Theoretical and experimental investigation of the focusing position in asymmetrical flow field-flow fractionation (AF4)

Moreover, the effects of the sample-injection position, the spacer thickness, the membrane aging, and the nature of the injected sample on the focusing position were investigated: zfoc was not influenced by these parameters, proving the universal applicability of the equation given in this work for predicting the focusing position, when the assumption of constancy of the cross-flow velocity at the membrane, which underlies this equation, is fulfilled. Additionally, it is notable that this theoretical expression is suitable for different models of AF4 channel and not peculiar to specific suppliers.