Determination of human cardiac intracellular pH using 31P-MRS is challenging as the resonance frequency of Pi is concealed by a close resonating 2,3-DPG signal originating from blood. Common short TR and low-flip angle scan used for cardiac 31P-MRS increase the effective SNR/time, but can additionally suppress the Pi signal intensity. We have investigated the feasibility of detecting cardiac Pi and calculating intracellular pH of human heart using long TR 3D-CSI examination with adiabatic excitation at 7T. Comparison to short TR acquisition was performed using interleaved TR measurements. We report robust and repeatable detection of Pi signal in 100% of subjects.