Table 1.

Proton exchange rates and association constants (K_A) for formation of the major lactate•EuDO3A species at four pH values at 298K.

pH	kex (s−1)47ppm[a] lactate•EuDO3A	KA (M−1)[b]	kex (s−1)[d] lactate
5	3610±360	95±4	N/A[c]
6	2469±250	45±3	336±33
7	2179±220	42±4	131±13
8	4082±400	151±8	790±79

^[a]Determined using the Omega method by varying B₁ from 2.35~23.5 μT and a pre-saturation time of 10 s.

^[b]Determined by fitting CEST titrations collected using a B₁ of 23.5 μT and a pre-saturation time of 10 s.

^[c]Fast proton at pH 5 precluded this measurement.

^[d]Determined using the Omega method and three saturation powers (0.67 μT, 1.01 μT and 1.35 μT) and a 10s pre-saturation period. Lactate was dissolved in D₂O/H₂O (1:1).