Mechanistic Origins of Pressure Reduction, Apparent Efficiency Gain, and Enhanced Detector Response in Radial Flow Stream Splitting Chromatography.

Radial flow stream (RFS) splitting has been reported to reduce operating pressure and apparent theoretical plate height (increasing column efficiency) while increasing detector response relative to conventional high-performance liquid chromatography column operation. However, the mechanisms responsible for these effects have remained unclear. Here, pressure measurements, computational fluid dynamics, and reduced-order outlet models were used to examine how radial outlet partitioning in the new end fitting alters column behavior. Most of the measured pressure reduction arose from post-column effects, although a smaller in-column contribution remained. Simulations showed that the radial outlet disrupted the conventional outlet-flow funnel and preferentially captured wall-adjacent flow. When the outlet models were applied to a published model of radial column heterogeneity, apparent column plate height decreased by approximately 19% and peak height increased by approximately 18%, consistent with typical experimental results. Experimental sensitivity improvements also persisted under detector conditions that were independent of flow rate. These results indicate that the reported benefits under RFS splitting mode arise from a combination of post-column pressure effects and selective sampling of the radial solute distribution.