In conclusion, we have demonstrated that hyperpolarized [1- C]fumarate can be formed in hundreds of millimolar concentrations via PHIP, with typical 13 C polarization levels of 30-45%. We show that acid precipitation as a pure solid and subsequent redissolution as a salt is an effective method to purify the hyperpolarized [1-13 C]fumarate from toxic contaminants in the chemical reaction solution, and that there is no measurable polarization loss caused by the precipitation and redissolution to within the measurement error. The method presented here is demonstrated on fumarate because it rapidly precipitates in acidic solution; we hope that exploiting the physicochemical properties of other molecules might allow for the purification of alternative hyperpolarized targets.