Method of Analysis for Erythrosine Supra Colour

Description:

A pink coloured powder.

Solubility:

Freely soluble in water and in dilute acids & in dilute alkali.

Identification:

By Assay: The final solution obtained in the assay gives maximum absorbance at 428 nm.

pH:

Weigh 1.0 g of the sample in 100 ml volumetric flask and dissolve in water to produce 100 ml with water, and check the pH of these solutions.

Limit: 5.00 to 8.50

Heavy metals:

Standard solution: Into a 50 ml Nessler cylinder pipette 1.0 ml of lead standard solution (40 ppm pb) and dilute with water to 25 ml. Adjust with dilute acetic acid or dilute ammonia solution to a pH between 3.0 and 4.0 dilute with water to about 35 ml, and mix.

Test solution: Weigh 1.0 g in a suitable crucible, add sufficient sulphuric acid to wet the sample, and ignite carefully at a low temperature until thoroughly charred. Add to the charred mass 2 ml of nitric acid and 5 drops of Sulphuric acid and heat cautiously until white fumes are no longer evolved. Ignite, preferably in a muffle furnace, at 500° to 600°C, until the carbon is completely burnt off. Cool, add 4 ml of hydrochloric acid, cover, digest on a water bath for 15 minutes, uncover and slowly evaporate to dryness on a water bath. Moisten the residue with 1 drop of hydrochloric acid, add 10 ml of hot water and digest for 2 minutes.

Add Ammonia solution to dropwise until the solution is just alkaline to litmus paper; dilute to 25 ml with water and adjust with dilute acetic acid to a pH between 3.0 and 4.0. filter, if necessary, rinse the crucible and the filter with 10 ml of water, combine the filtrate and washings in a 50 ml Nessler cylinder, dilute with water to about 35 ml and mix.

Procedure: To each of the cylinders containing the standard solution and test solution, respectively, add 10 ml of freshly prepared hydrogen sulphide solution. Mix, dilute to 50 ml with water, allow to stand for 5 minutes and view downwards over a white surface; the colour produced with the test solution is not more intense than that produced with the standard solution.

Limit: NMT 40ppm.

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Arsenic:

Dissolve 5.0 g. in 10 ml of bromine solution and evaporate to dryness on a water – bath. Ignite gently, dissolve the cooled residue, ignoring any carbon, in 50 ml of water and 14 ml of brominated hydrochloric acid AsT, and remove the excess of bromine with a few drops of stannous chloride solution AsT.

Into the bottle or conical flask, introduce the test solution prepared as directed above; add 5 ml of 1 M potassium iodide and 10 g of zinc AsT. Immediately assemble the apparatus and immerse the flask in a water bath at the temperature such that a uniform evolution of gas is maintained. After 40 minutes any stain produced on the mercuric chloride paper is not more intense than that obtained by treating in the same manner 1 ml of arsenic standard solution (10 ppm As) diluted to 50 ml with water.

Limit: NMT 3 ppm

Water In-soluble Matter:

Weigh accurately about 2 g of sample and shake with 100 ml of distilled water for 5 minutes and filter through sintered glass crucible G4 (previously dried & weighed). Dry the crucible at 105℃ to a constant weight and find out the weight of insoluble matter.

Calculation:

Limit: NMT 0.5%

Loss on drying:

Place the 1 g of the substance to be examined in a weighing bottle previously dried under the conditions. Dry the substance for the 2 hours in 110℃. After drying, the sample cooled in desiccators, and the bottle was weighed.

Weight of weighing bottle = ____________ g (A)
Weight of weighing bottle + sample = ____________ g (B)
Weight of sample (B-A) = ____________ g (C)
Weight of weighing bottle + sample = ___________g (D) (After drying at 110 ℃. for 2hrs)
Loss in weight (B-D) = ________________ g (E)

Limit: NMT 20.0%

Total dye content:

Weigh accurately about 100 mg of the sample and transfer into a 200 ml volumetric flask. Add 20 ml of water and dissolve. Make up the volume with the same water. Dilute 2.0 ml to 100.0 ml with the same solvent. Read the absorbance of the final solution at 527 nm using water as a blank. Calculate the assay taking the value of A1% 1080.

Calculation: