Analysis of Extract Drying Criteria for Oil & Grease Method 1664A/B

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US EPA Method 1664 for Hexane Extractable Material (HEM) or Oil & Grease has allowed use of solid phase extraction (SPE) instead of liquid-liquid extraction (LLE) with hexane since 2007 and this has been widely adopted in the US. SPE is an equivalent extraction technique to LLE and produces the same n-hexane extract. The extract, similar to LLE, may contain residual water that must be treated properly and removed from the n-hexane extract.
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In February of 2010, the US EPA released EPA Method 1664B. One of the allowable modifications 1.7.1.12 is the use of solvent phase separation paper or other equivalent means may be used instead of sodium sulfate to remove water from the extract provided all QC requirements are met especially Sections