A summary and critique of the various spectrophotometric methods used to quantify C-phycocyanin concentration

Abstract A wide range of research has been conducted on various applications and purification methods of C-phycocyanin (C-PC). In the published literature, there has not been consistency in the methods used to determine the concentration of C-PC within solution. This is an important characteristic to accurately determine the efficiency of a C-PC purification process and the quality of a final C-PC product. This brief report aims to critically evaluate the equations used to calculate C-PC concentration from spectrophotometric readings published in literature by discussing the logic behind the different coefficients and wavelengths used as well as by comparing the concentrations obtained for a Spirulina derived C-PC sample using the various equations. Some of the equations investigated, predominantly those which only differed slightly in the measured wavelengths, generated similar concentration results. However, these were based on work initially done on a specific cyanobacterium, Fremyella diplosiphon (Bennett and Bogorad 1973). Equations generated using other cyanobacteria extracts or even species of macroalgae generated markedly different C-PC concentrations. When these equations have been used in literature, there is often no distinction made as to whether the algal species being investigated is the same as the one used to develop the equation originally. The goal of this investigation was therefore to highlight this issue so that a more consistent and microalgal-species-appropriate approach can be used in the future for quantifying C-PC concentration in solution.