Bacterial endotoxin, a major quality of parenteral pharmaceuticals, is negatively charged lipopolysaccharide (LPS). A depth filter chemically modified to carry positively charged functional groups is applied to remove endotoxin from aqueous solutions and buffers through charge interaction. The environmental conditions, such as pH and electrolytes, known to affect the efficiency of endotoxin removal by the filter were studied. The charge character of the solid filter was titrated potentiometrically. Other factors such as pyrogen concentration and flow rate were also studied. The effectiveness of depyrogenating the aqueous solution by endotoxin removal through charge interaction with the depth type filter cartridge is fully demonstrated. An optimized cartridge performance can be achieved by following the conditions illustrated in this report. A multi-cell cartridge capable of processing bulk volume of fluid at or over 5 GPM makes it an effective depyrogenating device for the pharmaceutical industry.