Preparation of triple acid extract

TRIPLE ACID EXTRACT

Aim:

         To prepare triple acid extract of plant material for nutrient analysis

Principle:

         The organic constituents of the plant are hydrolyzed and converted into soluble inorganic constituents by the action of tri acid mixture. By mixing concentrated nitric, sulphuric and perchloric acids in 9:2:1 ratio, triple acid mixture is prepared.

The triple acid extract of plant material is prepared for the estimation of total P, K, Ca and Mg.

Reagents required

Triple acid mixture containing 9:2: 1 ratio of concentrated nitric, sulphuric and perchloric acids.

Procedure

ü  Weight about 1 g of the given plant sample into a 100 ml conical flask.

ü  Add 15 ml of the triple acid mixture and cover the mouth of the flask and keep it over over a sand bath

ü  Continue heating until the contents is reduced to about 2-3 ml of colourless clear solution.

ü  If white residue is not obtained, the residue should be treated again with 2 ml of the tri acid mixture and the heating be continued till the contents is reduced to about 2-3 ml. Thereafter, the beaker be removed from the sand bath.

ü   Allow the beaker to cool.

ü  Add 5 ml of distilled water into the beaker containing digested residue.

ü  Heat the contents gently until white fumes appear.

ü   Remove the beaker and let it cool. Then, add 10 ml of distilled water and heat the contents to dissolve the residue.

ü  Take a 100 ml clean volumetric flask fitted with a funnel lined with Whatman No. 42 paper.

ü  Transfer the contents of the beaker into the funnel using a glass rod collecting the filtrate in the volumetric flask.

ü   Rinse the beaker with about 15 ml portions of glass distilled water and transfer each rinsing into the funnel in order to transfer the digested residue quantitatively.

ü  Collect the filtrate from each washing into the same volumetric flask.

ü  Then wash the residue on filter paper with small portions of distilled water and collect the washing until the volume of filtrate reaches 100 ml mark. Stopper the flask, label it and use it for further analysis of P, K, Ca and Mg concentrations.