Simultaneous Sampling of Selenium and Mercury

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Simultaneous Sampling of Selenium and Mercury

• Nathan Darnall
• U.S. fish and Wildlife Service
• August 29, 2005

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Sample Collection

• Equipment (e.g., boat, screens, nets)
• Maintenance (e.g., motor) (prop, gas)
• Staff time (training, preparation, collection,
  processing)
• Sampling equipment (e.g., chemically clean jars,
  gloves, nitric acid)
• Storage and Shipping

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Analytical Costs (separate)

• Full metals scan 301
• (includes prep and determination)
• Selenium via Graphite Furnace (HGA)
• Sample prep 51
• Se determination 41
• Mercury via Cold Vapor (CV)
• Sample prep 51
• Hg determination 34

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Analytical Costs (combined)

• Sample preparation 51
• Selenium determination 41
• Mercury determination 34
• Incremental cost of only 40
• FWS contract prices about 30 lower

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Sample Preparation Storage

• Sample homogenized and freeze dried
• Aliquots (a small sub-sample)
• An aliquot can be frozen for later analysis
• stored up to 1 year, generally 6 months
• considerations storage space, power outage

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Summary

• Costs associated with sample collection are
  substantial
• Hg and Se in tissue samples measured in ppm, so
  no special techniques needed
• Minimal extra cost per sample for Hg analysis
• Samples can be analyzed at the same time, or
  stored for up to one year