Presentation on theme: "Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements"— Presentation transcript:
1Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements AIHce 2011Heidi Hayes, Technical DirectorRobert Mitzel, Vice-PresidentBusiness Development1201
2Outline Introduction Study Objectives Sampler Selection Field Sampling ResultsConclusions
3Conventional Air Sampling Summa CanistersPumped Sorbent TubesPossible equipment failureRequires experienced field samplerShort duration (~24 hours)Expensive to shipRequires experienced field samplerShort duration (~8 hours)Sorbent type and sample volume selection is critical
4Passive Sampling Practical Advantages Reliable deployment with little training requiredUnobtrusiveInexpensive to shipTechnical AdvantagesCapable of generating trace level RLsLong-term time-integrated measurementsMore representative indoor air concentrations and increased sensitivity are advantageous to health risk assessments.
5Passive Sampling Concepts Measured in labAnalytical Result(µg)1000 mL1L1000 Lm3XXConcentration(µg/m3)Uptake Rate(mL/min)Sampling duration(min)XAvailable in literatureDependent on Sampler GeometryRecorded in the field
6Project Objectives Sample integration of 1 to 7 days Measurement of a wide VOC suitePetroleum and chlorinated compoundsReporting limits comparable to TO-15 SIM (~0.1 µg/m3)Measured concentrations correlate with TO-15
9Field Sampling – Case 1 Indoor air samples collected Duration 3, 4, and/or 7 daysConcurrent deploymentRadiello 130 – CharcoalRadiello 145 – TD SorbentULTRA III – TD sorbent
10ResultsGood comparability was observed when detections on each sampler were sufficiently above their respective reporting limits.
11ResultsULTRA 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.
12ResultsOne 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.
13Field Sampling – Case 2 Indoor air samples collected 13 sites Concurrent TO-15 cans & ULTRA IIIChlorinated solvents,petroleum products1 to 3 day duration
14ResultsStrong correlation between ULTRA III and TO-15 concentrations across 3 orders of magnitude and at concentrations <0.1 µg/m3
15ConclusionsEach 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.
16ConclusionsULTRA 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.