There are two approaches that can be used for inhibition studies, incubation method and direct method (without incubation), and in this study the latter was employed. It was observed that when using the direct method, it is difficult to attain
the concentration that causes 50% inhibition (IC50); this worked reasonably well for Cd2þ (51.1%) with the value for IC50 calculated as 3.13 ppm but was not successful for Pb2þ and Cu2þ. Therefore, unlike Cd2þ, in order to attain the 50% inhibition (IC50 value) for Pb2þ and Cu2þ, either a higher concentration of the metal can be used or the incubation method can be employed.