Paper Chromatography

How to Use Paper Chromatography in the Biology Classroom

 

Looking for a low-prep, high-impact lab to spark curiosity in your middle or high school biology students? 

👉 Paper chromatography might be the perfect fit. This classic experiment allows students to explore real-world applications of chemistry and biology through hands-on investigation. Whether you're introducing the scientific method, diving into molecular properties, or studying photosynthesis, chromatography is a versatile and visually rewarding lab to include in your curriculum.

 

What Is Paper Chromatography?

👉 Paper chromatography is a simple technique used to separate the components of a mixture. This method works by taking advantage of the varying solubilities and molecular weights of substances, allowing them to be identified based on how far they travel up a strip of paper in the presence of a solvent. In the real world, chromatography is an essential tool used in fields like forensics, toxicology, and pharmacology. Police labs use chromatography to detect drugs and toxins in blood and urine samples. By introducing this lab to your students, you're connecting them to important STEM career paths, and showing them science in action.

How Does It Work?

👉 The process is straightforward but packed with learning potential. A small dot or line of a sample (like ink or plant pigment) is placed near the bottom of a strip of chromatography paper. This strip is then placed vertically into a container with a shallow layer of solvent. As the solvent travels up the paper by capillary action, it carries the components of the mixture with it.

Here’s why the mixture separates:

• Solubility: More soluble substances dissolve better in the solvent and move farther up the paper.
• Molecular Weight: Smaller molecules tend to move more quickly than larger ones.
• Polarity: The cellulose in the paper is polar. More polar substances stick to the paper and don’t travel as far, while non-polar substances move more freely.

Chromatography Lab Ideas for the Biology or Physical Science Classroom

💧 Ink Separation

A fun and accessible introduction to chromatography is separating black ink from markers. Many black inks are actually mixtures of several colors. When placed in water, water-soluble inks spread apart into bands of dye. Not all markers will work the same way. Permanent inks may require rubbing alcohol or another solvent to separate. This gives students the opportunity to test variables and compare results across different solvents and ink types.

🍃 Plant Pigment Separation

This is a favorite in high school biology, especially during units on photosynthesis or plant biology. Students can extract pigments from leaves and discover that the color they see is actually a mix of chlorophyll-a, chlorophyll-b, xanthophyll, and carotene.

Fall is a perfect time to collect a variety of leaves from trees around your school. But if you’re teaching in winter, spinach leaves from the grocery store work just as well.

Materials You’ll Need

You don’t need a fancy setup to get started. Here's a basic chromatography kit:

• Chromatography paper (filter paper or coffee filters can work in a pinch)
• Small containers (test tubes, jars, or beakers)
• Solvents (water, rubbing alcohol, acetone, or other safe household solvents)
• Samples to test (leaves, markers, food dyes, etc.)
• Pencils, rulers, and scissors

 

Tip for teachers: Always test your materials and solvents in advance. Be sure to follow proper lab safety protocols, especially if using alcohols or other flammable substances.

What Solvent Should You Use?

The answer depends on the solubility of your sample. Water works well for many inks and food dyes. For permanent markers or plant pigments, isopropyl alcohol or acetone may be more effective.

Pro Tip: Encourage students to design their own investigations. They can test multiple solvents on the same type of ink or compare different brands of markers to determine which separates most clearly.

Why Use Paper Chromatography in the Biology Lab?

Paper chromatography gives students hands-on experience with:

• Designing and conducting controlled experiments
• Observing molecular behavior and physical properties
• Making qualitative and quantitative observations
• Connecting lab techniques to real-world applications

It’s also a visually exciting lab. Watching vivid colors separate into bands on a strip of paper never gets old, and makes for excellent lab notebook sketches!

Ready to Try It With Your Students?

If you're looking for classroom-ready chromatography labs, I have two student-tested resources that include everything you need: detailed procedures, printable lab handouts, answer keys, and grading rubrics.

🔬 Matter Lab Stations: Ink Separation – Perfect for introducing lab skills and the scientific method in both middle and high school.

🌿 Plant Pigment Chromatography Lab – Ideal for exploring photosynthesis and leaf pigments in your high school biology class.

Both labs are designed to save you prep time while providing meaningful, standards-based instruction. You can find them in my Teachers Pay Teachers store.