Figure 4: Graphical representation of potentiometric curve for content of free amino group. and represent the volume of 0.1 M NaOH needed to neutralize excess of free HCl and carboxyl group of OCM-CS. is the volume of 0.1 M NaOH required to neutralize the carboxyl group and HCl associated with NH2 functional group of OCM-CS. Abbreviations: ΔpH, change in pH.