In this work, the effect of proton-exchange rate on Jspectra is studied by varying pH of the solution while keeping the same concentration of urea (8 M). As shown in Fig. , due to the increased proton-exchange rate in urea solutions, amplitudes of high-frequency peaks (120-150 Hz) gradually decrease without considerable line broadening at both lower and higher pH values. It is clear that, when the proton-exchange rate is much higher than J -coupling interaction (k ex J NH ), 1 H nuclei is effectively decoupled from the rest of the spin system and the J NH -coupling does not contribute to the observed zerofield spectra. Therefore, high-frequency peaks vanish in the spectra of highly acidic (pH = 1.4) and highly basic (pH = 14) solutions, which is also confirmed with simulations of the urea spin system (Fig. , see also Methods). The disappearance of the high-frequency peaks in highly acidic/basic conditions also bears a resemblance to the results shown in a recent study on zero-field NMR of ammonium in highly acidic conditions . The authors of Ref. reported that an increase in the proton-exchange rates causes the zero-field NMR signals of ammonium to vanish. This is explained by the nature of the experiment: after prepolarization in a strong field, a sample spends a significant amount of time (1 s) in a low-field region (tens of µT) before the detection in zero-field. In our experiment, we are limited to a shuttling time (time between prepolarization and signal acquisition) of 1 s, as for the shorter transfer times vibration noise, stemming from a transport of the NMR tubes, disrupts the structure of the spectra. For such a delay, water protons depolarize despite a guiding field of 10 µT. In the case of faster proton exchange, unpolarized protons are more often involved in the exchange procedure. This affects the "memory" of nuclei spin orders, resulting in the deterioration of amplitudes of peaks. To verify the influence of guiding field strength on the peak amplitude, the field was increased by an order of magnitude, which, due to the increased proton relaxation time T 1 , resulted in an up to ≈ 25% signal enhancement (Fig. ) . The increase of the signal amplitude in a higher guiding field is predicted to be universal for molecules under rapid chemical exchange and can be exploited in measuring zero-field spectra of such molecules. The boost in the signal stemming from a stronger "transfer" field may not only be beneficial for remote prepolarization experiments but also find use in ZULF hyperpolarization techniques relying on the chemical exchange , where a stronger magnetic field will slow down the relaxation of protons in solution and yield higher signal amplitudes in subsequent zero-field detection.