Uncertainty‐Aware Determination of the Apparent Critical Micelle Concentration of Crude Egg Lecithin in Water at 25°C From Triplicate Surface‐Tension Data

ABSTRACT Crude egg lecithin is a compositionally heterogeneous phospholipid preparation often summarized by a single surface‐tension breakpoint. Here, triplicate surface‐tension measurements in water at 25°C were reanalyzed using four continuous segmented models and a smooth hyperbola on two concentration scales, giving six candidate models. The flat post‐breakpoint log 10 ‐concentration model received the greatest support (Akaike weight = 0.726) and yielded an apparent critical micelle concentration (CMC) of 0.669% (w/v) (fixed‐model bootstrap 95% CI, 0.590%–0.764%, conditional on within‐level resampling under the selected model). The flat linear‐concentration model retained non‐negligible support (weight = 0.263; ΔAICc = 2.03) and yielded 0.556% (w/v), demonstrating model‐form dependence. Akaike averaging across the four segmented candidates gave an apparent CMC of 0.639% (w/v) (model‐averaged SE = 0.057%, conditional on this candidate set) and an approximate sensitivity envelope of 0.53%–0.75% (w/v), not a confidence interval. A two‐line comparator gave 0.558% on the linear scale and 0.726% on the log scale. Surface tension and surface pressure at the primary breakpoint were 46.03 and 25.94 mN m −1 , respectively. Surface excess and minimum molecular area were window‐sensitive (4.43–5.06 μmol m −2 and 32.84–37.50 Å 2 ), with relative statistical uncertainties of approximately 20%–35%, comparable to or larger than the window‐to‐window variation. Descriptors requiring an assumed molecular weight, aggregation‐number data, conductivity data, or defined molecular geometry were withheld. The apparent CMC is therefore an operational, model‐dependent descriptor rather than a unique molecular constant.