Millon's Test Practical Experiment

Summary

The Million's test is a chemical test used to detect phenols, specifically tyrosine-containing proteins, in biochemistry. The test involves adding a reagent with mercuric salts to samples and observing the formation of a pink to brick-red color if tyrosine is present. Although not specific to proteins, the Million's test is commonly used alongside other tests, like the Biuret or Ninhydrin tests, to confirm protein presence. The procedure includes reacting samples such as phenol, tyrosine, egg albumin, and starch with the reagent, with positive results indicating the presence of phenolic groups, particularly in tyrosine-rich proteins.

Takeaways

• 😀 The Millon's test is a chemical test used to detect phenols and phenol-containing compounds, particularly proteins with tyrosine.
• 😀 Tyrosine is the only amino acid containing a phenol group, making the Millon's test a general test for proteins.
• 😀 While the test detects phenolic groups, it is not specific to proteins and can identify non-protein phenolic compounds.
• 😀 To confirm the presence of proteins, other specific tests like the Biuret test and Ninhydrin test must also be performed.
• 😀 The Millon's test was invented by French chemist Auguste Nicolas Eugene Millon.
• 😀 The reagent for the Millon's test consists of mercuric salts or mercury dissolved in concentrated nitric acid.
• 😀 The principle behind the test involves nitration of the phenol group, forming colored complexes with mercury, especially with tyrosine.
• 😀 A positive Millon's test results in a pink to brick-red color in the presence of tyrosine or phenolic compounds.
• 😀 The test procedure involves adding samples (phenol, tyrosine, egg albumin, starch, and distilled water) into separate test tubes and adding Millon’s reagent.
• 😀 After mixing and waiting for a few minutes (or heating in a water bath), a positive reaction will show up as a pink or brick-red color in phenol, tyrosine, and egg albumin.
• 😀 The negative control (distilled water) and starch do not show any color change, confirming the test’s specificity to phenolic compounds.

Q & A

What is the Millon's test used for?

The Millon's test is primarily used to detect phenols and phenol-containing compounds. It has a broader application in biochemistry, particularly for detecting proteins that contain the amino acid tyrosine.

Why is the Millon's test considered a general test for proteins?

The Millon's test can be considered a general test for proteins because most proteins contain the amino acid tyrosine, which has a phenolic group that reacts in the test.

What limitation does the Millon's test have?

While the Millon's test can detect phenolic groups in proteins, it is not specific to proteins. It can also detect phenolic groups in non-protein compounds, which makes it necessary to confirm the presence of proteins using other tests like the Biuret test or the Ninhydrin test.

Who invented the Millon's test, and what is its origin?

The Millon's test was invented by French chemist Auguste Nicolas Eugene Millon, after whom the test is named.

What is Millon’s reagent composed of?

Millon’s reagent typically consists of mercuric salts or mercury metal dissolved in concentrated nitric acid.

What principle is the Millon’s test based on?

The Millon’s test is based on the principle of nitration of the phenol group in tyrosine, which forms a colored complex with mercury ions, typically resulting in a pink to brick red color.

How is the Millon’s test performed in a laboratory?

To perform the Millon’s test, samples of phenol, tyrosine, egg albumin, starch, and distilled water are placed in separate test tubes. Millon’s reagent is then added to each tube. After mixing and waiting for a few minutes, a color change to pink or brick red indicates a positive result.

Why does egg albumin show a positive result in the Millon’s test?

Egg albumin contains the amino acid tyrosine, which has a phenolic group. When treated with Millon’s reagent, the tyrosine in egg albumin forms a pink to brick red complex, indicating a positive result.

Why does starch not react in the Millon’s test?

Starch does not contain phenolic groups in its structure, so it does not react with Millon’s reagent and shows a negative result, which means it does not turn pink or brick red.

What should be done if no significant color change occurs after the Millon’s reagent is added?

If no significant color change occurs, the test tubes can be placed in a hot water bath for 1-2 minutes to promote the reaction and potentially observe the color change.