A Brief Introduction Of Filter Paper
Filter paper, made of cotton fiber is a filter tool commonly found in chemical laboratories to separate liquid and solid.
Paper chromatography is inert support for filter paper. The filter paper fiber has a strong affinity with water and can absorb about 22% of water, and 6~7% of the water is combined with the hydroxyl group of cellulose in the form of the hydrogen bond, which is difficult to remove under normal conditions. While the affinity of the filter paper fiber to the organic solvent is very weak, so the general paper chromatography actually takes the combined water of the filter paper fiber as the stationary phase, with the organic solvent as the mobile phase.
When it passes the sample through the paper, the solute at the sample point is continuously distributed between the water and the organic phase. A part of the sample moves with the mobile phase, enters the solute-free region, and is redistributed at this time, and a part of the solute enters the stationary phase(aqueous phase) from the mobile phase. As the mobile phase moves, the various parts are continuously distributed according to their respective partition coefficients and moved along the mobile phase, thereby separating and purifying the material.
In general, the filter paper is divided into qualitative and quantitative. In analytical chemistry applications, the residue collected on the filter paper after separation of the inorganic compound by filtration can be used to calculate the rate of wastage during the experiment.
Qualitative filter paper is filtered to produce more cotton fibers, making it only suitable for qualitative analysis; Quantitative filter paper, especially the ashless filter paper, is more effectively resistant to chemical reactions after special treatment procedures with fewer impurities, which can be used for quantitative analysis.
Besides the filter paper for general laboratory applications, there are many filter paper applications in daily life and engineering. For example, the coffee filter paper provides high softness and high wet strength. Others use air filter paper for testing suspended particles in the air, and fiber filter paper for various industrial applications.
The technical indicators of the filter paper can be mainly divided into two aspects–filter characteristics and physical characteristics. Filtration characteristics include air permeability, air resistance, maximum pore size, and average pore size. Physical properties include basis weight, thickness, stiffness, corrugation depth, burst strength, resin content, and the like.