Revision of the calibration experiment in asymmetrical flow field-flow fractionation

Abstract

Asymmetrical flow field-flow fractionation is a versatile chromatographic fractionation method. In combination with at least one detection technique it is used for size-based separation of colloids, biomolecules and polymers. Although often used as pure separation method, a well-elaborated theory is available that allows precise quantification of the translational diffusion coefficient D. Still, current literature suggests different ways to transform this theory into applicable experimental procedures and no “gold standard” for correct data processing exists. While some sources report a direct way to extract diffusion information from the fractogram, others suggest the necessity of an external calibration measurement to obtain the channel width w. In this work, we compare the different approaches and calibration algorithms based on original and literature data using our own open-source AF4 evaluation software. Based on the results, we conclude that available AF4 setups do not fulfill the requirements for absolute measurements of D. We show that the best way to conduct is to consider the area of the channel and D of the calibrant while neglecting the small peak which occurs in the void peak region.