Inorganic phosphate assay with malachite green: an improvement and evaluation.

An improvement over existing procedures for the determination of nanomole quantities of inorganic phosphate (Pi) is described. The protocol is simplified, and the effective concentration range of Pi in which the assay may be used is increased to 60 nmol/ml. Many of the substances commonly used in association with Pi assays (i.e. phosphohydrolase studies) are shown not to interfere with the measurement of Pi by this method. The effects of detergents and protein on the assay also were investigated, and methods for avoiding interferences by them are described.