According to : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3429087/

For the solubility assay, the intestinal digests need to be centrifuged, to yield a supernatant and precipitate. The nutrients or compounds present in the supernatant represent the soluble components and measured by HPLC etc. Percent solubility is calculated as the amount of soluble compound relative to the total amount of compound in the test sample

* taking idea from: http://www.sciencedirect.com.ezproxy.lib.monash.edu.au/science/article/pii/S0963996906001530

Method:

Calculation

HPLC Area: 90.0 muA

Standard curve: Y= 300X

concentration: 90/300= 0.3ug/ml X (20 dilution) = 6ug/ml

6ugml X 80 ml (total volume gastric+intestine)= 480 ug/ml

Initial bioactive compound 10mg ~ 10000 ug

Total bioaccesible content: (480/10000) X100 = 4.8%

= 4.8ug/100ug

So is my method and calculation correct?