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SOP: Estimation of Organic Matter in Water

GIFSQ — Global Institute for Food Safety & Quality

Principle

After the estimation of total solids, the residue is ignited and the loss in weight is recorded as organic matter. The loss may also include (i) loss of residual water of hydration, (ii) evolution of CO₂ from carbonates, (iii) oxygen from nitrates, and/or (iv) volatilization of ammonium salts, so this is not a very reliable method for determining the amount of organic matter.

Procedure

Carry out the determination of total solids

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Ignite the dried residue

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Record the loss in weight as organic matter

Note: a more precise method is to estimate the ammonia given off by the organic matter when the water is distilled with a strongly alkaline solution of potassium permanganate, and to determine the oxygen absorbed from an acid solution of the permanganate. The albuminoid nitrogen method based on this principle is given as a separate SOP.