An inversion algorithm based on a forward optical model based on a radiative transfer equation is developed in terms of IOPs with explicit inclusion of the volume scattering function (VSF). Key results from the analysis are: 1) the inversion retrievals perform to comparable levels as the operational configuration of the NASA's Generalized Inherent Optical Property (GIOP) framework; 2) closure error between RT rrs and measured rrs have no significant effect on predicting the accuracy of the derived IOPs; and 3) $\tilde {b}_{bp}$ is important to ZTT, but not explicitly included in other types of comparable semi-analytic algorithms.