New method of phosphorus determination with improved pretreatment of occluded iron phosphate fraction in soils

Abstract

In the sequential fractionation of phosphorus (P), a modified approach in the oxidation process of the occluded fraction of P (in iron oxides in soils) using redox titration in nitric acid (HNO₃) medium is presented. Also a new spectrophotometric method to determine that P fraction as the phosphomolybdate complex using a mixture of isobutyl acetate and methyl isobutyl ketone to extract the formed complex into the organic phase. Radioactive tracer (³²P) and sequential extraction is used to state the yield of extraction of the phosphomolybdate complex. Accuracy, precision, detection limit, and the linearity of the present method are 1.04%, 0.0322 μg mL^‐1, 0.0038 ug mL^‐1, and 0–15 ug mL^‐1, respectively. The results correlate significantly with the results of the standard method of Petersen and Corey (1966), and the procedure saves time (50 min) and chemicals.