Orange Green Blue Red Black Unknown Known In the experiment, the solvent travels up the paper. The dyes on the pencil line dissolve in the solvent. The more soluble the dyes are in the solvent, the faster they move up the paper. So the dyes move up the paper at different speeds. Hence the dyes are separated. Colored Spot
Identical dyes travel the same distance up the paper. The unknown dyes in the black ink can be identified by comparing them with known black dyes. The result of the experiment show that
Black ink is made up of 4 different dyes.
Three of the dyes are known. They are Red , Blue and Green dyes.
There is no Orange dye in the black ink.
Black ink consists 1 dye that is different from the four known dyes.
Paper Chromatography – Chromatogram
Which of the soft drinks contain a harmful dye? A) P and Q B) R and S C) Q and S D) P and R P Q R S X Y soft drinks dyes Interpreting Chromatograms
What can be done if the substance is colourless ?
Use ultraviolet (UV) light to see the components. Many substances are coloured under UV light but colourless in white light.
Use a locating agent (eg ninhydrin solution). Ninhydrin solution forms a purple stain with amino acids (colourless).
The agent will react with the substances on the paper to form a coloured product .
chromatography What happen if there are more than 20 suspected substances in the sample? It would not be practical to put all the suspected substances on the chromatogram. We can make use of the R f values.
It is easier and more sensible to - measure the R f value of each component and then identify them by looking at known R f in reference book. R f value = Distance travelled by the substance Distance travelled by the solvent
Identify a compound by spotting known substances next to unknown substances on the same chromatogram.
Determine purity of a sample. An impure sample will often develop as two or more spots, while a pure sample gives only one spot.
To detect colorless liquids, a locating agent may be sprayed onto the chromatogram.
Locating agent : chemical that reacts with the substance to produce a visibly coloured product. Example: ninhydrin that reacts with colourless amino acids to produce a purple stain .
Drugs have provided the world of athletics with a fierce opponent ever since the emergence of systematic forms of doping in eastern Europe. But the most famous case in history is that involving a westerner - Canadian sprinter Ben Johnson. He won the 100 metres at the 1988 Seoul Olympics in a world record time but was later stripped of his gold medal and banned for two years after testing positive for an anabolic steroid. Since then he has made an unsuccessful attempt to get back into the Canadian team for the 2000 Olympics. There have also been some bizarre stunts such as a race with two horses and car for charity. The animals beat him although the car was stalled by wheelspin. Johnson has recently worked as personal fitness trainer for footballer Said Gaddafi, son of Libyan president Colonel Muamar Gadaffi. Meanwhile an incident in which a mugger took his wallet and outran him showed that the 38-year-old does not have the speed he once possessed. Drugs in world athletics BBC Sport website (Mon 31 July 2000) Tainted win: Johnson (second left) wins in Seoul A life ban from the track followed in March 1993 when he gave another positive test.