Presentation on theme: "Air Toxics LTD Laboratory Services Since 1989 Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements AIHce 2011 Heidi Hayes, Technical."— Presentation transcript:
Air Toxics LTD Laboratory Services Since 1989 Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements AIHce 2011 Heidi Hayes, Technical Director Robert Mitzel, Vice-President Business Development 1201
Outline Introduction Study Objectives Sampler Selection Field Sampling Results Conclusions
Conventional Air Sampling Possible equipment failure Requires experienced field sampler Short duration (~24 hours) Expensive to ship Requires experienced field sampler Short duration (~8 hours) Sorbent type and sample volume selection is critical Summa CanistersPumped Sorbent Tubes
Passive Sampling Practical Advantages Reliable deployment with little training required Unobtrusive Inexpensive to ship Technical Advantages Capable of generating trace level RLs Long-term time-integrated measurements More representative indoor air concentrations and increased sensitivity are advantageous to health risk assessments.
Passive Sampling Concepts Concentration (µg/m3) Analytical Result (µg) Uptake Rate (mL/min) Sampling duration (min) 1000 mL 1L 1000 L m3 X XX Recorded in the fieldAvailable in literature Dependent on Sampler Geometry Measured in lab
Project Objectives Sample integration of 1 to 7 days Measurement of a wide VOC suite –Petroleum and chlorinated compounds Reporting limits comparable to TO-15 SIM (~0.1 µg/m 3 ) Measured concentrations correlate with TO-15
Field Sampling – Case 1 Indoor air samples collected Duration 3, 4, and/or 7 days Concurrent deployment –Radiello 130 – Charcoal –Radiello 145 – TD Sorbent –ULTRA III – TD sorbent
Results Good comparability was observed when detections on each sampler were sufficiently above their respective reporting limits.
Results ULTRA III = 5-20 times greater sensitivity than the RAD-Charcoal. ULTRA III had validated sampling rates for chlorinated breakdown products whereas RAD-TD required estimated rates. Diffusive adsorption on the RAD-TD sorbent did not behave as predicted for these light VOCs (chloroform, 1,1-DCE) resulting in low bias. Stronger TD sorbent is required for these VOCs.
Results One indoor air location was severely impacted with chlorinated solvents (100 to 10,000 µg/m3) Sampling duration was 3 days. Both Radiello-TD and ULTRA III exceeded capacity & TD-GC/MS. Radiello-Charcoal had a higher capacity, and solvent extraction allowed for easy dilutions.
Field Sampling – Case 2 Indoor air samples collected –13 sites –Concurrent TO-15 cans & ULTRA III –Chlorinated solvents,petroleum products –1 to 3 day duration
Results Strong correlation between ULTRA III and TO-15 concentrations across 3 orders of magnitude and at concentrations <0.1 µg/m 3
Conclusions Each passive sampler evaluated provided quantitative VOC indoor air measurements for TCE and PCE over a period of up to 7 days. The larger surface area of charcoal provided an advantage over TD-sorbents when sampling high concentrations over multiple days.
Conclusions ULTRA III-TD and Radiello-TD provide greater sensitivity than the Radiello- Charcoal over the 1-7 day period. ULTRA III-TD provides a wider range of VOCs than Radiello-TD. ULTRA III has a built-in blank correction allowing for improved accuracy at trace levels.