Storage Stability of 66 Volatile Organic Compounds (VOCs) in Silicon-Lined Air Canisters for 30 Days

Importance of the Topic

Proper collection and storage of volatile organic compounds is essential for accurate environmental monitoring and regulatory compliance. VOCs contribute to air pollution, impact human health and the environment, and are regulated by EPA methods. Ensuring sample integrity during transport and storage prevents analytical bias and supports reliable decision making.

Objectives and Study Overview

This study evaluated storage stability of 66 VOCs defined by EPA Method TO-15 in two commercially available silicon lined 6 liter air canisters over a 30 day period. Experiments under dry (0% RH) and humid (93% RH) conditions compared recoveries and stability. Two canister types from different vendors were assessed for statistical differences in analyte retention over time.

Methodology

Six canisters of each type were cleaned per TO-15 procedures, spiked to 5 ppbv of a 65 component TO-15 mix, and pressurized to 30 psig with nitrogen at specified humidity levels. Samples were analyzed on Day 0 and Day 30 using cryogenic preconcentration and GC-MS quantitation. Recovery was defined as measured concentration relative to spike. Stability criteria followed TO-15 audit accuracy of ±30 percent change over 30 days.

Used Instrumentation

• Cryogenic Nutech 8900DS preconcentrator with three traps including Tenax and water removal stage
• Agilent 6890 gas chromatograph coupled to Agilent 5973 mass selective detector
• Rtx VMS GC column 30 m x 0.25 mm ID x 1.4 μm film for separation

Main Results and Discussion

Under dry conditions both canister types showed mean recovery near 100 percent with no significant difference after 30 days. Sixty four of 66 compounds remained within ±30 percent change. In humid conditions mean recoveries declined to 85-88 percent with acrolein, dibromochloromethane and bromoform unstable in both canister types. Only acrolein showed a significant vendor difference under humid storage. Calibration differences and water dissolution effects accounted for most anomalies.

Benefits and Practical Applications

• Demonstrates robust storage performance of silicon lined canisters for most VOCs over 30 days
• Supports field sampling programs requiring extended holding times
• Guides selection of canister types for environmental and industrial air monitoring

Future Trends and Potential Applications

• Expand studies to larger and aged canister populations for real world conditions
• Assess storage in alternative gases such as ambient air to simulate field environments
• Investigate additional VOC classes and lower detection levels
• Develop calibration protocols to minimize standard aging effects

Conclusion

This comparison confirms that commercially available silicon lined canisters yield equivalent storage stability for the majority of EPA TO-15 VOCs under both dry and humid conditions. A small subset of water soluble compounds may degrade under high humidity. Proper calibration and sample handling remain critical for accurate analysis over extended holding times.

References

• U S Environmental Protection Agency Compendium Method TO-14A Determination of Volatile Organic Compounds in Ambient Air Using Specially Prepared Canisters With Subsequent Analysis by Gas Chromatography 1999
• U S Environmental Protection Agency Compendium Method TO-15 Determination of Volatile Organic Compounds in Air Collected in Specially Prepared Canisters and Analyzed by Gas Chromatography Mass Spectrometry 1999
• Herrington JS Rapid Determination of TO-15 Volatile Organic Compounds in Air Application Note EVAN1725A-UNV Restek Corporation 2012
• Westberg HH Holdren MW Hill HH Analytical Methodology for Identification and Quantification of Vapor Phase Organic Pollutants Washington State University 1981
• Holdren MW Rust S Smith R Koetz J Evaluation of Cryogenic Trapping for Collecting Organic Compounds in Ambient Air Final Report US Environmental Protection Agency 1984
• Oliver KD Pleil JD McClenny WA Sample Integrity of Trace Level VOCs in Ambient Air Stored in SUMMA Canisters Atmospheric Environment 20 1986
• Gholson AR Storm JF Jayanty RK Fuerst RG Logan TJ Midgett MR Evaluation of Canisters for Measuring Emissions of VOCs from Hazardous Waste Incineration JAPCA 39 1989
• Jayanty RKM Evaluation of Sampling and Analytical Methods for Monitoring Toxic Organics in Air Atmospheric Environment 23 1989
• Holdren MW Matthews MC Orban JE Smith DL Stability of VOCs in SUMMA Polished Canisters Battelle Columbus Ohio 1991
• Parmar SS Study of Holding Times for H2S COS and CH3SH Gas Phase Samples in Different Containers Proc 1991 EPA AWMA Symposium 1991
• Merrill RG Zapkin MA Application of Canister Sampling to Volatile Polar Organic Compounds VIP-21 1991
• Oliver KD Sample Integrity of Polar VOCs in Ambient Air Stored in SUMMA Polished Canisters Technical Note TN-4420-93-03 ManTech Environmental 1993
• Kelly TJ Callahan PJ Pleil JD Evans GF Field Measurements for Polar VOCs in Ambient Air Environ Sci Technol 1993
• Holdren MW Skarpness BO Strauss WJ Keigley GW Effectiveness of Silcosteel Treatment of Canisters Unpublished Report 1994
• Brymer DA Ogle LD Jones CJ Lewis DL Viability of SUMMA Polished Canisters for VOC Collection Environmental Science and Technology 30 1995
• Sin DW Wong YC Sham WC Wang D Stability of 143 VOCs in SUMMA Canisters by GC-MS Analyst 126 2001
• Pate B Jayanty RKM Peterson MR Evans GF Temporal Stability of Polar Organic Compounds in Stainless Steel Canisters J Air Waste Manag Assoc 42 1992
• Gholson AR Jayanty RKM Storm JF Evaluation of Aluminum Canisters for Air Toxics Analysis Anal Chem 62 1990
• Kelly TJ Holdren MW Applicability of Canisters for Sample Storage in Hazardous Air Pollutants Determination Atmospheric Environment 29 1995
• Hasegawa A Examination of Storage Stability of Chemical Substances in Atmosphere Sampling Canister Journal of Environmental Chemistry 11 2001
• Ochiai N Tsuji A Nakamura N Daishima S Cardin DB Stabilities of VOCs in Fused Silica Lined and SUMMA Canisters Under Various Humid Conditions Journal of Environmental Monitoring 4 2002
• Hsieh CC Horng SH Liao PN Stability of Trace Level VOCs Stored in Canisters and Tedlar Bags Aerosol and Air Quality Research 3 2003