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         Microwave Digestion

Method information

We have some standardized methods for plant, soil and water samples.  For other material, we develop a method to achieve complete digestion.  We generally try to digest the maximum sample weight in the smallest extraction volume to achieve a concentrated digest solution.

Typical method parameters:

Small sample size:

  • powdered samples facilitate digestion
  • maximum 250 mg for organic samples (e.g. plants, animal tissue)
  • maximum 500 mg for inorganic samples (e.g. soils)

Extraction volume: minimum 5 ml, typically 10 ml

Acid solution: typically nitric acid, hydrochloric acid, aqua regia or acid+water

Temperature: typically 180 ºC - 200 ºC depending upon sample type

Duration: ramp to temperature, holding and cool down can take 30-60 minutes depending upon selected program

Sample capacity per batch: minimum 6 and maximum 40 including blanks

Pre-digestion:  highly reactive samples require pre-digestion for anywhere from 15 minutes to overnight

Filtration: in some cases filtration is required after digestion (usually soil samples)

Precautions

  • Because we do not use hydrofluoric acid in our lab, silicates may not be completely dissolved.
  • Because nitric acid is reactive with organic material, the nature of the sample must be known prior to digestion.
  • This instrument cannot digest samples containing the following: explosives, propellants, pyrophoric chemicals, hypergolic mixtures (nitric acid and phenol, triethylamine, or acetone, etc.), animal fats, aviation fuels, acetylides, glycols, perchlorates, ethers, lacquers, alkanes, ketones and alcohols.

 

 

 

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Site manager: Donna Jacob

Otte phone: 701-231-8708,
Jacob phone:
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Last Updated: Thursday, May 23, 2013 6:04:42 PM