Description_x000D_ General description_x000D_ This proficiency testing sample is produced in accordance with ISO/IEC 17043:2010. All information regarding the use of this material can be found in the reporting packet supplied for each sample._x000D_ Preparation Note_x000D_ This PT sample is packaged as a 20 mL concentrate. The solvent for this sample is water. The PT sample has been autoclaved for preservation._x000D_ Sample Preparation_x000D_ To prepare solution, partially fill a 1L volumetric flask with reagent-grade water._x000D_ Open ampule PE1130-20ML (be careful to avoid cuts on glass) and transfer 10mL from the ampule into the flask._x000D_ Fill the volumetric flask to volume with reagent-grade water and mix well._x000D_ The sample is now ready for immediate analysis._x000D_ Analyze the solution to determine BOD or CBOD first. If COD and TOC cannot be determined within two hours after sample preparation, an aliquot should be preserved (pH<2) using 0.2 mL of concentrated sulfuric acid per 100 mL. This aliquot should be stored at 4 degrees Celsius and analyzed as soon as possible within the 28-day maximum holding time._x000D_ Note - For proper oxygen depletion of BOD and CBOD, the sample should be tested in a dilution series. Use a natural surface water or diluted domestic sewage for seeded dilution water and avoid entrainment of air. For analysis of CBOD, the use of a nitrifying inhibitor is recommended. Be sure to determine the “blank” BOD of your seeded dilution water so that the proper seed correction can be made._x000D_ Other Notes_x000D_ Proficiency testing samples are presented as single blind. No values for the samples are released until the testing period concludes. Values of analytes vary lot to lot._x000D_ Proficiency Testing Schedule (2020-2021)_x000D_ Wastewater_x000D_ WP20-1 January 15 - February 28, 2020_x000D_ WP20-2 March 25 - May 8, 2020_x000D_ WP20-3A May 13 - June 26, 2020_x000D_ WP20-3B July 8 - August 21, 2020_x000D_ WP20-4 September 23 - November 6, 2020_x000D_ WP20-5 November 25 - January 8, 2021_x000D_ WP21-1 January 13 - February 26, 2021_x000D_ WP21-2 March 24 - May 7, 2021_x000D_ WP21-3 July 7 - August 20, 2021_x000D_ WP21-4 September 22 - November 5, 2021_x000D_ Quick-Turn Study - (non-scheduled proficiency test that is available at any time)