Signal enhancement or polarization level alone does not indicate the total signal intensity available from the hyperpolarized species, which for many applications is a crucial parameter. We define as the key figure of merit molar polarization, which we take as the product of the carbon-13 polarization times the concentration of [1- C]fumarate molecules. For in vitro or in vivo studies using hyperpolarized biomolecules, important criteria for the solutions prior to injection/perfusion are 25 : (1) the concentration of the hyperpolarized species; (2) the polarization level (usually >10% is desirable); (3) purity from toxic contaminants, and; (4) the biocompatibility of the solution, i.e. being at physiological pH, temperature, and osmolarity. In this paper we will address these points in the context of our work forming fumarate via PHIP.