Use of heterogeneous biosensors in microfluidic channels for diagnostic and detection of diseases in early stages is a novel, relatively cheap and applicable solution for saving lives and health purposes. It has attracted great interest in experimental field and a lot of works are being done in order to reach better biosensors with reliable results and fast detection. A comprehensive numerical model of Langmuir-Hinshelwood mechanism would help speeding up the process of design and analysis of biosensors. For this means we have developed a code in Fortran to simulate flow inside a microfluidic channel combined with Langmuir-Hinshelwood reactions on the surface of the biosensor. Control-volume based finite-element method (CVFEM) with high order discretisation has been used to solve full Navier-Stokes equations with chemical reactions on the biosensor. Results has been validated with existing experimental data from literature. The influence of target concentration as well as the inlet velocity (flow rate replica) on the biosensor saturation time, moreover, investigated in this study. The results show that as the inlet velocity and concentration increases the time that concentration on the surface of biosensor reaches its asymptotic value decreases, although increase in inlet velocity does not have any effect on dissociation stage of binding cycle.