Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been widely used for the analysis of pharmaceuticals in complex biological matrices due to its high sample throughput,selectivity and sensitivity.Commercially available sub-2 um particles have demonstrated the ability to maintain assay accuracy and robustness while reducing cycle times.However,as pressure increases with the inverse square of the decreasing particle size,the use of these small particles often requires specialized HPLC systems capable of withstanding backpressures of up to 15,000 psi.The recent commercialization of fused-core particle technology presents a new option for HPLC bioanalysis.With a 1.7 um solid silica inner core surrounded by a 0.5 um porous silica shell,the material has a shortened diffusion path which allows for rapid mass transfer and thus reduced axial dispersion and peak broadening.