This document specifies the extraction and determination procedures for the phycobiliproteins C-phycocyanin (C-PC) and the complementary pigment allophycocyanin (APC) from dry samples of species belonging to the genus Arthrospira (Cyanobacteria, Cyanoprokaryota or blue-green algae)(nowadays referred to Limnospira, [1]), and commercially known as Spirulina. This document enables laboratories analysing Arthrospira samples to report accurate C-PC and APC concentrations and yields.