Quantification of Total and Soluble Inorganic Phosphate

Abstract

A simple, rapid, and sensitive colorimetric microassay for inorganic phosphate (Pi) relies upon the absorption at 660 nm of a molybdenum blue complex that forms upon reduction of an ammonium molybdate-Pi complex in acid. The method for determination of total Pi uses plant tissues that have been ashed at 500 °C, whereas quantification of soluble Pi is performed with tissues extracted under mild acid conditions (which preserves acid-labile phosphate ester bonds).