Science & Technology
Tests for Protein (Preliminary Test and Confirmatory Test)
Tests For Protein
Preliminary Tests for Protein
| Test | Experiment | Observation | Conclusion/Result |
Heating |
Slowly heated 2-3 ml of original solution in a test tube. | White precipitate formation | Proteins are present. |
Iodine Test |
Took 2-3 drops of original solution and then add a few drops of iodine solution. | The solution did not turns its color | Carbohydrates are absent |
Spot Test |
Poured one or two drops of original solution with the help of a dropper on a filter paper and allowed it to dry. | No greasy spot appeared on the filter paper | Lipids are absent |
Confirmatory Tests for Protein
| Test | Experiment | Observation | Conclusion/Result |
Million’s Test |
i) Took 2-3 ml of original solution and add 7-9 drops of Million’s reagent. ii) Prepared the same mixture and boiled | Formation of white precipitates Appearance of brick red color | Proteins are present Proteins are present |
Ninhydrin Test |
5 ml O.S. + 3 drops of 1% solution of ninhydrin in ethanol is added to 1 ml of the solution and the solution heated for five minutes in a boiling water bath. | formation of red, blue or purple color | Proteins are present |
Biuret Test |
2.5 ml original solution and add 2.5 ml of 5% of NaOH solution. Then mixed it by shaking thoroughly, and added 1-2 drops of 1 % copper sulphate solution and shake well. | Violet, red or pink color appeared | Proteins are confirmed |
By Prof. Imran Khan
