Evaluation of sample collection containers for selenium quantification

Naturally occurring concentrations of selenium (Se) are very low: 0.02 µg L-1 in freshwater and 0.01-2 mg kg-1 in soil.  Mining operations must discharge water in accordance with the United States Environmental Protection Agency’s established maximum contaminant level and may be required to discharge at even lower limits set by the state.  For accurate analysis, sample collection containers and labware must be carefully chosen to prevent changes in composition through interactions between sample and container.  Our objective was to assess four materials (glass, silanized glass, polytetrafluoroethylene, and polypropylene) for use in Se quantification.  Varying Se stock solutions (0, 10, 25, and 50 µg L-1) were prepared in 0.1 M sodium chloride, delivered to each container, and equilibrated for 6, 12, 24, or 48 hours.  Selenium was lost to all containers with the least loss occurring in the silanized-treated glass (1-12% across all concentrations).  Silanized glassware is recommended for Se quantification as it improved sample integrity.