Unprocessed samples originating from grains usually contain ~ 97% of the total phosphorus content as phytic acid and therefore can be accurately measured using Phytic Acid (Total Phosphorus) Assay Kit .
When analysing more pure forms of phytic acid (inositol hexakisphosphate) (e.g. Sigma product P8810) the Phytic Acid Assay Kit (K-PHYT) is very accurate and is able to generate results within ~ 2% of the value stated for the product after taking into account the purity and moisture content of the dry sample.