Investigation of Arsenic Limits in Pharmaceutical Analysis

This reaction of arsenic gas with hydrogen ion refers to the yellow patch of mercury chloride paper. The test is intended to demonstrate that the arsenic content does not exceed the individual monograph on grams per gram of test substance as it is the gram of the test substance.

Potassium iodide used as a minoriser. This is also called a Gutzeit test and requires special equipment. Arsenic limit values ​​are determined in ppm for each monograph. All reagents used should be as low as the content of the arsenic is possible.

Arsenic present in arsenic is reduced to arsenic acid by minimizing potassium iodide, tin acid, zinc and hydrochloric acid

Arsenic acid is further reduced by the hydrogen atom of arsenic gas and the mercury Chloroform paper to give a yellow spot

H3AsO4 + H2SnO2 —- H3As03 + H2SnO3

Arsenic acid Arsenic acid

H3AsO3 + 3H —— AsH3 + 3H2O

Arsenus acid Arsine

Determines the amount of yellow spot with mercury chloride

The equipment consists of a 100-ml glass jar that is sealed with a rubber plug. A 20 cm 5 mm glass tube passes through it.

The bottom of the tube is pulled by an inner diameter of 1.0 mm, a 15 mm opening and a diameter of 3 mm. Procedures for Arsenic Limits :

The test solution described in the single monograph must be prepared in the fermented flask

1 M potassium iodide and 10 g zinc AsT .

Assemble the appliance and immerse the flask in a water bath at about 40 ° C. C ensures homogeneous evolution of gas. The temperature can be adjusted to have a regular but not too violent evolution of gas.

The reaction may be increased by placing the apparatus in a warm surface as the mercury chloride paper has to be very dry during the test. After 40 minutes, any paint produced on mercury chloride is not as intense as diluting 1.0 ml of arsenic standard solutions (10 ppm As) in the same manner with 50 ml of water.

In successive tests, the tube is washed with 250 g / L hydrochloric acid, rinsed with water, and dried.

The solution is obtained by adding 10 ml of stagnant hydrochloric acid and 250 g / l of AsT and 1 ml of dilute arsenic acetate by the addition of 50 ml of water. The resultant solution, as described in the general assay, results in known coloration on mercury iodide paper known as ASR, known as standard coloring

  • Tin chloride is generally used for the full expansion of arzine
  • Zinc, potassium iodide as the reducing agent
  • Hydrochloric acid can be used to make acidic solutions.
  • Mercuric iodide papers are used to bind any hydrogen sulphide that can evolve along arzin


Arsenic compounds are very toxic, so you should take care of this test. It is very important and you need to know this.

Source by Ankur Choudhary

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