Use of Relative Molar Sensitivity as a Specific Value for Evaluating Heptaoxyethylene Dodecyl Ether Concentrations in Methanol Solution

Relative molar sensitivity ( RMS ) determined using quantitative 1 H NMR and HPLC with a refractive index (RI) detector was applied as a specific value for quantifying the levels of heptaoxyethylene dodecyl ether (HOEDE), a typical non-ionic surfactant, in methanol solutions. RMS was robust against changes of the analytical conditions ( i.e. , RI cell temperature, acetonitrile content in the mobile phase, HPLC system). Furthermore, the obtained HOEDE concentrations using a previously evaluated RMS were comparable to those obtained using a reference method for over 1 year.