Method Holding Times & Preservation

Apr 1

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4/1/2007 4:00 AM  RssIcon

General Sample preservation temperature requirement has changed from 4 (+/- 2) degrees C to less than or equal to (=<) 6 degrees C. Hexavalent Chromium - The Rule includes the extension of the holding time when analyzed by the Ion Chromatography method EPA 218.6 from 24 hours to 28 days. The sample must be pre- served at the time of sampling with the ammonium sulfate buffer solution specified in the method. Note: the holding time for EPA 7199 remains at 24 hours. For metals other than boron, hexavalent chromium, and mercury, EPA will allow sample preservation with nitric acid 24 hours prior to analysis. In other words, acid preservation in the field for metals is not required. However, sample preservation status should be clearly labeled so that the laboratory can determine if acidification is required before analysis. Unstable analytes such as chlorine, pH, dissolved oxygen must be analyzed in the field to meet the 15 minute EPA specified holding time or will be flagged as received & analyzed outside of this specification. Orthophosphate must be field filtered within 15 minutes of sampling and anayzed within 48 hours.

As always, please contact your Laboratory Project Manager with any questions regarding your permit’s sampling & analytical plan requirements.

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