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What is the limit test for heavy metals in pharmaceuticals?

The limit test of heavy metals in pharmaceuticals indicates the number of heavy metals present as drug impurities. Heavy metals' presence is expressed in the quantity of lead. These are the metallic inclusions darkened with sodium sulphide in a hydrogen sulphide-saturated solution. The leading labs for Metal testing in Chennai carry out this test on metals like lead, mercury, bismuth, arsenic, antimony, tin, silver, copper Pb) etc. The presence of impurities is presented as parts of lead (per million parts of the substance or ppm. According to Indian Pharmacopoeia, 20 ppm is the limit of impurities in heavy metals.

Apparatus needed for limit test

  • Nessler cylinders

  • Glass rod

  • Stand

Chemicals required for test

  • Dilute CH3COOH (10% v/v)

  • Dilute ammonia (10% v/v)

  • Hydrogen sulphide solution 

  • Standard lead solution 

  • Lead nitrate stock solution

Test procedure

The leading Metal Inspection & Analysis Testing in Chennai suggests the following method for the limit test of heavy metals. 


Test

Standard

Solution is prepared according to the monograph and 25 ml is transferred to the test cylinder

2 ml of lead solution is diluted with 25 ml of water


The pH is adjusted between 3 to 4 by adding acetic acid or ammonia solution

The pH is adjusted between 3 to 4 by adding acetic acid or ammonia solution

After diluting it with water up to 35 ml, 10 ml Hydrogen sulphide solution is added

After diluting it with water up to 35 ml, 10 ml Hydrogen sulphide solution is added

Dilute with water to make it 50 ml and allow to stand it for a few minutes

Dilute with water to make it 50 ml and allow to stand it for a few minutes

Observe the amount of the black precipitation of lead sulphide and compare it with the standard. 


Observe the amount of the black precipitation of lead sulphide and compare it with the standard. 




At Test House, one of the best labs for Metal testing in Chennai, we carry out limit tests for various metals to determine the quantity of metallic impurities. To know more, contact us now.


Ref


https://solutionpharmacy.in/limit-test-for-heavy-metals/


https://www.web-formulas.com/Formulas_of_Chemistry/Limit_Test_of_Heavy_Metals.aspx
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