K-INOSL measures free myo-Inositol and will not measure any that is bound.
To free this myo-Inositol for measurement we would suggest following the total phosphorous instructions in step B (ENZYMATIC DEPHOSPHORYLATION REACTION) page 7 of the K-PHYT booklet (linked below).
Following the centrifugation step, you can use the supernatant in K-INOSL to measure then amount of myo-inositol present.
You may need to adjust the amount of sample used during step B of K-PHYT to ensure your sample is within the measurable range of K-INOSL. This can be done by decreasing the volume of distilled water by the amount of sample added.
Please note there will be interference from glucose too as this reacts more slowly. For this reason we do not measure phytic acid via myo-inositol, if you wish to measure phytic acid I would recommend K-PHYT (Linked below).