmv, diluted to 0.01 to 10 ppbv using the Nutech 2208 dilution system with a humidifier.

4. Analysis System Used for Certification

A Nutech 8910/3608 pre-concentration system with a Thermo Scientific Trace 1300/ISQ 7000 GC/MS system was used for this sampling train certification. An application note using the Nutech 8910/3608 system with the Thermo Scientific Trace 1300/ISQ 7000 GC/MS system to analyze ethylene oxide by EPA Method 327 will be published separately.

5. Results and Discussion

5.1 The Sampling Train Blank

Using clean nitrogen gas as the sampling gas, sampling for 24 hours through the sampling train at a flow rate of 3.5 ml/min into a 6-liter certified clean silica-coated canister. The canister with the nitrogen gas was then connected to the analytical system to analyze the concentration of ethylene oxide. The results are listed in the table, showing that the blank results of the two sampling train units all read ND (not detected) and are less than the MDL of 0.015 ppbv.

5.2 The Recovery of the Sample

Using a calibration standard of 100 pptv (0.1 ppbv) and 1.0 ppbv, the standard is connected to the sampling train, and the standard is sampled for 24 hours from the standard canister to the sample canister through the whole sampling train. The samples collected in the canister were then analyzed by the analytical system. Using the standard gas concentration prepared in the source canister as the base concentration and the analytical result concentration of the sample collected through the sampling train, recovery is calculated by simply using the formula: sample/standard * 100%. The results of both concentration levels are listed in the table. The results show the recovery of the ethylene oxide air sample passing through the sampling train is between 90% and 110% at both high and low levels.