Stopless flow injection in asymmetrical flow field-flow fractionation using a frit inlet.

Stopless flow operation of asymmetrical flow field-flow fractionation (FFF) has been achieved by introducing a hydrodynamic relaxation method using a frit inlet. By using frit inlet injection, a focusing process which has been an essential part of runs at the asymmetrical flow FFF system can be completely avoided. Band broadening of an initial sample zone during hydrodynamic relaxation is discussed with equations related to the ratio of two inlet flow rates. For the successful achievement of particle relaxation and separation, it is necessary to apply a small ratio of sample inlet to frit inlet flow rate. Experimental results are reported for the evaluation of the system efficiency at various levels of hydrodynamic relaxation and for both normal and steric/hyperlayer modes of FFF runs using latex standards. Most importantly, it is shown that a high resolution and a high-speed separation of submicrometer-sized latex mixtures can be accomplished in asymmetrical flow FFF without using the conventional focusing relaxation process.