ASTM D4281 Standard Test Method for Oil and Grease (Fluorocarbon Extractable Substances) by Gravimetric Determination
6. Purity of Reagents
6.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean Type IV reagent water conforming to Specification D1193.
7. Sampling
7.1 Collect the samples in accordance with Specification D1192 or Practices D3370, when applicable.
7.2 Collect grab samples only directly into the sample bottle. Oils and greases may be lost on any sampling equipment used. Do not rinse the sample bottles with the sample prior to filling as the oils may adhere to the inside of the bottle and lead to high results.
7.3 Because a portion of the collected oils and greases may adhere to the sample bottle, analyze all of the sample collected as one specimen. One-litre samples are normally specified, although larger or smaller samples may be taken depending on the concentration of extractables expected to be present.
7.4 Leave an air space above the liquid in the sample bottle to facilitate handling during analysis.
7.5 Collect all samples in glass bottles with nonorganic or insoluble caps, or both.
7.6 Acidify the sample to < pH 2 with HCl (1 + 1) or H2SO4(1 + 1) to maintain the integrity of the sample.
NOTE 2 - For Clean Water Act purposes only H2SO4 should be used and the sample should be cooled to 4°C and analyzed within 28 days.
