Mortazavi Nik, Vahid, Konoz, Elaheh, Feizbakhsh, Alireza, Mehrdad  Sharif, Amir Abdullah. Development of a Pre-concentration Method for Nickel in Chocolate Samples using Magnetic Dispersive Solid- phase Extraction Followed by Flame Atomic Absorption Spectrometry. Journal of Applied Chemical Research. 2021;15(3):58-75. doi: