Curve‐fit Errors in Langmuir Adsorption Maxima

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Abstract
Although the Langmuir equation does not always adequately estimate “adsorption” maxima, it remains useful for empirical description of data. The test of data fit to the equation has usually been by linearity of the “Langmuir plot,” viz. concentration/adsorption plotted as a function of concentration. This test, however, is inadequate because the plotting of concentration against itself reduces data variability and always provides a statistically significant correlation coefficient. A better test of fit is to ascertain whether the adsorption isotherm has the shape of the equation model. When isotherms do not have the correct shape and only low concentration data is used, the equation can provide estimates of the adsorption maximum that are in error by 50% or more.