Reverse phase (RP) HPLC columns are majorly advantageous in ensuring high precision data, they are widely available commercially and are easy to use and less time-consuming. Two main approaches one should consider before choosing a RP column are, firstly characterising physiochemical parameters of the packing material such as 1% carbon load, surface area, pore size, particle size and pH. These are some of the important parameters important to control the quality of the column. Second approach is based upon the chromatographic and statistical evaluation of the retention behaviour for a large number of compounds. Kromasil C18 columns are basically RP columns made up of silica-based monomeric type reversed-phase packing material.. L × I.D.: 150 mm × 4.6 mm. Particle size: 5 µm. Pore size: 100 Å. . . Sigma-Aldrich K08670356 Kromasil C18 HPLC Column, 5 µm Particle Size, 100 Å Pore Size, 4.6mm ID, 150mm Length. Country of Origin : Sweden. Part Number : 1199Z22EA. Pack of : 1.