TABLE 3.

Cation transport numbers in water and in the skin during transdermal iontophoresis

			Water			Skin
Cation	Atomic weight	Ionic radius* (Å)	Hydrodynamic radius† (Å)	Mobility* (10−4 cm2·s−1·V−1)	‡	t°i, SC+ ± SD (Expt. S.C+)	t°i, M1 ± SD (Expt. M.1)
Li+	6	0.060	1.73	4.01	0.33	0.54 ± 0.06§(a)	0.13 ± 0.01§(b,c)
Na+	23	0.095	1.67	5.19	0.39	0.59 ± 0.06¶	0.18 ± 0.01§(b)
	18	0.133	1.14	7.60	0.49	0.77 ± 0.19§¶(a)	0.22 ± 0.02§(b)
K+	39	0.143	1.14	7.62	0.49	0.70 ± 0.15	0.22 ± 0.01§(c)

Values were deduced from the results of single-carrier and quaternary combination donor formulations.

^*Ionic radius and mobility data were taken from Atkins (32).

^†Hydrodynamic radius calculated from ionic mobility (32).

^‡The transport numbers in water were taken from Falk (31).

^§(a,b,c)Values significantly different (one-way ANOVA, Tukey test, p < 0.01).

^¶Values significantly different (one-way ANOVA, Tukey test, p < 0.05).