Boron is extracted from 5.0 g of soil using 20 ml of hot CaCl2. CaCl2 is used because the Ca will flocculate the fine particles and the extract will filter easily and be clear, which is necessary for ICP-OES analysis. One standard is extracted for every fifteen unknown samples, with a minimum of one standard used. This extraction procedure takes approximately one hour to complete. 


Boron in soil is extracted using hot water. The extract can be analyzed using ICP-OES.


  • Balance
  • Falcon Tubes
  • Glass stir rods
  • Hot plate
  • Large glass beaker
  • Whatman #1 filter paper
  • Glass or plastic funnel
  • ICP sample vials
  • ICP sample vial holder


0.01M CaCl2


  1. Weigh 5.0 g of dry soil into a clean, dry, labeled Falcon tube.
  2. Measure 20 ml of 0.01M CaCl2 into each Falcon tube.
  3. Stir with a glass stir rod; leave the rod in the tube.
  4. Place each Falcon tube in the large glass beaker (or multiple small glass beakers).
  5. Add water to the large glass beaker up to the level of the water in the Falcon tubes.
  6. Place the large beaker on the hot plate.
  7. If the bottom of the beaker is very smooth, add a pinch of soil to the large beaker to provide a places for bubbles to form.
  8. Turn on the hot plate to high.
  9. Once the water is almost boiling (95°C), turn the heat down slightly.
  10. Keep the soil around 95C for a half hour, stirring occasionally.
  11. Place the labelled ICP sample vials in the sample holder and insert a funnel into each.
  12. Fold a Whatman filter paper and place in each funnel.
  13. Pour the supernatant into each funnel and wait for the liquid to filter through.
  14. Analyze the filtrate using ICP-OES as soon as possible.