Quantification of Total Phosphorus Content in Plant Material Using Microwave Digestion and Segmented Flow Analysis

This protocol aims to quantify the total phosphorus (P) concentration in leaf material through acid digestion and segmented flow analysis. This method has been tested on plant species including Australian Eucalyptus and other native understory species but could be applicable to foliar leaf material in general with minor modifications. Phosphorus content is often measured using a Kjeldahl digestion, which can be time consuming; we present this microwave digestion method using nitric acid and hydrogen peroxide as an alternative to reduce sample digestion times. This method is limited by the number of positions available in the microwave digestion rotor. Phases of analysis include: (1) acid digestion using microwave digestor (3 hours); (2) preparation of reagents (2 hours); and, (3) analysis for total P on the flow analyser using antimony-phospho-molybdate complexation reaction (30 minutes plus 90 seconds per sample).