Fused-core particles: a practical alternative to sub-2 micron particles.

The benefits of sub-2 micron particle size columns have been widely researched and published. The use of these columns on ultrahigh-pressure liquid chromatography (UHPLC) instrumentation may lead to increased efficiencies and higher throughput. However, these instruments may not be readily available to the pharmaceutical chemist. Within the past year, a practical alternative has been introduced which offers increased efficiencies, but at conventional HPLC pressure limitations. These particles are called fused-core particles and are comprised of a 1.7-micron solid core encompassed by a 0.5-micron porous silica layer (dp = 2.7 micron). The goal for this research was to test these columns for efficiency and robustness utilizing a mixture of Torcetrapib and its relative impurities. Our results indicate that excellent theoretical plates (approximately 14000) were achievable for run times less than 5 min. Compared to the Waters Acquity particles, the fused-core particles achieved approximately 80% of the efficiency but with half the observed backpressure. Our robustness results concluded that these separations were reproducible for at least 500 injections while the % RSD for retention time, theoretical plates, peak asymmetry, and resolution was found to be less than 1%.