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Basic Tests for Drugs - Pharmaceutical Substances, Medicinal Plant Materials and Dosage Forms
(1998; 100 pages) [French] [Spanish] View the PDF document
Table of Contents
View the documentPreface
View the document1. Introduction
View the document2. Other collections of simple tests
View the document3. Test procedures for pharmaceutical substances
View the document4. Test procedures for medicinal plant materials
View the document5. Test procedures for pharmaceutical dosage forms
View the document6. Reagents
View the documentAcknowledgements
View the documentOther WHO publications on pharmaceuticals
View the documentBack cover
 

3. Test procedures for pharmaceutical substances

AMIKACIN SULFATE

Identity tests

Description. A white to yellowish white, crystalline powder; almost odourless.

Colour and other reactions

1. Dissolve 10 mg in 1 ml of water, add 1 ml of sodium hydroxide (~80 g/l) TS and mix, then add 2 ml of cobalt(II) nitrate (10 g/l) TS; a violet colour is produced.

2. Dissolve 0.05 g in 3 ml of water and add slowly 4 ml of anthrone TS; a bluish violet colour is produced.

3. Dissolve 20 mg in 1 ml of water and add 1 ml of barium chloride (50 g/l) TS; a white precipitate is produced which is practically insoluble in hydrochloric acid (~250 g/l) TS.

BACITRACIN ZINC

Composition. Bacitracin zinc is a zinc complex of bacitracins, polypeptides produced by the growth of an organism of the licheniformis group of Bacillus subtilis. The main components are the bacitracins A, B1 and B2.

Identity tests

Description. A white or pale brownish yellow powder; odourless or with a faint, characteristic odour; hygroscopic.

Colour and other reactions

1. Shake 5 mg with 1 ml of water, add 1 ml of triketohydrindene/butanol TS and 0.5 ml of pyridine R and heat to 100°C for 5 minutes; a violet colour is produced.

2. Transfer about 0.5 g to a silica crucible and ignite. Dissolve the residue in 5 ml of sulfuric acid (~5 g/l) TS and filter. Divide the filtrate into 2 equal volumes.

(a) To 1 volume add 1 ml of potassium ferrocyanide (45 g/l) TS; a white precipitate is produced which is insoluble in hydrochloric acid (~250 g/l) TS.

(b) To 1 volume add 1 drop of copper(II) sulfate (1 g/l) TS and 1 ml of ammonium mercurithiocyanate TS; a violet precipitate is produced.

Degradation tests

Discoloration of the test substance and non-compliance with the following test usually indicate gross degradation:

Dissolve 0.10 g in 100 ml of water; a clear, colourless or slightly yellowish solution is produced.

CAPTOPRIL

Identity tests

Description. A white or almost white, crystalline powder; odour, characteristic but faint.

Colour and other reactions

1. Dissolve 10 mg in 2 ml of hydrochloric acid (0.1 mol/l) VS and add about 1 ml of iodine TS; the colour of the iodine disappears immediately and a white, turbid solution is produced.

2. Dissolve 10 mg in 2 ml of water and add 0.5 ml of lead acetate (80 g/l) TS; a white precipitate is produced.

3. Dissolve 10 mg in 5 ml of ethanol (~750 g/l) TS, add 0.5 ml of tetramethylammonium hydroxide/ethanol TS and shake. Then add 0.5 ml of triphenyltetrazolium chloride/ethanol TS and shake again; a red colour is produced.

CHLORAMPHENICOL SODIUM SUCCINATE

Identity tests

Description. A white or almost white powder; hygroscopic.

Colour and other reactions

Dissolve about 1.4 g in 5 ml of water and use as the test solution for the following tests:

1. To 1 drop of the test solution add 5 ml of ethanol (~750 g/l) TS, 0.2 g of zinc R powder and 1 ml of sulfuric acid (~100 g/l) TS and allow to stand for 10 minutes. Filter; to the filtrate add 0.5 ml of sodium nitrite (10 g/l) TS and allow to stand for 2 minutes. Then add about 1 g of urea R and a solution containing 10 mg of 2-naphthol R in 2 ml of sodium hydroxide (~80 g/l) TS; a red colour is produced.

2. Repeat test 1 omitting the zinc R powder; no red colour is produced.

3. Carefully heat 1 drop of the test solution with 10 mg of resorcinol R and 3 drops of sulfuric acid (~1760 g/l) TS, cool and add 2 ml of water. Cool again and pour the solution into a mixture of 100 ml of water and about 1 ml of sodium hydroxide (~400 g/l) TS; a yellow-green fluorescence appears which disappears on the addition of 1 ml of hydrochloric acid (~250 g/l) TS.

4. Introduce the test solution into a non-luminous flame using a magnesia stick or a nichrome or platinum wire sealed to a glass rod; the flame acquires an intense yellow colour.

Degradation tests

Discoloration of the test substance and non-compliance with the following test usually indicate gross degradation:

Dissolve 0.2 g in 10 ml of water; a clear solution is produced.

CISPLATIN

Identity tests

Description. White to yellowish crystals or a yellow powder.

Note. This substance is very toxic and should be handled with care.

Colour and other reactions

1. Dissolve 5 mg in 5 ml of hydrochloric acid (~420 g/l) TS and heat to boiling. To half of the solution (keep the unused portion for test 2) add a few crystals of potassium iodide R; a brownish yellow colour is produced which changes to reddish brown on standing.

2. To the remaining solution from test 1 add a few crystals of tin(II) chloride R; a reddish orange colour is produced which changes to reddish brown on standing.

3. Transfer 0.05 g to a glass dish and add 2 ml of sodium hydroxide (~80 g/l) TS. Evaporate to dryness and dissolve the residue in a mixture of 0.5 ml of nitric acid (~1000 g/l) TS and 1.5 ml of hydrochloric acid (~420 g/l) TS. Again evaporate to dryness; an orange-coloured residue is produced. Dissolve the residue in 0.5 ml of water and add 0.5 ml of ammonium chloride (100 g/l) TS; a yellow, crystalline precipitate is produced.

COAL TAR

Composition. Coal tar is a by-product usually obtained during the destructive distillation of coal. It is a complex and undefined mixture of a great number of chemical compounds. The product is available in various compositions.

Identity tests

Description. Brown-black or black, viscous liquid; odour, characteristic and strong, resembling naphthalene. On exposure to air the liquid solidifies.

Heating behaviour. When ignited, the liquid burns in air with a luminous sooty flame and almost no residue remains.

Colour and other reactions

1. Shake 1 drop vigorously with 5 ml of ethanol (~750 g/l) TS and filter; the filtrate is yellow with a bluish green fluorescence.

2. Shake about 1 g vigorously with 9 ml of water for 10 minutes and filter; the filtrate gives a neutral or only slightly acid reaction when tested with litmus paper R (unlike wood tar) and an odour of naphthalene is discernible (keep the filtrate for test 3).

3. To 5 ml of the filtrate from test 2 add a few drops of bromine TS; a yellow turbidity develops (phenols).

Degradation test

If the substance does not pass the following test, this usually indicates that gross degradation has occurred:

Dissolve 0.10 g in 10 ml of nitrobenzene R; a clear or almost clear solution is produced.

DOXORUBICIN HYDROCHLORIDE

Identity tests

Description. A red-orange, crystalline powder; hygroscopic.

Note. This substance is very toxic and should be handled with care.

Colour and other reactions

1. Place a small quantity of the test substance on a white test plate and add 1 drop of formaldehyde/sulfuric acid TS; the orange-red colour of the substance changes to violet.

2. Dissolve about 2 mg in 2 ml of methanol R and add 2 ml of water and 1 drop of sodium hydroxide (~80 g/l) TS; the orange-red colour of the solution changes to blue-violet.

3. Dissolve 0.05 g in 1 ml of water, add 5 drops of ammonia (~100 g/l) TS and filter. Acidify the filtrate with nitric acid (~130 g/l) TS and add 1 ml of silver nitrate (40 g/l) TS; a white, curdy precipitate is produced which is soluble in ammonia (~100 g/l) TS but practically insoluble in nitric acid (~1000 g/l) TS.

FLUPHENAZINE DECANOATE

Identity tests

Description. A pale yellow, viscous liquid or a yellow, crystalline solid with an oily appearance; odour, faint and ester-like.

Colour and other reactions

1. Dissolve 5 mg in 2 ml of sulfuric acid (~1760 g/l) TS and allow to stand for 5 minutes; a reddish brown colour is produced.

2. Dissolve 5 mg in about 2 ml of formaldehyde/sulfuric acid TS; an orange colour is produced. Heat in a water-bath for 2 minutes; the colour changes to dark brown.

3. Dissolve 5 mg in 2 ml of water and add 3 drops of potassium dichromate (100 g/l) TS; a yellow precipitate is produced.

4. Dissolve 5 mg in about 1 ml of sucrose/hydrochloric acid TS and allow to stand for 5 minutes; a red colour is produced.

Degradation tests

Discoloration and a change in the physical state of the test substance usually indicate gross degradation.

GALLAMINE TRIETHIODIDE

Identity tests

Description. A white or almost white powder; odourless; hygroscopic.

Colour and other reactions

1. Dissolve 0.05 g in 5 ml of water and add 1 ml of potassio-mercuric iodide TS; a yellow precipitate is produced.

2. Dissolve 0.05 g in 5 ml of water and add 1 ml of sulfuric acid (~100 g/l) TS and 1 ml of potassium nitrite (100 g/l) TS; a brownish coloration is produced.

3. Dissolve 0.05 g in 5 ml of water and add 1 drop of nitric acid (~1000 g/l) TS and 1 ml of silver nitrate (40 g/l) TS; a yellow precipitate is produced which is insoluble in ammonia (~100 g/l) TS and nitric acid (~1000 g/l) TS.

HYDROCORTISONE SODIUM SUCCINATE

Identity tests

Description. A white or almost white, crystalline powder or amorphous solid; odourless; hygroscopic.

Colour and other reactions

1. Dissolve about 2 mg in 1 ml of alkaline potassio-mercuric iodide TS; a dark precipitate is produced.

2. Dissolve a small quantity in about 2 ml of sulfuric acid (~1760 g/l) TS; a yellow solution with a greenish fluorescence is produced. Very cautiously pour the solution into 10 ml of water; the colour of the solution changes to brownish yellow but the fluorescence remains.

3. Dissolve a small quantity in about 1 ml of phosphoric acid (~1440 g/l) TS and heat cautiously; a yellow solution is produced with a pale greenish fluorescence.

4. Dissolve about 2 mg in 1 ml of water and introduce the solution into a non-luminous flame using a magnesia stick or a nichrome or platinum wire sealed to a glass rod; the flame acquires an intense yellow colour.

5. Heat carefully 10 mg with 1 drop of water, 10 mg of resorcinol R and 3 drops of sulfuric acid (~1760 g/l) TS, cool and add 2 ml of water. Cool again and pour the solution into a mixture of 100 ml of water and 1 ml of sodium hydroxide (~400 g/l) TS; a yellowish green fluorescence appears.

Degradation tests

Discoloration of the substance and non-compliance with the following test usually indicate gross degradation:

Dissolve 0.20 g in 1.0 ml of water; a clear and colourless solution is produced.

KETAMINE HYDROCHLORIDE

Identity tests

Description. A white, crystalline powder; odour, characteristic.

Melting behaviour. About 260°C.

Colour and other reactions

1. Dissolve about 0.2g in 4 ml of water and chill the solution in ice. Add potassium carbonate (100 g/l) TS, drop by drop, until the solution is slightly alkaline when tested with pH-indicator paper R and allow to stand to crystallize. Filter and dry the crystals in a vacuum over phosphorus pentoxide R; melting temperature, about 92°C.

2. Dissolve 10 mg in 4 ml of water and add 0.5 ml of nitric acid (~130 g/l) TS and 0.5 ml of silver nitrate (40 g/l) TS; a white, curdy precipitate is produced. Separate the precipitate, wash it with water and add an excess of ammonia (~100 g/l) TS; the precipitate dissolves.

3. Dissolve 10 mg in 4 ml of sulfuric acid (~5 g/l) TS and add 1 drop of potassium iodobismuthate/acetic acid TS; a reddish brown precipitate is produced.

LEVAMISOLE

Identity tests

Description. A white, crystalline powder.

Melting point. About 59°C.

Colour reaction

Dissolve 0.05 g in 20 ml of water. Add 1 ml of sodium hydroxide (~80 g/l) TS, boil for 10 minutes and cool. Add a few drops of sodium nitroprusside (45 g/l) TS; a red colour is produced which fades with time.

LEVAMISOLE HYDROCHLORIDE

Identity tests

Description. A white to pale cream-coloured, crystalline powder; odourless or almost odourless.

Melting point. About 228°C.

Colour and other reactions

1. Dissolve 0.25 g in 20 ml of water and add 1.5 ml of sodium hydroxide (~80 g/l) TS. Extract with 20 ml of dichloromethane R, discard the aqueous layer and wash the dichloromethane layer with 10 ml of water. Discard the aqueous layer, shake the dichloromethane layer with about 1 g of anhydrous sodium sulfate R and filter. Evaporate the filtrate at room temperature and dry in a vacuum at a temperature not exceeding 40°C; the residue melts at about 59°C.

2. Dissolve 0.10 g in 40 ml of water. To 20 ml of this solution (keep the unused portion for test 3) add 1 ml of sodium hydroxide (~80 g/l) TS, boil for 10 minutes and cool. Add a few drops of sodium nitroprusside (45 g/l) TS; a red colour is produced which fades with time.

3. To 20 ml of the solution prepared for test 2 add 1 ml of nitric acid (~130 g/l) TS and a few drops of silver nitrate (40 g/l) TS; a white precipitate is produced. Separate the precipitate, wash with water and add an excess of ammonia (~100 g/l) TS; the precipitate dissolves.

MAGNESIUM SULFATE

Identity tests

Description. Brilliant, colourless crystals or a white, crystalline powder; odourless; effloresces in warm and dry air.

Colour and other reactions

1. Dissolve 10 mg in 2 ml of water and add 1 ml of ammonia (~100 g/l) TS; a white precipitate is produced. Add 1 ml of ammonium chloride (100 g/l) TS; the precipitate dissolves. Add 1 ml of disodium hydrogen phosphate (100 g/l) TS; a white precipitate is produced.

2. Dissolve 10 mg in 2 ml of water and add 3 drops of titan yellow TS and 2 ml of sodium hydroxide (~80 g/l) TS; a distinct pink colour is produced.

3. Dissolve 0.05 g in 5 ml of water. Add 1 ml of hydrochloric acid (~70 g/l) TS and 1 ml of barium chloride (50 g/l) TS; a white precipitate is produced.

MEDROXYPROGESTERONE ACETATE

Identity tests

Description. A white or almost white, crystalline powder; odourless or almost odourless.

Melting point. About 204°C.

Colour and other reactions

1. Dissolve 5 mg in 5 ml of sulfuric acid (~1760 g/l) TS. Incline the tube and carefully add, without mixing, 5 ml of ethanol (~750 g/l) TS; a blue-violet colour is produced at the interface of the two liquids.

2. Heat 0.05 g with 2 ml of potassium hydroxide/ethanol TS in a water-bath for 5 minutes. Cool and add 1 ml of water and about 1 ml of sulfuric acid (~1760 g/l) TS. Boil gently for 1 minute; ethyl acetate, perceptible by its odour (proceed with caution), is produced.

3. Dissolve 5 mg in 0.5 ml of methanol R in a small test-tube, add about 3 mg of sodium nitroprusside R, 0.05 g of sodium carbonate R and 0.5 g of ammonium acetate R and shake. Allow to stand for 10-30 minutes; a violet-red colour is produced (distinction from progesterone).

4. Dissolve a few crystals in about 1 ml of sulfuric acid (~1760 g/l) TS. Incline the tube and carefully add, without mixing, 1 ml of water; a green colour is produced at the interface of the two liquids. Allow to stand; the colour changes to bluish violet (distinction from hydroxyprogesterone caproate).

METHIONINE

Identity tests

Description. White crystals or a white, crystalline powder; odour, characteristic.

Colour and other reactions

1. Dissolve about 0.1 g in 5 ml of hydrochloric acid (0.1 mol/l) VS, add 0.2 ml of triketohydrindene/ethanol TS and heat; a violet colour is produced.

2. Dissolve 10 mg in 1 ml of water and add 1-2 drops of hydrochloric acid (~250 g/l) TS, 0.5 ml of copper(II) sulfate (1 g/l) TS and 1-2 ml of sodium hydroxide (~150 g/l) TS; a blue-violet colour is produced.

3. Dissolve about 0.1 g in 5 ml of potassium hydroxide (~110 g/l) TS and add about 0.3 ml of sodium nitroprusside (45 g/l) TS with shaking. Heat the solution in a water-bath at a temperature of 35-40°C for 10 minutes. Cool in ice for 2 minutes, add about 2 ml of hydrochloric acid (~250 g/l) TS and shake well; a red colour is produced.

METHYLROSANILINIUM CHLORIDE

Identity tests

Description. A dark green powder or greenish, glistening pieces with a metallic lustre; odourless or almost odourless.

Colour and other reactions

1. Add a few crystals to about 1 ml of sulfuric acid (~1760 g/l) TS and shake; an orange or brown-red coloured solution is produced. Cautiously dilute with water; the colour changes to brown, then to green and finally to blue.

2. Dissolve 20 mg in 10 ml of water and add 5 drops of hydrochloric acid (~420 g/l) TS. To 5 ml of this solution (keep the unused portion for test 3) add, drop by drop, tannic acid (100 g/l) TS; a blue precipitate is produced.

3. To the remaining solution from test 2 add 0.5 g of zinc R powder and warm the mixture; the solution discolours rapidly. On a filter-paper, place 1 drop of this solution adjacent to 1 drop of ammonia (~100 g/l) TS; a blue colour is produced at the zone of contact.

PENTAMIDINE ISETIONATE

Identity tests

Description. A white or almost white, crystalline powder; odourless; hygroscopic.

Melting point. About 190°C.

Colour and other reactions

1. To about 1 g add 10 ml of water and heat to 80°C to dissolve. Add 15 ml of sodium hydroxide (~80 g/l) TS, cool in ice and filter. To 2 ml of the filtrate (keep the unused portion for tests 2 and 3) add about 0.2 ml of nitric acid (~1000 g/l) TS and about 0.2 ml of ceric ammonium nitrate TS; a red-orange colour is produced.

2. Neutralize 5 ml of the remaining filtrate from test 1 with hydrochloric acid (~70 g/l) TS, testing with pH-indicator paper R, then add 3 ml of the same acid and a few drops of barium chloride (50 g/l) TS; no precipitate is produced.

3. Transfer a further 10 ml of the remaining filtrate from test 1 to a crucible, add 2.5 ml of hydrogen peroxide (~60 g/l) TS, mix and evaporate to dryness over a water-bath. Dissolve the residue in 1 ml of water, add about 1 ml of glacial acetic acid R, evaporate again and ignite until free from carbon. After cooling, add 5 ml of water and filter. If necessary, neutralize the filtrate with hydrochloric acid (~70 g/l) TS, testing with pH-indicator paper R, add 3 ml of the same acid, heat to boiling for 30 seconds, cool and add a few drops of barium chloride (50 g/l) TS; a white precipitate is produced which is practically insoluble in hydrochloric acid (~250 g/l) TS.

PENTAMIDINE MESILATE

Identity tests

Description. A white or light pink, granular powder; almost odourless.

Melting behaviour. About 265°C.

Colour and other reactions

1. To about 1 g add 10 ml of water and heat to 80°C to dissolve. Add 15 ml of sodium hydroxide (~80 g/l) TS, cool in ice and filter. To 2 ml of the filtrate (keep the unused portion for tests 2 and 3) add about 0.2 ml of nitric acid (~1000 g/l) TS and about 0.2 ml of ceric ammonium nitrate TS; a yellow colour is produced.

2. Neutralize 5 ml of the remaining filtrate from test 1 with hydrochloric acid (~70 g/l) TS, testing with pH-indicator paper R, and add 3 ml of the same acid and a few drops of barium chloride (50 g/l) TS; no precipitate is produced.

3. Transfer a further 10 ml of the remaining filtrate from test 1 to a crucible, add 2.5 ml of hydrogen peroxide (~60 g/l) TS, mix and evaporate to dryness over a water-bath. Dissolve the residue in 1 ml of water, add about 1 ml of glacial acetic acid R, evaporate again and ignite until free from carbon. After cooling, add 5 ml of water and filter. If necessary, neutralize the filtrate with hydrochloric acid (~70 g/l) TS, testing with pH-indicator paper R, add 3 ml of the same acid, heat to boiling for 30 seconds, cool and add a few drops of barium chloride (~50 g/l) TS; a white precipitate is produced which is practically insoluble in hydrochloric acid (~250 g/l) TS.

PREDNISOLONE SODIUM PHOSPHATE

Identity tests

Description. A white or almost white powder; odourless; hygroscopic.

Colour and other reactions

1. Dissolve about 2 mg in about 2 ml of sulfuric acid (~1760 g/l) TS and allow to stand for 5 minutes; a wine-red solution is produced. Dilute the solution very cautiously with 10 ml of water; the colour fades and a greyish brown, flocculent precipitate is produced.

2. Dissolve 5 mg in about 1 ml of phosphoric acid (~1440 g/l) TS and heat cautiously; the solution changes from colourless to yellow, then to orange and later to reddish brown.

3. Dissolve 10 mg in 1 ml of methanol R, add 1 ml of potassio-cupric tartrate TS and heat in a water-bath; an orange precipitate is gradually produced.

4. Carefully heat 0.04 g with about 2 ml of sulfuric acid (~1760 g/l) TS until white fumes are evolved. Add, drop by drop, nitric acid (~1000 g/l) TS until oxidation is complete. Allow to cool, add 10 ml of water and heat again until white fumes are evolved. Cool, add 10 ml of water and neutralize with ammonia (~100 g/l) TS, using pH-indicator paper R. Introduce an aliquot of this solution into a non-luminous flame using a magnesia stick or a nichrome or platinum wire sealed to a glass rod; the flame acquires an intense yellow colour. To the remaining solution add 5 ml of ammonium molybdate (95 g/l) TS, acidify with nitric acid (~130 g/l) TS and heat; a bright yellow precipitate is produced.

PYRIMETHAMINE

Identity tests

Description. A white, crystalline powder; odourless.

Melting point. About 240°C.

Colour and other reactions

1. Dissolve 0.05 g in 5 ml of sulfuric acid (~100 g/l) TS and add about 0.2 ml of freshly prepared potassio-mercuric iodide TS; a creamy white precipitate is produced.

2. To 1 ml of methyl orange/ethanol TS add 5 ml of water and 2 ml of ethyl acetate R and shake; the ethyl acetate layer remains colourless. Add a solution of 5 mg of the test substance dissolved in 5 ml of sulfuric acid (~5 g/l) TS, shake and allow to separate (about 30 minutes); a yellow colour is produced in the ethyl acetate layer.

3. Ignite about 0.1 g with 0.5 g of anhydrous sodium carbonate R, extract the residue with water and filter. Neutralize the filtrate with nitric acid (~130 g/l) TS and add 0.5 ml of silver nitrate (~40 g/l) TS; a white precipitate is produced. Add ammonia (~100 g/l) TS; the precipitate dissolves.

TAMOXIFEN CITRATE

Identity tests

Description. A white or almost white, crystalline powder.

Melting behaviour. About 142°C with decomposition.

Colour and other reactions

1. Shake 10 mg with 5 ml of dehydrated ethanol R. Add 3 ml of water, 0.5 ml of ammonia (~100 g/l) TS and 2 ml of phosphomolybdic acid/ethanol TS; within a few minutes the colour of the solution changes to light blue.

2. To 10 mg add 4 ml of pyridine R and about 2 ml of acetic anhydride R and shake; a yellow colour is immediately produced. Heat in a water-bath for 2 minutes; a light pink to red colour is produced.

VINBLASTINE SULFATE

Identity tests

Description. A white to slightly yellow, amorphous or crystalline powder; hygroscopic.

Note. This substance is very toxic and should be handled with care.

Colour and other reactions

1. To about 0.5 mg add 2 drops of a 10 mg/ml solution of ceric ammonium sulfate R in phosphoric acid (~1440 g/l) TS; a purplish red colour is produced which darkens with time.

2. To about 1 mg add 0.2 ml of a freshly prepared 10 mg/ml solution of vanillin R in hydrochloric acid (~420 g/l) TS; after about 1 minute a pink colour is produced (distinction from vincristine sulfate).

3. Mix about 0.5 mg with 5 mg of 4-dimethylaminobenzaldehyde R, about 0.2 ml of glacial acetic acid R and about 0.2 ml of sulfuric acid (~1760 g/l) TS; a reddish brown colour is produced which changes to pink after addition of about 1 ml of glacial acetic acid R.

4. Dissolve 10 mg in 2 ml of water. Add 1 ml of hydrochloric acid (~70 g/l) TS and 1 ml of barium chloride (50 g/l) TS; a white precipitate is produced which is practically insoluble in hydrochloric acid (~250 g/l) TS.

 

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