C18 HPLC Column, 250 x 4.6mm, 5μm — Sales and Instrument Support

General-purpose reversed-phase C18 column, 250 mm long x 4.6 mm internal diameter, packed with 5 µm porous silica particles carrying a bonded octadecylsilane (C18) phase. This is the USP L1 packing that the majority of routine pharmacopoeial and QC methods are written against.

At 4.6 mm bore the usual working flow rate is around 1.0 to 1.5 mL/min. A column of this size holds roughly 2.5 to 3 mL of mobile phase, so the ten column volumes normally used for equilibration are about 25 to 30 mL - worth knowing when a gradient method looks irreproducible at the start of a sequence.

Working limits and column life

• Standard bonded silica is used between about pH 2 and pH 8; outside that range the silica dissolves or the bonded phase is stripped, and the damage is permanent.
• A guard column of the same chemistry is the cheapest way to extend life on dirty matrices.
• Always flush buffer out with water before switching to organic, or the salt precipitates on the frit.
• Rising back pressure with peak splitting usually means a blocked inlet frit or a collapsed bed, not a worn phase.

Selectivity differs between manufacturers even at the same particle size and length, so a validated method should be re-verified when the column brand changes.