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    Oil and Grease

    March 27, 2009 | Posted by WETLAB

    Oil & Grease

    Method: EPA 1664
    Volume: 1L for RL = 1.5mg/l, 2L for RL = 1.0mg/l
    Preservation: HCl, 2-6 degrees C, Amber glass bottle
    Special Requirements: for every set of samples submitted (1 to 20 samples) a duplicate sample must be submitted for internal laboratory QA/QC requirements. The client is not charged for this duplicate sample.

    Western Environmental Testing Lab carries certification in NV and CA for the analysis of water samples for oil and grease by method EPA1664. WETLAB utilizes the “Solid Phase Extraction” or SPE technique. This method is used for determining n-hexane extractable material (HEM) which includes some non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and related materials.

    In order to perform the oil and grease analysis we filter the client sample through a specially prepared filter that has the ability to hold onto oils and greases. Once the sample has been filtered through, we extract from the filter all the oil and grease using three portions on n-hexane. The n-hexane extracts are combined in a pre-weighed tin and evaporated. Once all the n-hexane is evaporated what is left is any oil and grease from the original sample. We determine the amount of oil and grease by comparing the final weight of the tin to the original weight. This is known as a gravimetric determination.

    There are two very important requirements of the method that the client needs to be aware of concerning Oil & Grease. The first is that the client must collect the sample in a 1-liter glass container. Plastic does not work since it is more susceptible to oils and greases sticking to the inside of the container. The second requirement is that the lab must analyze a second 1-liter sample (one for every 20 samples analyzed) as part of the QA/QC requirements of the method. This is an issue since we usually only receive one sample per site from the client. We generally send out an extra 1-liter sample container per bottle kit to the clients that is labeled as a QA/QC sample (or "Duplicate"). This sample is not actually used as a laboratory duplicate and should not replace any field duplicates required by your sampling protocols, it is simply used to provide additional sample volume to run the method required QA/QC. Please remember we do not charge the client for this extra sample, it is simply a sample that we need to satisfy all method requirements.

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