Archive for the ‘Reagents’ Category

Mayer’s Reagent

Monday, July 7th, 2008

Mayer’s Reagent & It’s Reaction with Alkaloids

Used for the detection of alkaloids in natural products.

Mayer’s reagent is freshly prepared by dissolving a mixture of mercuric chloride (1.36 g) and of potassium iodide (5.00 g) in water (100.0 ml).

Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer’s reagent (potassiomercuric iodide solution) to give a cream coloured precipitate.

The Dragendorff Reagent

Wednesday, October 31st, 2007

Dragendorff Reagent:

TLS Sprayed With Dragendorff Reagent

The Dragendorff’s Reagent is used for the detection of Nitrogenous compounds, alkaloids, antiarrhythmic drugs and surfactants and is also good detector for Phenols.

There are two kinds for preparations, each procedure says preparation of Solution A and Solution B, both are then mixed to use.

1st Method:

Solution A: 1.7 g basic bismuth nitrate in 100 ml water/acetic acid (4:1).

Solution B: 40.0 g potassium iodide in 100 ml of water.

Mix reagents together as follows: 5 ml A + 5 ml B + 20 ml acetic acid + 70 ml water.

Spray plates, orange spots develop. Spots intensify if sprayed later with HCl, or 50% water-phosphoric acid. Good for phenols.

2nd Method:
Solution A: 1.7 g basic bismuth nitrate and 20 g tartaric acid in 80 ml of water.
Solution B: 16 g potassium iodide in 40 ml of water.

Stock solution: (stable several weaks in a refrigerator): mix equal volumes of solutions A and B
Procedure: Spray with a solution of 10 g tartaric acid, 50 ml water & and 5 ml stock solution.