For deuterium oxide solutions of various compounds including cyclic and acy
clic saccharides, oligoglycines, and sodium chloride., the proton chemical
shifts of these solutes and the tetramethylammonium ion (TMA), referred to
an external standard, change linearly with the molarity of solute. This slo
pe is almost independent of the kind of protons of solute and TMA and is pr
oportional to the product of the molar volume of the solute and the differe
nce in volume magnetic susceptibility between deuterium oxide and the solut
e. The equilibrium formation constant and structure of ion-pair of TMA and
the benzenesulfonate ion (BS) are evaluated from chemical shifts referred t
o an internal standard. At least some of the four methyl groups of TMA in t
he ion-pair complex are located above the benzene ring of BS. This structur
e indicates that TMA and BS form their ion pair by hydrophobic and electros
tatic attraction. These results serve not only for choosing appropriate int
ernal references and internal or external standard methods for chemical shi
ft measurements in aqueous solutions but also for correcting the chemical s
hift referred to the external standard.