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.