Table 3. Optimization of Neutralization Conditions to Prepare HP H¹³CO₃^– Formula in D₂O.

trial no.	neut. med.	molar ratio of Tris/GLC	time after dissolution (s)	T1 at 1.4 T (s)	%Pol of the first spectrum	pH*38
8	DCl (1 M)		62		<1.0	8.54
9	Citric acid (5 M)		67	63.8	16.4	7.39
10	Tris·HCl (1.0 M)/DCl (1.0 M)	1.40	64	59.7	15.6	7.30
11	Tris(1.2 M)/DCl(2.0 M)	2.25	57		3.2	7.30
12	Tris(1.2 M)/DCl(1.5 M)	2.40	61	59.5	16.3	7.78
13 (n = 7)	Tris(1.5 M)/DCl(1.5 M)	3.00	51 ± 2	66 ± 8	44 ± 2	7.76 ± 0.05