Halo columns: new generation technology for high speed liquid chromatography.

Fast speed and high sample loading and the pressing demands of industries and researchers are compelling scientists and manufacturers to explore the new horizons in column technology. Recently, superficially porous silica particle columns are manufactured with some salient features such as super fast speed, sharp peaks, good sample loading, and low backpressure. The commercially available columns are Halo (Advanced Material Technology, Wilmington, DE), Express (Supelco, Bellefonte, PA), and Proshell 120 (Agilent, Santa Clara, CA). Halo columns are of C(8), C(18), RP Amide, and HILIC types with 2.7 microm over all diameters, 0.5 microm porous thick layers containing 90 A as pore diameter, and 150 m(2)/g surface area. These columns have been used for fast separation of low molecular weight compounds with some exception for large molecules such as protein, peptides, and DNA. The present article describes the importance of these state-of-the-art superficially porous silica particles based columns with special emphasis on Halo columns. The different aspects of these columns such as structures, mechanism of separations, applications, and comparison, with conventional columns have been discussed.