By Anonymous on Friday, October 29, 1999 - 11:27 am:
I'm working on a science project on paper chromatography, need general and specific info. Please help.
By Bruce Freeman on Friday, October 29, 1999 - 12:24 pm:
General information: When the bottom edge of a piece of paper is placed in a solvent, the solvent will travel up the paper. If a sample (like ink) is placed as a small (<5 mm) spot or narrow line above the level of the solvent (so it's not just washed away) the moving solvent will carry the sample components up the paper. How fast the components move depends upon the relative affinity of each component to the solvent and to the paper. When the solvent "front" gets near the top edge of the paper, the paper is removed from the solvent and allowed to dry.
There are a tremendous variety of solvents available for use pure or as mixtures. You can often succeed with the simplest solvents, and it is not always necessary to have extremely pure solvents.
There are a number of important details. The paper and solvent must be in a closed chamber so the air surrounding the paper is saturated with solvent. (Since most solvents are flammable, there is an element of danger in this.) The paper must not touch the solvent container, but must be suspended free from the walls. You must mark the starting point of the samples and the final position of the solvent "front" for later measurements.
This sort of information should be available in any text dealing with the basics of paper chromatography (or the related technique, "thin-layer chromatography").
More specific than that I can't get without knowing what you plan to do.
By the way, Material Safety Data Sheets are available over the Internet. Get copies of any for any chemicals you use, and read them. Pay particular attention to flammability and toxicity.
By Anonymous on Sunday, October 31, 1999 - 04:16 am:
Anyone know what selective absoprtion and color bands are? What do they have to do with paper chromatography?