Paper Chromatography

Paper Chromatography

This week, students experimented with the chemistry technique known as chromatography, which separates particles in mixtures by size.  Variations of this technique are used in labs to separate and purify DNA, proteins, and other molecules for a wide range of experiments.  Our classes used paper chromatography to separate out the various colored dyes and pigments found in several different colors of markers.  First we talked about chemical mixtures and solutions, and then learned that inks are actually solutions of different pigments and dyes.

If an ink is hydrophilic, or “water-loving”, it’s pigments and dyes will dissolve in water or in other solvents that are polar like water is, while hydrophobic inks “water fearing” will dissolve in nonpolar solvents.   The solvents used in class were water (a polar solvent, which dissolves the inks used in Crayola markers) and rubbing alcohol (a moderately nonpolar solvent, which also dissolves the inks used in permanent markers like Sharpies).

We found that there are different mixtures used by different companies  (Crayola and Rose Art) to produce “black” markers.   It is very interesting to see the different color separations from the markers, particularly the differences between different brands or types of the same color marker!

This is actually a great experiment to continue at home; all you need are markers, filter paper (coffee filters or paper towels work just fine), a solvent (rubbing alcohol or water), and a way to hang the paper so that just one end dips into the solvent. We clipped our papers to a pencil using small binder clips and then hung them on a container with a bit of rubbing alcohol in the bottom.


Cromatografía en Papel

Esta semana, los estudiantes experimentaron con una técnica de la química denominada cromatografía. Esta técnica se utiliza en los laboratorios para separar y purificar ADN, proteínas y otras moléculas en variados tipos de experimentos. Nuestros alumnos utilizaron la técnica de cromatografía en papel, para separar los diversos tintes y pigmentos que se encuentran en rotuladores (“markers”) de colores. Durante la clase, primero conversamos sobre mezclas de sustancias químicas y soluciones, y luego sobre la tinta de los rotuladores, la cual es una solución compuesta por diferentes pigmentos y colorantes.

Si una tinta tiene la característica de ser hidrofílica, es decir que “les atrae el agua”, los pigmentos y colorantes que la componen se disolverán en agua o en otros solventes que son polares (como el agua. En cambio, si la tinta es hidrofóbica o “que le repele el agua”, se disolverá en solventes no polares. En la clase se usaron como solventes: agua (solvente polar, el cual disuelve la tintas utilizada en los rotuladores de marca Crayola) y alcohol (un solvente relativamente no polar, el cual disuelve la tinta de los rotuladores permanentes como los de marca Sharpie).

Después de hacer los experimentos, hallamos que distintas marcas de rotuladores (Crayola y Rose Art), utilizan diferentes mezclas para producir los rotuladores de color negro. Fue muy interesante observar cómo la tinta se separaba en distintos colores y apreciar que existen diferencias entre las distintas marcas y tipos de rotuladores de un mismo color.

Este tipo de experimento, es una excelente actividad para ser continuada en casa. Sólo necesitas rotuladores, papel filtro (filtros de café o toallas de papel absorbente también funcionan), solventes (agua o alcohol) y algo para sujetar el papel para que solo un extremo del papel sea sumergido en el solvente. Nosotros pusimos un clip al papel y luego sujetamos con un lápiz el clip y colgamos los papeles sobre un contenedor con un poco de alcohol.


Lauren Koppel

Lauren earned a Bachelor’s degree with a double major of Biology and Psychology from Clark University, and a Master of Education from the Harvard Graduate School of Education. During her undergraduate years, she worked in a evolutionary neurobiology lab that studied the neural development of annelids (marine worms), with a focus on the sox family of genes. Lauren loves learning about how the world works (including everything from biology to chemistry to engineering), and is passionate about sharing that knowledge and enthusiasm with others. In the past, she has interned at the Museum of Science, where she educated learners of all ages through hands-on activities, games, and experiments. Other science education organizations with which Lauren has worked include The People’s Science, EurekaFest, and Eureka! of Girls Inc. of Worcester. Currently she lives in Boston, where devotes her free time to playing Quidditch, reading sci-fi novels, playing her ukulele, and enjoying all the culinary delights the city has to offer.

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Our Young Pre classroom is for ages. This age group is working