Limit Test For Arsenic In Pharmaceutical Analysis

This is based on the reaction of the arsenic gasoline with hydrogen ion to a yellow stain of mercuric chloride paper’ The test is offered to show that the content material of arsenic does not exceed the limit given the individual monograph in terms of arsenic per gram of the test substance’


Potassium iodide used as a lessening agent’ It is additionally known as the Gutzeit test and a special equipment is required’ The limit for arsenic is indicated in the individual monographs in terms of ppm’ All reagent used should be as low as a content material of arsenic as possible Monografias Prontas


Arsenic which is present as arsenic in the flavor is reduced to arsenious acidic by minimizing brokers just like potassium iodide, stannous acid, zinc and hydrochloric acid’


The arsenous acid is additional lowered to arsine gasoline by hydrogen and reacts with mercuric chloride paper to give a yellow stain’


H3AsO4 + H2SnO2 ­­-­­­­— H3As03 +H2SnO3′


Arsenic acid Arsenous acid’


H3AsO3 + 3H —— AsH3 + 3H2O’


Arsenous acid Arsine


The quality of arsenic present in the same will investigate the amount of the yellow stain on the mercuric chloride’




They consist of a one hundred ml bottle of conical flask closed with a floor rubber stopper’ A glass tube of about 20 cm by 5mm passes through it’


The lower part of the tube is drawn to an inside diameter of 1’0 mm, a lateral orifice of 15 mm from its advertising and three mm in diameter’


strategies for limit test for arsenic:


Introduce the test solution arranged as directed in the individual monograph into the conical flask’


Add 5 ml of 1M potassium iodide and 10 g of zinc AsT’


bring to a standstill the equipment and immerse the flask in a water bath at a temperature of about forty deg’ C to be sure that a homogenous evolution of a fuel is maintained’ The temperature may be adjusted to accomplishing a regular however not too violent evolution of the gas’


The reaction may be extreme temperature by tormented by the equipment on a warm floor, care being taken for the mercuric chloride paper to remain quite dry across the test’


After forty minutes any stain produced on the mercuric chloride, the paper is not more extreme than that received by treating, in the same demeanour, 1’0 ml arsenic standard answers (10 ppm As) diluted to 50ml with water’


among successive exams, the tube afford be washed with hydrochloric acid (250 g/l) AsTS, rinsed with water and dried’


Standard Stain


accomplishing by instruction of a solution by including 10 ml of stagnated hydrochloric acid and (250 g/l) AsTs and 1ml of dilute arsenic AsTs, to 50 ml of water’ The resulting solution, when handled as defined in the average test, yield a stain on the mercuric iodide paper as ASR, Known as the Standard Stain’




Stannous chloride is generally used for full growth of arsine’

Zinc, potassium iodide are used as deadline agents’

Hydrochloric acid is used as a tool to make the solution of acidic’

Mercuric iodide papers are used to captivating any hydrogen sulphide which may be developed alongside the arsine’



Arsenic compounds are very poisonous and care should be taken when coping with this test’ It really important and should be conscious of this’