Filter Paper
Filter papers are familiar consumables in the laboratory normally used with a conical funnel or similar device for the filtering and retention of solids, particulates and other contaminants from aqueous solutions, suspensions, solvents and other liquids. Filter papers are manufactured from natural cellulose linters or from glass or quartz fibres. They are available in various diameters as pre-cut plain circles, or as discs ready-folded into pleats, quadrants or pyramids for convenience and to maintain optimal, clog-free flow rates. Filter paper is also sold as sheets or rolls that can be cut to size as required.
Filter papers are described either as qualitative or quantitative. Qualitative filter papers are used for general purpose filtration applications where subsequent analytical outcomes are not critical.
Quantitative filter papers (ashless papers), are intended for more exacting analytical work. They are made from low-linting fibres that are typically acid-hardened during their manufacture to give high wet strength and chemical resistance, and are pre-rinsed with demineralised water for extra purity.
Most filter paper is also graded numerically according to pore size, which in turn infers other parameters such as flow rate, retention, thickness, weight, burst strength, and hence their nominal application.
What is filter paper used for?
- General applications in research laboratories, clinics and education
- In the analytical laboratory for removal of precipitants and particulates prior to further analysis or assay
- Industrial applications in foods, beverages, cosmetics and gravimetric analysis of cements, clays, iron and steel products
- Environmental analysis of water, soil or atmospheric samples