How Does the Filter Paper Achieve Liquid Separation and Purification?
In chemical laboratories, filter paper is essential. The common shape is a circle, which is mostly made of cotton fiber, using cotton pulp or refined sulfate wood pulp as raw material. After freely beating, the fiber is impregnated with hydrochloric acid for purification treatment, and it is made by the low-pressure press on a long wire paper machine.
Working process to achieve liquid separation and purification
The filter paper fiber and water have a strong affinity, which can absorb about 22% of the water, and 6~7% of the water is combined with the hydroxyl group of the cellulose in the form of hydrogen bonds, which is difficult to remove under normal conditions. The affinity of the filter paper fiber and the organic solvent is very weak, so the general paper chromatography actually uses the bound water of the filter paper fiber as the stationary phase and the organic solvent as the mobile phase.
The solute on the sample is continuously distributed between the water and the organic phase, as the mobile phase passes through the sample along with the paper. A part of the sample moves with the mobile phase and enters the solute-free zone.
At this time, it is redistributed. A part of the solute enters the stationary phase (aqueous phase) from the mobile phase. As the mobile phase continues to move, various parts are continuously distributed according to their respective partition coefficients, and move along the mobile phase, so that the material is separated and purified.
Filter paper classification- qualitative and quantitative
Filter paper is divided into qualitative and quantitative. For the qualitative filter paper, it contains more ash, which is used for general qualitative analysis and cannot be used for reiterating analysis. The quantitative filter paper is treated with hydrochloric acid and hydrofluoric acid, and distilled water, and the ash content is small.
It is suitable for precise quantitative analysis. In addition, there are chromatographic filter papers for chromatographic analysis. The selection of filter paper depends on the requirements of the analysis work for filtering sediment, the nature of the sediment, and the amount of sediment.
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