Qualitative and quantitative filter papers for the clarification and purification of samples for analysis. Available in a range of sizes, counts, grades, and formats such as circles and sheets, they are often made from cellulose or nylon.

Filter papers are familiar laboratory consumables often used with a conical funnel or similar device to filter and retain solids, particulates, and other materials from aqueous solutions, suspensions, solvents, and other liquids. Filter papers may be manufactured from natural cellulose, nylon, or glass or quartz fibers. They are typically available as pre-cut circles of various diameters, which may be folded into pleats, quadrants, or pyramids. Some filter papers are also sold as sheets or rolls that can be cut to size as needed.

Filter papers may be categorized as qualitative or quantitative. Qualitative filter papers are used for general purpose filtration applications where subsequent analysis is not critical. Quantitative filter papers (ashless papers) are intended for more exacting analytical work and may be weighed or otherwise processed after use. They are made from low-linting fibers that are typically acid-hardened during their manufacture to provide high wet strength and chemical resistance, and are pre-rinsed with demineralized water for extra purity.

Most filter papers are also graded numerically according to pore size, which in turn infers other parameters such as flow rate, retention, thickness, weight, and burst strength, that constrain and prescribe their application.

What is Filter Paper Used for?
• General applications: research laboratories, clinics, and educational settings
• Analytical applications: precipitant and particulate removal prior to further analysis or assay
• Industrial applications: foods and beverages, cosmetics, and gravimetric analysis of cements, clays, and iron and steel products
• Environmental applications: water, soil, or atmospheric sample analysis