Determination of Phosphorus in Fruits and Fruit Products by a Spectrophotometry Molybdovanadate Method and by the Official Gravimetric Quinoline Molybdate Fertilizer Method

Abstract

Abstract A newly developed spectrophotometric molybdovanadate method and the official gravimetric quinoline molybdate fertilizer method, 2.025(b), slightly modified, were used to determine phosphorus in fruits and fruit products. In the former method, the use of hazardous perchloric acid is avoided by dry-ashing the sample as in method 20.017 and by using nitric acid rather than perchloric acid in the molybdovanadate reagent. In the quinoline molybdate method, the sample is dry-ashed in the same way. In both proposed methods, the official ash solution is used for the phosphorus determination as in the official volumetric method, 20.031–20.032. Ash weight can be obtained before preparing this solution; in the official colorimetric method, however, a second aliquot must be dry-ashed for the ash weight. The two proposed methods gave results in good agreement with those obtained by the official volumetric method. These methods are simpler and faster than the two present official methods.