This project addresses the paucity of literature on trimetallic nitride fullerenes possessing carbon cages larger than C₈₀. Herein, we present our chemical isolation of Gd₃N@C₈₈, which was selected based on the (1) few reports describing its fundamental chemistry and (2) curiosity of its candidacy as an effective MRI contrast agent. To date, MRI contrast agent development for metallic nitride fullerenes has focused on the more ubiquitous and smaller-cage Gd₃N@C₈₀ species. Excitement for Gd₃N@C₈₈ is predicated, in part, on the projected increased reactivity of its C₈₈ cage. The higher reactivity could, in principle, allow more attached hydrophilic groups, which in turn would translate into better water-solubility and improved clearance from the body in biological systems. Prior to any application, though, the fundamental science must first be performed. We demonstrate that the unique chemical reactivity of Gd₃N@C₈₈ can be strategically manipulated into a separation strategy for its isolation from complex extract mixtures containing more than 50 different species of fullerene and metallofullerene contaminant species. We describe the use of amino alcohols and Lewis acids to obtain highly enriched samples of greater than 90% purity. For subsequent studies (e.g., medical) demanding a higher purity (>99%), the appropriate HPLC parameters and fraction collection are also discussed.