Cosima Stubenrauch, Judith Schlarmann and Reinhard Strey

Phys. Chem. Chem. Phys., 2002, 4, 4504 (DOI: 10.1039/b205728j). Amendment published 25th April 2003

In a recent paper we reported a surface tension isotherm for aqueous solutions of the nonionic sugar surfactant n-dodecyl--D-maltoside (-C₁₂G₂).¹ Unfortunately, we have made a (small, but significant) mistake in calculating the concentrations. Instead of a molecular weight of M = 510.62 g mol^–1 for -C₁₂G₂, inadvertently the molecular weight of the corresponding glucoside, namely n-dodecyl--D-glucoside (-C₁₂G₁), has been used in ref. 1. As M(-C₁₂G₁) = 348.48 g mol^–1 = 0.683 M(-C₁₂G₂) the concentrations c given in ref. 1 have to be multiplied by a factor of 0.683. In Fig. 1 presented here the (c)-data, as originally published,¹ are given as full circles. Multiplying the concentrations by 0.683 leads, due to the logarithmic scale, to a parallel shift towards lower concentrations at the same respective surface tensions (hollow circles). In order to be on the safe side we repeated the measurement of the whole surface tension isotherm once more. The new experimental results (full triangles) and the previous, now correctly plotted results of ref. 1 confirm each other within the experimental error. The slightly lower value of at concentrations above the c.m.c. is probably due to the use of a different batch of surfactant. However, the critical micelle concentration c_c.m.c. is not influenced demonstrating the reliability and accuracy of surface tension measurement in this concentration and surface tension range.

	Fig. 1 Surface tension as a function of the surfactant concentration c for aqueous solutions of n-dodecyl--D-maltoside (-C12G2) as published in ref. 1 (full circles), recalculated according to c = 0.683 cpublished in ref. 1 (hollow circles), and remeasured (full triangles). Accordingly the absolute error is about a symbol width. The lines represent fits of the Langmuir–Szyskowski isotherm (eqn. (1)).

As can be seen in Fig. 1, the new curve is in accordance with the recalculated one. On the basis of these two (c)-curves we determine the c.m.c. to be c_c.m.c. = (0.16 ± 0.01) mM instead of the erroneous (0.22 ± 0.02) mM in ref. 1. The full lines in Fig. 1 are a description of the surface tension by a Langmuir–Szyskowski isotherm.

(1)

As can be seen from the functional form of eqn. (1), only the parameter a extracted from the Langmuir–Szyskowski fit is directly affected by our mistake. The concentration a denotes the point at which 50% of , the maximum surface concentration, has been reached (see Table 1).

Table 1 Critical micelle concentration cc.m.c., maximum surface concentration ¥, and concentration a at which 50% of ¥ has been reached; these parameters were used for calculating the full lines in Fig. 1
Surface tension isotherm	cc.m.c. / mM	a / 10–6 mol l–1	¥/ 10–6 mol m–2
Ref. 1	0.22	8.19	4.68
Ref. 1, corrected	0.15	6.09	4.82
New measurement	0.17	4.59	4.45

While we are sorry for the mistake, it is important to underline that the effect of our mistake is limited to the surface tension isotherm and the parameter a extracted from the (c)-curve. Although all the concentrations given in ref. 1 have to be multiplied by 0.683, the shift towards slightly lower concentrations influences neither the theoretical analysis of the main experimental result of ref. 1, the disjoining pressure (h)-curves, nor the overall discussion of both the (c)-curve and the (h)-curves.

1. C. Stubenrauch, J. Schlarmann and R. Strey, Phys. Chem. Chem. Phys., 2002, 4, 4504.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

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