Expanding the elution by characteristic point method to columns with a finite number of theoretical plates

• ECP method was expanded to columns with a small number of theoretical plates.
• Influence of axial dispersion and injection profile were determined by a tracer.
• Uncertainty analyses of the expanded ECP method was done.
• Expanded ECP method showed similar uncertainties like standard batch method.
• Material consumption could be reduced by nearly one order of magnitude.

The elution by characteristic point (ECP) method provides a rapid approach to determine whole isotherm data with small material usage. It is especially desired wherever the adsorbent or the adsorbate is expensive, toxic or only available in small amounts. However, the ECP method is limited to adsorbents that are well optimized for chromatographic use and therefore provide a high number of theoretical plates when packed into columns (2000 or more for Langmuir type isotherms are suggested). Here we present a novel approach that uses a new profile correction to apply the ECP method to poorly optimized adsorbents with less than 200 theoretical plates. Non-ideality effects are determined using a dead volume marker injection and the resulting marker profile is used to compensate the named effects considering their dependency from the actual concentration instead of assuming rectangular profiles. Experimental and literature data are used to compare the new ECP approach with batch method results.