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Question/Answer

When treating this product with only hexanes, such that I am only extracting nonpolar components, should my reference value be 20mg? This would be because only the hexadecane is being extracted.

Hexane will extract both hexadecane and stearic acid. Your final result should be 40 mg extracted from this standard. Even though the carboxylic acid functional group adds a certain amount of polarity to the end of the chain, the non-polar carbon chain allows for solubility in organic solvents. If you use the silica gel treatment (SGT-HEM) prior to evaporation of hexane, that will give you selectivity between the stearic acid and hexadecane, with a final result of 20 mg.

Do I need to extract the stearic acid as well as hexadecane in order to achieve 100% recovery?

To comply with EPA method 1664 you must use the a standard with 20 mg hexadecane and 20 mg stearic acid, which gives 40 mg total HEM. The total recovered amount must be in the range of 83-101% for the initial precision and recovery standard or 78-114% for the ongoing precision and recovery standard.

What is the acceptable range for only the SGT-HEM portion of this standard (G3025)?

The method defines an acceptable range of SGT-HEM recovery as 83-116% for the initial precision and recovery (IPR) and 64-132% for matrix spikes and ongoing precision and recovery.

Is this product ISO 34 Certified?

Yes, these products carry guide 34 certification.

Is this product ISO 34 Certified?

This standard is made by a Guide 34 certified manufacturer. Please see http://www.envexp.com/coa for a sample COA for this product. Cycle through to the end of the listing to see the most current COA with ISO certification references.

If I use half the volume into 1L will I get back 20mg/L

That would be correct but it is not recommended to treat this standard in that manner - it should be used as a whole volume.

If I use the 40mg HEM standard for the Silica Gel portion for TPH only, should my reference value be 20mg?

Yes, the standard is 20 mg stearic acid and 20 mg hexadecane.

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