Direct Introduction of Milk Sample in FIA System for Phosphorus Determination

Abstract

This work regards the determination of phosphorus in milk using a flow injection analysis (FIA)system. The determination is based on well known reaction between phosphate ions and an ammonium molybdate reagent, originating the ammonium phosphomolybdate complex, which is then reduced to form a blue compound of molybdenum that can be spectrophotometrically determined at 700 nm. Innovation of system is the on-line sample treatment, using nitric acid 5% (v/v) in flow causing the precipitation of proteins which were separated in a filter coupled to FIA. The method was compared with the well-established mineralization procedure, employing microwave assisted digestion procedure and the results were in agreement (paired t-test, p=0.05). The precision expressed as coefficient of variation for triplicate measurements was always lower than 10%. The limit of quantification was 0.572 mg L -1 .