Extractable Petroleum Hydrocarbon (EPH) – Extractable Background of Resprep EPH Cartridges

Restek’s Resprep EPH Fractionation SPE Cartridges (cat # 25859) provide method-specific performance for EPH analysis of soil and water samples through complete separation of aliphatic and aromatic compounds into distinct fractions, while providing extractable background levels guaranteed to fall under the strict reporting limits of Massachusetts and New Jersey EPH methods.


The cleanliness of silica gel cartridges is critical for EPH analysis. Like many methods, this method is subject to false positives and false negatives when reporting target PAH analytes. Non-targeted hydrocarbons can elute or co-elute within the targeted retention time window, which may lead to falsely identifying or quantifying target analytes. Also, the ability to identify or quantify low concentration target analytes may be inhibited if large, unresolved complex matrices are present beyond the cleanup capacity of the method.


In addition to matrix concerns, plasticizers and other compounds can leach from commercially available silica gel cartridges and should be monitored during each analytical batch analysis. The MA EPH and NJ EPH methods specify a procedure involving dichloromethane during the conditioning step followed by an abundant amount of hexane to eliminate or minimize leaching contamination. However, by using this procedure, the amount of solvent used is significantly increased and there is a concern of dichloromethane remaining in the silica gel bed during the aliphatic elution, which could lead to breakthrough issues. Laboratories must report the presence of any contamination leaching from the cartridges within the C11 – C22 aromatics range.


Restek guarantees a background level in each fraction, aliphatic and aromatic, of less than half the strict reporting limits of MA EPH and NJ EPH methods. The figure below shows the extractable background from C9 – C18 and C19 – C36 in the aliphatic fraction and C9 – C16 and C16 – C36 of the aromatic fraction. The extracted background in region 2 of both fractions has the area of the surrogate peaks removed.


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