Interestingly, the agreement between the measured and nominal concentrations was better for C18-BAC than C16-BAC. Moreover, the chemical loss of C18-BAC was not particularly high at low concentrations, in contrast to C12-16-BACs. We speculate that C18-BAC was not completely dissolved into its free form and that colloidal association might have occurred with C18-BAC in water in the presence of methanol (0.01% v/v). Thus, the measured Cw may include a fraction of C18-BAC that was not available for sorption. Note however that the critical micelle concentration (CMC) of C18-BAC in deionized distilled