Improved Method for Petroleum Hydrocarbons in Solids
By Mark Hugdahl, Technical Director, ALS Environmental – Canada
Beginning April 1, 2013, the ALS Environmental laboratory in Winnipeg will begin the use of a new and improved analysis method for Petroleum Hydrocarbons in soils and other solids. The Microscale Solvent Extraction (MSE) Technique has been used successfully at other ALS Canada laboratories for almost five years and is now available at ALS Winnipeg as a CALA accredited test procedure.
The MSE method, also known as the “Tumbler” extraction technique, will be used for the analysis of CCME Petroleum Hydrocarbon fractions (F2-F4G) in soils, sediments, sludges, and wastes. The method has been demonstrated to meet all regulatory requirements specified by CCME and all provincial jurisdictions where ALS Canada operates.
What is the MSE Tumbler Technique
The MSE Tumbler technique employs a solvent extraction of a solid sample from within a sealed extraction vessel, using an end-over-end rotator. The process is based on US EPA Method 3570, Microscale Solvent Extraction. The end-overend rotational motion of the rotary extractor in combination with in-situ chemical desiccation provides exceptional soil dispersion, promoting maximum contact between dried soil particles and the extraction solvent. This provides a highly efficient extraction of petroleum hydrocarbons, even from complex sample matrices such as clays, peats, and sludges.
Regulatory Acceptance and Equivalency
The new method has been extensively tested for compliance with the CCME Petroleum Hydrocarbon Tier 1 method requirements.
ALS has conducted thorough validation and equivalence testing on this method using a variety of petroleum-contaminated samples and reference materials, with comparison against the CCME reference method (16-hour Soxhlet extraction). All CCME equivalence requirements were met, and all data quality objectives that form part of ALS Environmental’s quality management program were exceeded.
All ALS Canada laboratories that offer this method regularly demonstrate proficiency through comprehensive Quality Control practices, and by participation in CALA’s biannual Proficiency Test (PT) program.
New Standard Detection Limits
TThe new method employs slightly higher detection limits than have been used previously at ALS Winnipeg. Detection Limits (DLs) have been raised in response to client concerns about low level positive results due to the extraction of naturally occurring organic matter that is commonly found in many soil types. In all cases, our new DLs are more than five times below the lowest CCME Tier 1 guidelines.
|CWS Fraction||New DL||Lowest CCME Tier 1 Levels (2012)|
|F2||25 mg/kg||150 mg/kg|
|F3||50 mg/kg||300 mg/kg|
|F4||50 mg/kg||2800 mg/kg|
|F4G||500 mg/kg||2800 mg/kg|
The ALS MSE tumbler technique will provide our clients with reduced turn-around-times, and with improved precision and accuracy for CCME PHC tests.
Recovery of the relatively volatile F2 (C10-16) fraction is greatly improved with this method because evaporative losses are virtually eliminated with this technique.
Additionally, this method is less susceptible than the Soxhlet or Soxtec methods to false positive results in the F3 range, which can be caused by exhaustive extraction of natural organic material from soil types with very high organic carbon content (e.g. peat/muskeg, humic material, wood wastes, etc.).
Within the laboratory, the tumbler extraction technique minimizes solvent usage, health and safety issues, and the generation of wastes, which is consistent with the ALS program of pollution prevention and environmental stewardship. The plots shown at right summarize equivalence study data taken from five different ALS Canada laboratories, comparing results between the MSE Tumbler method and the Soxhlet reference method. The average relative percent differences (RPDs) between the two methods were less than 2% for all three hydrocarbon fractions (F2, F3, F4).
Beginning April 1, 2013, ALS Winnipeg will utilize MSE Tumbler extraction as the primary test method for the analysis of CCME F2-F4G parameters in solids. We will continue to offer our Soxtec method by special request. For further information please contact ALS Environmental at 204-255-9720 or toll free 1-800-668-9878.