Sand-Starch mixtures as stationary phases: low-cost Columm Chromatography for dyes purification in Organic Chemistry class

Amongst the many contents to be discussed, the Introductory Organic Chemistry classes in Brazilian Universities also brings the purification methods in their curricular subjects to deal with. It is well established that chromatographic methods are the best choice for many organic chemists around the world1. Besides, it is very common to teach paper chromatography as the single example relatively to this technique, becoming the knowledge neither enough nor attractive to student. By one side, such fault is understood due to the expensive costs related to usual stationary phases (e.g. SiO2). Based on chomatography´s principle (chroma: color and graphy: written), an interesting experiment can be carried out with colored compounds which represents some important feature in social daily. Food dyes are good choices to be used since a lot of commercial food employs concerning amounts of such compounds and its human consumption must be avoided according Health Agencies. The purpose of this work was developing an alternative chromatographyc system based in commercial and common materials to be used to elucidate a experimental chromatographyc routine. Then, mixtures of sand (from river and sea) and starch were evaluated to achieve best separation of food dyes using ethyl alcohol, water and their mixtures. Figure 1 shows the column during dyestuff elution and each different color which can be seen. In addition to chromatography theory as well, discussions about molecular interactions, polarity and all steps in puification processes can enrich the class. Our first results showed good separation when food dyes containing amaranto, tartrazine and brilliant blue where submitted to this chromatographic column.