“…The reviewed studies can be divided into three categories. Spectrophotometric methods by reducing cupric ions [ 4 , 26 ], titration with 2,6-dichlorophenolindophenol (Titration) [ 18 , 24 , 36 , 40 , 43 , 45 , 47 , 48 , 51 ], and chromatography such as High Performance Liquid Chromatography (HPLC) [ 25 , 29 , 30 , 31 , 32 , 33 , 35 , 38 , 39 , 41 , 42 , 44 , 46 , 49 , 50 , 52 , 53 ]. Five papers did not mention the analytical method used [ 27 , 28 , 34 , 37 , 54 ].…”