Wet Ash Method for Ca, Mg and K Using Nitric Acid and 30% Hydrogen Peroxide.

 

1. Weigh +/- 200mg dried (60C) and ground (20 or 40 mesh) plant tissue into a digestion tube (20x150mm test tube - lignin tubes). Note: for K, use only 100mg of the NIST apple standard due to it's high K value.
   
2. Add 4ml of concentrated nitric acid (HNO3). Let it stand overnight.
   
3. Place tubes in the dry-block and heat at 120C for one hour. Remove and allow to cool.
   
4. Add 3ml 30% hydrogen peroxide (H2O2) and place tubes back in the dry-block. Repeat the additions of 30% hydrogen peroxide until the digest is colorless.
   
5. Remove from dry-block and allow to cool.
   
6. Pour each tube into a 50ml volumetric flask, rinsing the tube with DI water. Bring to volume with DI water and mix thoroughly.
   
7. For analysis on the ICP in EM-1, the solution needs to be filtered to at least 0.45µm..

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Reference;

Plant Analysis Handbook; Jones, Wolf and Mills 1991
Micro-Macro Publishing, Athens Georgia ISBN 1-878148-001
In Falcon Library at QK 865,J66

Laboratory Guide for Conducting Soil Tests and Plant Analysis
J. Benton Jones, Jr., CRC Press 2001 ISBN 0-8493-0206-4

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