0.500 g of dried and ground plant material are heated at 600°C in a muffle furnac. All organic material incinerates, leaving the inorganic components. 5 ml of 20% HCl are added to dissolve the ash then diluted with 5 ml DI water, and this solution is analyzed using ICP-OES. Check samples are included every fifteen samples, with a minimum of one. Beginning the procedure (weighing the samples and recording their locations) takes approximately three minutes per sample. Samples are left in the furnace overnight.

Principle

Plant material is heated to a point where the organic components incinerate, leaving the inorganic components.

Equipment

  • High-form silica crucibles
  • Metal crucible holder
  • Muffle furnace
  • Metal spatula
  • Weighing paper
  • Balance

Reagents

  • HCl
  • DI water

Procedure

  1. Weigh 0.500 g of the dried plant material into the high form silica crucibles, noting the location of each sample, because chemical markings will come off during the procedure
  2. Include a check sample every 15 samples
  3. Place entire tube rack into the right side oven
  4. Close oven doors by pulling down the large lever on the left of the oven
  5. Flip on the power switch on the wall above the oven
  6. Rotate the small knob on the timer until it clicks and you hear a thump from the control box (under the furnace).
  7. Leave in the furnace overnight.

In the morning

  1. Turn off the power switch.
  2. Open up the oven halfway – the bottom door should open, but the top will stay closed.
  3. After an hour or so, open up the top door.
  4. Allow the oven to cool for another hour or so before removing the samples.
  5. The tube rack will still be very hot, so remove it with care and place on a non-combustible and non-melting surface.
  6. Once all of the tubes have cooled, add 5 ml of 20% HCl and let sit for 30 minutes.
  7. Add 5 ml of DI water and swirl to fully combine.
  8. Allow to settle for one hour.
  9. Decant the supernatant into labelled ICP tubes and analyze using ICP-OES.