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What Is Paper Chromatography and How Does it Work?

What Is Chromatography?

Chromatography is a method for separating the parts of a mixture of either a gas or liquid solution containing different chemicals. For example, pen inks are often made up of different colours. The different bonding properties of each molecule type is exploited. Chromatography is used in both qualitative and quantitative analysis of both organic and inorganic samples. This technique uses two types of substances:

  1. Mobile phase: a gas or liquid that transports the solution being tested through the other substance (water, rubbing alcohol are examples).
  2. Stationary phase: the liquid or solid through which the tested substance is carried (coffee filter paper, paper towel are examples).

It is necessary for the different chemicals in the solution fo have different properties such as molecule size or a different ability to dissolve in a solvent. The stationary phase will absorb or slow down different components of the tested solution to different degrees creating layers as the components of the solution are separated. Chromatography was invented by the Russian botanist, Mikhail Tsvet. Chemists use this process to identify unknown substances by separating them into the different molecules that make them up.

How Does Paper Chromatography Work?

Chromatography can be demonstrated using a simple demonstration.

What you need:

  • water soluble pens or markers of different brands or colours
  • strips of paper towel
  • water
  • rubbing alcohol
  • nail polish remover
  • straw or pencil or pen
  • cups
  • tape

What you do:

  1. Draw a line across 6 paper towel strips or coffee filter strips about 1 inch from the bottom.
  2. Tape the paper towel strip from the end opposite to the pen line onto the middle of the straw so the strip will hang when the straw is placed crosswise onto the cup.
  3. There should be enough water in the cup so that the paper towel strip touches the water but the pen line is NOT submerged.
  4. The strip should not touch the bottom of the cup.
  5. If using alcohol or nail polish remover as all or part of your solvent, place a cap of aluminum foil over the glass to keep the vapours in the glass. It will improve the results.
  6. Observe what happens.
  7. If the pen line remains unchanged in water, try with the same pen type on another strip of paper towel but substitute the alcohol or nail polish remover.
  8. Try mixing one half water and one half alcohol as your solvent and see how the colours separate.

What's Happening in Paper Chromatography?

Ink is a solution containing a number of different molecules. These different molecules have different characteristics such as size and solubility. Solubility is a molecule's ability to dissolve in a particular solvent such as alcohol, water or nail polish remover. Because of their different characteristics, each molecule travels at a different speed when pulled along the piece of paper towelling by the solvent. The lightest particles, which are not necessarily the lightest coloured particles, move more quickly and a greater distance than the heavier particles. Thus, all of the pigments that make up an ink sample are separated out.

Chromatograph of Black Ink

This chromagraph of black ink used rubbing alcohol as a solvent. Comparing a chromatogram made with the same solid medium and solvent, a comparison can be made to determine the type and brand of ink used at a crime scene.

This chromagraph of black ink used rubbing alcohol as a solvent. Comparing a chromatogram made with the same solid medium and solvent, a comparison can be made to determine the type and brand of ink used at a crime scene.

Applications of Paper Chromatography

Chromatography is used in chmistry in a number of applications:

  1. Unknown substances left at a crime scene can be identified by separating the molecules that make them up. Matching this unknown chromatogram to chromatograms of known substances can help identify the unknown substance providing a clue to the crime.
  2. The ink used in a note left at a crime scene can be identified through paper chromatography. The chromatogram showing the components of the ink used in the note can be compared to chromatograms of known inks hopefully identifying the type and brand of ink used providing a clue to the crime.
  3. It is used in the sequencing of DNA and RNA.
  4. Paper chromatography is used as a qualitative analytical chemistry technique for identifying and separating colored mixtures like pigments.
  5. It is used in scientific studies to identify unknown organic and inorganic compounds from a mixture.
  6. In order to obtain a pure sample each component of the separated mixture, the separated spots on the finished and dried chromatogram can be cut out and re-dissolved.

Works Cited

Uses of Paper Chromatography. Tutor Vista.com. 2010.

Chromatography. Asistm Forensic Investigations.

Cook, Trevor. Experiments with States of Matter. New York: Power Kids Press, 2009.

Questions & Answers

Question: What is a paper chromatography's mixture?

Answer: Usually rubbing alcohol is used as a solvent to separate colors of ink.

Comments

prisha on July 18, 2020:

which are the two examples oof paper chromatography?

pls help

holie on December 04, 2019:

if your dye is soluble in water why did they separated

Jhoan on August 11, 2019:

What is the use of filter paper?

Anas on July 21, 2019:

I understand it very well and I am now experimenting it

jason bourne on March 11, 2019:

will this help me identify what chemicals were used in crime scene?

sammy on February 03, 2019:

which is better to use, filter paper or paper towel? and why?

Mohammed on October 18, 2018:

When was this published?

Meow on October 05, 2018:

Thanks I am doing an experiment for science fair with my partner and we chose paper chromatography! thanks so much for this information!

Teresa Coppens (author) from Ontario, Canada on August 22, 2018:

Happy to hear that Sofia!

Sofia on August 19, 2018:

I understand it very well

angel on June 07, 2018:

I understand about Chrmatography

Sherece on May 26, 2018:

I understand thank u

Rebekah on April 15, 2018:

Thank you very much for helping!!

rejo on February 19, 2018:

Anx a lot but what is another type of chromatography and how to define the changes of liquids on the chromatography

rex on February 18, 2018:

thank you

online tutoring on January 17, 2018:

Thnx

Luna on January 10, 2018:

Useful, thx!

Bigey on October 18, 2017:

Very useful, thank you!

Sathwika on September 08, 2017:

Super

mridul bansal on August 30, 2017:

this is a very useful information for a child to understand that what is chromatography. but if there would be more pictures related to the steps then it would me more understandable and easy. if there would be a video also then i am sure that this page is liked by all. some better steps are also required. this information is very simple to understand by a 9th class standard student but if a 8th class or below student want to understand that what is chromatography then he could not understand from only this much information . i prefer you to add more videos images at every step and more information to this project.

Ana on August 29, 2017:

Needs to be a clearer explanation of how it works.

Aina on August 05, 2017:

Very useful thank you soon much

William on July 10, 2017:

I need a help about a research of chromatography

mehreen prri on June 09, 2017:

what is chromatography and explain about it.

Tamiyah Maupin on May 15, 2017:

I need a answer to this question without the experiment stuff What is chromatography when it come to dying materials

Syedshayan on April 28, 2017:

Nice work mam

Someone Who Needs A Big Brain on April 13, 2017:

Agh,thanks for all the info but.. what method is Paper Chromatography used in

Annabeth (yes that is my real name, not from Percy Jackson) on March 31, 2017:

Thanks so much for posting this article Teresa Coppens, I am doing a research paper and this has helped me so much. I have cited this site for my research paper, I have checked other rescources and site, of all of them yours is the most helpful and easy to understand. I also successfully completed the experiment. Once again thank you SO MUCH!! This is a great experiment for 6th graders!

Scienceisawesome on March 20, 2017:

Thanks, this has helped me with my science research.

This article has helped me understand chromatography more easily.

Thanks a lot!

suck my on March 19, 2017:

thanks this really helped my science homework out a lot and it could use a bit more info, but overall this was totally helpful

Teresa Coppens (author) from Ontario, Canada on February 15, 2017:

Jhen so sorry. I'm not often on this site any longer. Capillary action is the answer to question one. Question 2 was answered in the article. Different colors molecules within the dye move based on weight. Lighter molecules travel faster while heavier ones travel slower. Weight is determined by the molecular formula of the molecule.

Jhen on October 28, 2016:

I haven't gotten an answer and I need it for my lab!!!! Omg! 1)What process did the water move up the filter strip?2)what factors determine the rate at which the dye move up the filter paper?

Teresa Coppens (author) from Ontario, Canada on October 23, 2016:

I am so glad it worked well for you. I love it that it inspired your siblings!

Teresa Coppens (author) from Ontario, Canada on October 23, 2016:

You'll need to use the updated date which is indicated on the hub.

Teresa Coppens (author) from Ontario, Canada on October 23, 2016:

Glad I could be of assistance.

Teresa Coppens (author) from Ontario, Canada on October 23, 2016:

Glad it helped you out.

Teresa Coppens (author) from Ontario, Canada on October 23, 2016:

Glad it helped!

Linley on October 11, 2016:

Very helpful! I am doing a science fair project about paper chromatography and this is just what I was looking for! After I read this article, I performed the experiment right away. It worked very well and my siblings were crowding around me to watch. After that, they started to do the experiment as well! This is an exciting project for all ages and it has interested me very much! Thank you!!

Shel on September 28, 2016:

When was this published I'm writing a bibliography and this is a great source so I would appreciate it if you could inform me of when it was published. Thank you

... :P on September 26, 2016:

Thanks so much! This really help for my science homework!!!

nerd on September 25, 2016:

What is the best definition for affinity?

nerd on September 20, 2016:

thnx, this helped a lot for science fair

wouldn't have done it without you

Rakesh Kumar on May 18, 2016:

Its so helpful for us thnxxx.

reach alex uganda on October 21, 2015:

describe how you would perform each one of the forms of chromatofraphy

connor on April 27, 2015:

very helpful for science fair thanks!

Teresa Coppens (author) from Ontario, Canada on April 09, 2015:

Thanks Tolova. I do my best to make science easy to understand.

Teresa Coppens (author) from Ontario, Canada on April 09, 2015:

I hope it was helpful.

Tolovaj Publishing House from Ljubljana on April 02, 2015:

TLC is important analytical method for every researcher. It's not the most reliable, but it's fast and very useful at repetitive reactions, when you want just a quick check if everything in the reactor works like it supposed to. You made very clear presentation of the method. Well done:)

Unknown on February 27, 2015:

thanks, it was for my homework;)

shak on February 05, 2015:

This information was very helpful for me in doing my chemistry lab

Teresa Coppens (author) from Ontario, Canada on July 04, 2014:

Sorry for the long time for a reply. Glad the article helped. Hope you did well.

Tresha on February 09, 2014:

I had to write a lad report and I used a lot of information from this article. Thank you so much

Teresa Coppens (author) from Ontario, Canada on November 11, 2013:

Thanks for commenting Sarah. Hope you found the article useful.

sara donya on November 10, 2013:

it is good

Teresa Coppens (author) from Ontario, Canada on June 18, 2013:

So glad you found this useful! Cheers Aslam

Aslam on June 17, 2013:

Useful

Teresa Coppens (author) from Ontario, Canada on June 06, 2013:

Hey Mel. Glad to hear from you again. I have done this lab a few times in the past with high school kids. Looking forward to teaching another course where I can use it again. The technique does have a wide range of applications. Glad you enjoyed the hub. Good luck in your studies!

Melanie from Midwest, USA on June 06, 2013:

I had a chemistry lab last semester on both paper and TLC chromatography. The paper lab done was using different eluents to see which was the most effective (we used a Sharpie dot on the paper.)

The TLC lab was a row of different analgesic drugs and then a mystery drug made up of one or more of the known drugs. We had to find out the mystery drug based on how the results compared to the known drugs. It was a pretty awesome lab... probably my favorite, actually.

Awesome hub! Brings back a fun memory!