The following guidelines are taken from "Standard Methods for the Examination of Water and Wastewater", 19th Ed., 1995, A.D. Eaton, L.S. Clesceri, and A.E. Greenberg, ed.

• Rinse container 2-3 times with the sample to be collected
• fill the container full, leaving approximately 1% of the volume empty to allow for possible thermal expansion
• determine how much concentrated nitric acid is required to bring the sample to a pH < 2 on a separate sample first
• use the same bottle of acid throughout the analysis in order to obtain a reliable blank
• if sampling a stream, collect the sample at mid-stream and at mid-depth
• use a sample bottle with a polytetrafluoroethylene (TFE or Teflon) liner

2. Sample Containers

• Sample containers should be composed of quartz or tetrafluoroethylene (Teflon). Cheaper alternatives are composed of polypropylene or linear polyethylene with a polyethylene cap. Borosilicate glass can be used, but avoid "soft glass" containers if the sample concentration is in the microgram/L range (ppb).
• Containers and filters need to be cleansed as follows. Thoroughly clean the sample containers with a metal-free non-ionic detergent solution, rinse with tap water, soak in acid, and then rinse with metal-free water. For quartz, TFE, or glass materials, use 1+1 HNO₃, 1+1 HCl, or aqua regia (3 parts conc. HCl + 1 part conc. HNO₃) for soaking. For plastic material, use 1+1 HNO₃ or 1+1 HCl. Reliable soaking conditions are 24 hr at 70 ^oC.

• Acidify immediately after sampling with concentrated nitric acid to a pH < 2 (usually 1.5 mL conc HNO₃ /L sample). High purity commercial acid such as provided by J.T. Baker is preferred.
• After acidification, refrigerate at 4 ^oC. Samples with metal concentrations in the ppm range will stay stable for up to 6 months; concentrations in the ppb range need to be sampled as soon as possible.

Direct suggestions, comments, and questions about this page to Pete Poston, postonp@wou.edu

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