I must sadly and repeatedly say that direct-utilization of photometer or fluorometer is not the quantitative method at all. The direct-utilization of photometer or fluorometer without purification is committing the crime against the Beer-Lambert's law.
Thus, we have recently demonstrated that HPLC-photometry gives three-fold higher values than direct-utilization of photometer (please see Fig. 10 of the file; JCB Fucoidan Transport).