Determination of trimetaphosphate added to soils

Abstract

Unlike other inorganic phosphates, trimetaphosphate (TMP) is not adsorbed by soils. Trimetaphosphate in soils is hydrolyzed chemically and biochemically to triphosphate, which in turn is hydrolyzed further to pyrophosphate and orthophosphate. Studies on hydrolysis of TMP added to soils are desired, but no method is available for determination of this phosphate when present in mixtures containing other phosphates. Therefore, a method was developed for determination of TMP in mixtures containing ortho‐, pyro‐, and triphosphate. It involves treatment of a soil sample with a buffered (0.1 M Tris, pH 8) solution, precipitation of the orthophosphate and linear polyphosphates by the addition of BaCl₂, and determination of the TMP remaining in the supernatant by a molybdenum blue method after acid hydrolysis at 80°C for 1 h. The method is simple and precise and allows quantitative determination of TMP added to soils.

Key words:

• Polyphosphates
• Colorimetric method
• Trimetaphosphatase

Notes

Journal Paper No. J‐11464 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, Iowa. Projects 2112 and 2431.

Graduate Research Assistant and Professor of Soil Chemistry.