The on-line cleanup step provides the benefits of efficient matrix elimination, time savings, and convenience. Application Brief 165:Determination of p-Toluenesulfonic Acid in Water-Insoluble Drugs shows that this approach—performed on an integrated IC system that includes sample preparation capability and uses an ion chromatography column designed for separation with sodium carbonate/sodium biocarbonate eluents—demonstrates good linearity with a method detection limit of 1 mg/L.

p-Toluenesulfonic acid—an aromatic organic acid—is widely used in the pharmaceutical industry as a counterion for basic drugs because of its strong acidic and hydrophilic properties. Therefore, for drug quality control and authenticity testing, it is important to determine the content of p-toluenesulfonic acid in drug substances and products. Using an on-line matrix-elimination step, this new method successfully removes off-line sample preparation for the determination of p-toluenesulfonic acid in water-insoluble drugs.