Soil Vapour Forum- Charcoal Tubes and Miscellaneous Sampling Methods - PowerPoint PPT Presentation

ANALYTICAL CHEMISTRY & TESTING SERVICES Soil Vapour Forum- Charcoal Tubes and Miscellaneous Sampling Methods Right solutions…. presented by Kari Mulroy ….Right partner

ANALYTICAL CHEMISTRY & TESTING SERVICES Charcoal Tubes

Charcoal Tubes • Active sampling with mechanical pumps - 15 minutes to 8 hours typical - Flow rate can vary, typically 200mL/min • Sample time and flow rate dependant on compound and method selection - OSHA/NIOSH methods provide guidelines - Following these guidelines helps prevent breakthrough problems & over saturation - Modifications to reference methods must be validated

Charcoal Tubes • Charcoal extracted/desorbed in solvent – Commonly carbon disulfide (CS 2 ) but chosen according to compound of interest and method being run, i.e. NIOSH/OSHA methods – 1-2 µ L injected into GC/FID or GCMS – 1/500 th to 1/1000 th of total sample analyzed

Charcoal Tubes • DL & Sampling Volume Considerations – DLs are dependant on total sampling volume (sampling time x flowrate). – Typical detection limits for discretes: • 1 ppmv for 15 minutes x 100 mL/min • 0.05 ppmv for 8 hours x 100 mL/min • Lower DLs achievable by GCMS – Upper limits dependant on breakthrough volume and charcoal tube capacity • Lighter hydrocarbons breakthrough earlier • Upper limit ~10,000ppmv for 15 minutes x 100 mL/min, or ~200 ppmv for 8 hours x 100 mL/min

Charcoal Tubes • Advantages – Reanalysis of samples is possible • Facilitates dilutions for high samples • Confirmation by alternate detector possible – Easily transported – “Back” tube sampled for every sample • Breakthrough checks always possible – Moisture is not typically a problem – Tubes and pumps are readily available – Sample stability ( ≥ 14 days) – Control capacity / max sampling volume by tube size selection – Lower cost method

Charcoal Tubes • Disadvantages – Less sensitive than some of other methods – Require higher sampling volume – Shorter list of applicable compounds than TO15/17 – Requires a pump in the field – Note: Speak to the lab about DL requirements. When applying potential attenuation factors charcoal may be appropriate.

Miscellaneous Tubes - XAD

Miscellaneous Tubes - XAD • PAHs may be sampled on XAD tubes using NIOSH methods. • Achievable DLs vary with sampling volume. • Same advantages / disadvantages as charcoal method.

Miscellaneous Tubes - DNPH

Miscellaneous Tubes - DNPH • Acetaldehyde and acrolein can be collected on DNPH tubes. • Analyzed by NIOSH 2018 or EPA TO-11 • Both methods require HPLC analysis and typically have a DL of 0.5ug per tube. • Acrolein can be unstable on this media.

Miscellaneous Media – Filter Cassettes / XAD / Silica Gel

Miscellaneous Media – Treated Filters • Filter cassettes maybe used to collect some compounds such as chlorine • Treated filter, analyzed by NIOSH 6011 • Disadvantages: • Large air volume and flowrate required • Media is less readily available

Miscellaneous Media – Impingers / Bubblers

Miscellaneous Media – Impingers / Bubblers • Bubblers can be used as an alternate media for some substances: • Acrolein can be collected by a modified CARB 430 which uses toluene in the bubbler to extract the reacted acrolein away from the DNPH solution. • Hydrogen Cyanide may be collected using a bubbler, following NIOSH S288 • Alternate method is NIOSH 7904 (soda lime tube)

Miscellaneous Media – Impingers / Bubblers • Advantages*: • Typically used only where necessary • Disadvantages: • Equipment is fragile • Handling chemical solutions in the field • TDG issues * In some cases, may be the only option to meet required detection limits.

Questions?